Investigations of the Origin of Stereocontrol in Syndiospecific Ziegler-Natta Polymerizations Citation Zubris, Deanna Lynn (2001) Investigations of the Origin of Stereocontrol in Syndiospecific Ziegler-Natta Polymerizations. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/j7gk-0s22. https://resolver.caltech.edu/CaltechTHESIS:03242014-152154971 Abstract In order to expand our understanding of the mechanism of stereocontrol in syndiospecific α-olefin polymerization, a family of Cs-symmetric, ansa-group 3 metallocenes was targeted as polymerization catalysts. The syntheses of new ansa-yttrocene and scandocene derivatives that employ the doubly [SiMe 2 ]- bridged ligand array (1,2-SiMe 2 ) 2 {C 5 H-3,5-(CHMe 2 ) 2 } (where R = t- butyl, tBuThp; where R = i-propyl, iPrThp) are described. The structures of tBuThpY(µ-Cl) 2 K(THF) 2 , tBuThpSc(µ-Cl) 2 K(Et 2 O) 2 , tBuThpYCH(SiMe 3 ) 2 , Y 2 {µ 2 -(tBuThp) 2 }(µ 2 -H) 2 , and tBuThpSc(µ-CH 3 ) 2 have been examined by single crystal X-ray diffraction methods. Ansa-yttrocenes and scandocenes that incorporate the singly [CPh 2 ]-bridged ligand array (CPh 2 )(C 5 H 4 )(C 13 H 8 )(where C 5 H 4 = Cp, cyclopentadienyl; where C 13 H 8 = Flu, fluourenyl) have also been prepared. Select meallocene alkyl complexes are active single component catalysts for homopolymerization of propylene and 1-pentene. The scandocene tetramethylaluminate complexes generate polymers with the highes molecular weights of the series. Under all conditions examined atactic polymer microstructures are observed, suggesting a chain-end mechanism for stereocontrol. A series of ansa-tantalocenes have been prepared as models for Ziegler-Natta polymerization catalysts. A singly bridged ansa-tantalocene trimethyl complex, Me 2 Si(η 5 -C 5 H 4 ) 2 TaMe 3 , has been prepared and used for the synthesis of a tantalocene ethylene-methyl complex. Addition of propylene to this ethylene-methyl adduct results in olefin exchange to give a mixture of endo and exo propylene isomers. Doubly-silylene bridged ansa-tantalocene complexes have been prepared with the tBuThp ligand; a tantalocene trimethyl complex and a tantalocene methylidene-methyl complex have been synthesized and characterized by X-ray diffraction. Thermolysis of the methylidene-methyl complex affords the corresponding ethylene-hydride complex. Addition of either propylene or styrene to this ethylene-hydride compound results in olefin exchange. In both cases, only one product isomer is observed. Studies of olefin exchange with ansa-tantalocene olefin-hydride and olefin-methyl complexes have provided information about the important steric influences for olefin coordination in Ziegler-Natta polymerization. Item Type: Thesis (Dissertation (Ph.D.)) Subject Keywords: Ziegler-Natta polymerizations ; Chemistry Degree Grantor: California Institute of Technology Division: Chemistry and Chemical Engineering Major Option: Chemistry Thesis Availability: Public (worldwide access) Research Advisor(s): Bercaw, John E. Thesis Committee: Grubbs, Robert H. (chair) Gray, Harry B. Rees, Douglas C. Bercaw, John E. Defense Date: 10 July 2000 Record Number: CaltechTHESIS:03242014-152154971 Persistent URL: https://resolver.caltech.edu/CaltechTHESIS:03242014-152154971 DOI: 10.7907/j7gk-0s22 ORCID: Author ORCID Zubris, Deanna Lynn 0000-0003-1003-9630 Default Usage Policy: No commercial reproduction, distribution, display or performance rights in this work are provided. ID Code: 8161 Collection: CaltechTHESIS Deposited By: Benjamin Perez Deposited On: 25 Mar 2014 16:34 Last Modified: 30 Nov 2022 00:39 Thesis Files Preview PDF - Final Version See Usage Policy. 51MB Repository Staff Only: item control page

Investigations of the Origin of Stereocontrol in Syndiospecific Ziegler-Natta Polymerizations Thesis by Deanna Lynn Zubris In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy Division of Chemistry and Chemical Engineering California Institute of Technology Pasadena, California 2001 (Submitted July 10, 2000) 11 © 2001 Deanna Lynn Zubris All Rights Reserved ill For Mom and Dad iv Acknowledgments My five years at Caltech have been a huge learning experience for me on both a scientific and personal level. This brief section expresses some of my gratitude for those who have helped me along the way. John Bercaw has helped me to learn a great deal of chemistry and really enjoy doing it by providing a challenging intellectual environment. Throughout my time at Caltech he has been a compassionate listener and friend and for this I will always be grateful. My committee members Bob Grubbs, Harry Gray, and Doug Rees have also provided helpful suggestions and advice. It was especially fun to organize Organometallics talks with Harry around to spice things up. I would also like to thank Gui Bazan, Rich Eisenberg and Bill Jones for urging me to consider Caltech for graduate school while I was an undergraduate at the University of Rochester. Starting out in the Bercaw group I was very fortunate to get teamed up with Tim Herzog. He showed me the ropes on the vacuum line and despite his tendency to store items out of my reach he was a great line mate and friend . Talking chemistry with Tim and Dario Veghini was invaluable to me as a new graduate student. Daria's charm, honesty, and sense of humor made him a wonderful confidant. Although I enjoyed having Shannon Stahl around for late night chats and his strong convictions regarding birthday celebrations, I admit that I was excited to assume his prime desk location when he finished at Caltech. And while Mike Abrams was initially apprehensive about sharing the Nook™ with a "chick", he seemed to really warm up to my lists of "things to be happy about". Mike also did a great job of helping me to pick out a monstrous pair of hiking boots and related gear for the group hike I attended with John, Dario, Chris and Jennifer Levy, and Arnel Fajardo. My labmates really defined my experience in the Bercaw group. I'm glad that Steve Miller was there to provide me with back-up on the softball field, as a fellow TA, and in the lab. Most of my ups and downs at Caltech were shared with Paul Chirik and I'm thankful for his genuine support and encouragement. Susan Schafer has been a great linemate and I'm pretty sure she doesn't realize how important her friendship was for maintaining my sanity in the lab. Chris Jones (Boss #3) was a fun addition to the lab and hopefully he won't tease my sister too much at Georgia Tech. Best of luck to my newest labmates, Sara Klamo and Endy Min. Also, best wishes to Lily Ackermann in her admirable v pursuit of group 5 ansa-rnetallocenes. Their fresh enthusiasm was a boost to me as I was in the horne stretch of my thesis work. My time in the Bercaw group has been shared with a very diverse group of people and I would like to acknowledge some of them here. I'm grateful for Chris (Theory) Brandow's upbeat attitude and ability to bring out the best in people. I appreciate John Scollard giving me a shoulder to cry on (often literally) and for supporting my love of Snoopy. Antek Wong-Foy was also there to lend me a hand when I needed it. Andy Kiely, Cory Nelson, Jim Gilchrist, Matt Holtcarnp, Jeff Yoder, Shigenobu Miyake, Ola Wendt, Seva Rostovstev, and Chris Levy are other "Hogs" who have helped me along the way. While not technically a "Hog" (due to an apparent aversion to softball) I've also had helpful talks with Joseph Sadighi. Caltech is a pretty incredible place to be a graduate student in part due to a few people who work hard to keep things running smoothly. Dian Buchness and Pat Anderson have both been very helpful and especially understanding when I needed to vent my frustrations. My time in the lab was a lot easier due to Rick Gerhart's ability to compensate for my clumsiness with a glass blowing torch and Mike Roy's assistance with blue box repairs. Larry Henling and Mike Day were helpful for obtaining X-ray diffraction data. Despite many ugly, misshapen crystals Larry still managed to provide me with all of the information I needed when I needed it along with well-timed, free snacks. I'm very grateful to my friends who have provided me with much needed breaks from the laboratory and helped to keep me grounded. The Caltech Masters Swim Club was a welcome reprieve after many tough days in the lab; Laurie and Dan Stein and coaches Kenny Grace and Mo Salama provided me with laughs and friendship . I've shared many of my grad school experiences with the "chick lunch" gang Aileen Kua, Claudine Chen, and Liz Krider. Aileen's thoughtful and kind nature and Liz's encouragement to "let my light shine" helped to keep me going. Magali Billen has been a caring friend through many of my tough times at Caltech and I hope that our paths cross again in the future. Fred Miller, Sarah Lorenz, and Kary Caccamise have been my constant cheerleaders and their friendship has helped me to believe in myself. Even though our lives are always moving in different directions I know they will always be my friends. Lastly I would like to acknowledge my parents, Donald and Sharon Zubris, and my sister Melissa for their constant support and love. I can't thank them enough for helping to me make it this far. vi Abstract In order to expand our understanding of the mechanism of stereocontrol in syndiospecific a-olefin polymerization, a family of Cs-syrnrnetric, ansa-group 3 metallocenes was targeted as polymerization catalysts. The syntheses of new ansa-yttrocene and scandocene derivatives that employ the doubly [SiMe2]bridged ligand array (1,2-SiMe2)2{CsH2-4-R}{CsH-3,5-(CHMe2hl (where R = tbutyl, tBuThp; where R = i-propyl, iPrThp) are described. The structures of tBuThpY(J.!-Cl)2K(THF)2, tBuThpSc(J.!-Cl)2K(Et20)2, tBuThpYCH(SiMe3)2, Y2{J..l2(tBuThp)2h(J..l2-Hh, and tBuThpSc(J.!-CH3)2Al(CH3)2 have been examined by single crystal X-ray diffraction methods. Ansa-yttrocenes and scandocenes that incorporate the singly [CPh2]-bridged ligand array (CPh2)(CsH4)(C13Hs) (where CsH4 = Cp, cyclopentadienyl; where C13Hs =Flu, fluorenyl) have also been prepared. Select metallocene alkyl complexes are active single component catalysts for homopolymerization of propylene and 1-pentene. The scandocene tetramethylaluminate complexes generate polymers with the highest molecular weights of the series. Under all conditions examined atactic polymer microstructures are observed, suggesting a chain-end mechanism for stereocon trol. A series of ansa-tantalocenes have been prepared as models for ZieglerNatta polymerization catalysts. A singly bridged ansa-tantalocene trimethyl complex, Me2Si(Y)5-Cs~)2TaMe3, has been prepared and used for the synthesis of a tantalocene ethylene-methyl complex. Addition of propylene to this ethylene-methyl adduct results in olefin exchange to give a mixture of endo and exo propylene isomers. Doubly-silylene bridged ansa-tantalocene complexes have been prepared with the tBuThp ligand; a tantalocene trimethyl complex and a tantalocene methylidene-methyl complex have been synthesized and characterized by X-ray diffraction. Thermolysis of the methylidene-methyl complex affords the corresponding ethylene-hydride complex. Addition of either propylene or styrene to this ethylene-hydride compound results in olefin exchange. In both cases, only one product isomer is observed. Studies of olefin exchange with ansa-tantalocene olefin-hydride and olefin-methyl complexes have provided information about the important steric influences for olefin coordination in Ziegler-Natta polymerization. vii Investigations of the Origin of Stereocontrol in Syndiospecific Ziegler-Natta Polymerizations TABLE OF CONTENTS Acknowled gm ents .......................................................................................................... iv Abs tract ............................................................................................................................. vi Table of Contents .......................... ................................................................................. vii Lis t of Figures ................................................................................................................ viii List of Tables ... .................................................................................................................. xi Chapter 1: Synthesis of C 5 - Symmetric Group 3 Metallocenes as Catalysts for a -Olefin Polymerization Ab stract. .................................................................................................................. l Introduction ...........................................................................................................2 Results and Discussion .......................................................................................... 8 Conclusions ............................. .............................................................................45 Exp erimental ........................................................................................................46 Chapter 2: Group 5 An sa-Metallocenes as Models for Ziegler-Natta Poly merization Cataly sts Abstract. ................................................................................................................ 64 Introduction .........................................................................................................65 Results and Discu ssion ........................................................................................71 Conclusion s ....................................................................................................... .100 Experimen tal ....... ............................................................................................... l Ol Appendix A: GPC Data ................................................................. .............................. ll6 Appendix B: X-ray Crystallographic Data ............................................................. 125 Vlll List of Figures Chapter 1: Figure 1. Various metallocenes (unlinked, singly bridged, and doubly bridged) and an ansa-monocyclopentadienyl-amido complex can be utilized as a-olefin polymerization catalysts .......................... ........................................................................2 Figure 2. C5 -symmetric singly linked cyclopentadienyl-fluorenyl cationic group 4 metallocenes serve as catalysts for the production of syndiotactic polypropylene .................................................................. ................................................. 3 Figure 3. Original proposed mechanism for formation of syndiotactic polypropylene ...................................................................................................................3 Figure 4. C5 -symmetry is not the only requirement for formation of syndiotactic polypropylene ...................................................................................................................3 Figure 5. Proposed transition state for propylene insertion into a growing polymer chain for a syndiospecific zirconocene catalyst ........................................... .4 Figure 6. C5-symmetric RThp zirconocene dichlorides, when activated with MAO, serve as highly active catalysts for the production of syndiotactic polypropylene ...................................................................................................................4 Figure 7. Essential features for formation of syndiotactic polypropylene ..............S Figure 8. C5 -symmetric yttrocenes and scandocenes are desired as catalysts for Ziegler-Natta polymerization ......................................................................................... 7 Figure 9. Calculations predict that neutral scandocene and cationic titanocene alkyl complexes have different preferences for the location of the alkyl substituent in the metallocene wedge ............................................................................ 7 Figure 10. A chain-end control mechanism may operate for C5 -symmetric group 3 metallocenes ............................................................................................................... .....8 Figure 11. Molecular structure of tBuThp Y(f.,t-Cl)2K(THF)2 .................................... 11 Figure 12. Molecular structure of tBuThpSc(f..t-Cl)2K(Et20)2 ................................... 13 Figure 13. Molecular structure of tBuThpYCH(TMS)2 ............................................. 19 Figure 14. Molecular structure of tBuThpYCH(TMS)2 ............................................. 20 Figure 15. Select atom labels for [Op YCH(TMS)2]. ...................................................21 IX Figure 16. Two types of dimeric ansa-yttrocene hydride complexes have been observed previously .......................................................................................................22 Figure 17. Molecular structure of [tBuThpYHh ........................................................ 24 Figure 18. Molecular structure of tBuThpSc(!l-Me)2AlMe2 ......................................29 Figure 19. Molecular structure of tBuThpSc(!l-Me)2AlMe2 ......................................30 Figure 20. Reaction of Cp2MMe2AlMe2 with pyridine provides different products forM = Y versus M = Sc .................................................................................31 Figure 21. Compounds tBuThpY(!l-Me)2AlMe2, tBuThpSc(!l-Me)2AlMe2, iPrThpSc(!l-Me)2AlMe2, EpSc(!l-Me)2AlMe2, and (tBuThp YCH(TMS)2 + H2) may be used as catalysts for a-olefin polyrnerization ........................................................ 39 Chapter 2: Figure 1. Metallocene symmetry exerts an influence on resulting poly(propylene) microstructure ................................................................................... 65 Figure 2. Doubly-silylene bridged zirconocenes favor 1,2-olefin insertion over 2,1-olefin insertion ........................................................................................................... 66 Figure 3. Proposed a-olefin insertion into yttrocene-hydride and yttrocenepolymer moieties ............................................................................................................ 67 Figure 4. A proposed transition state for a-olefin insertion into a growing polymer chain for a C5 -syrnrnetric, RThp metallocene ............................................. 67 Figure 5. Potential olefin insertion preferences into metal-hydride and metalpolymer bonds for C5 -syrnrnetric, RThp metallocenes .............................................68 Figure 6. Singly- and doubly-silylene linked tantalocene olefin-hydride and olefin-alkyl complexes are desired as model complexes for Ziegler-Natta polymerization catalysts ................................................................................................68 Figure 7. Cp2TaMe3 may be used as a synthetic precursor to the corresponding tantalocene ethylene-methyl complex ......................................................................... 70 Figure 8. [Cp*2TaMe2][BF4] may be used as a synthetic precursor to the corresponding tantalocene ethylene-hydride complex ............................................. 71 Figure 9. Molecular structure of SpTaMe3 .................................................................73 X Figure 10. General equation for equilibration of metallocene ethylene and propylene adducts ...... .......... ........................... ................................................................ 78 Figure 11. Examples of previously reported doubly-silylene bridged ansazirconocene dichloride complexes ................................................................................ 82 Figure 12. Doubly-silylene bridged ligand salts targeted for the synthesis of ansa-tantalocenes ............................................................................................................. 83 Figure 13. Both trans and cis relationships between the propylene methyl substituent and the ~-carbon of the polymer chain may be possible for olefin coordination ..................................................................................................................... 84 Figure 14. Invoking both a site epimerization mechanism and facile rotation about the a-carbon of the polymer chain may explain the atactic polymer formed using the RRp ligand array ..............................................................................87 Figure 15. Potential products from thermolysis of tBuRpTa(CH2)CH3................89 Figure 16. While tBuThpTaMe3 decomposes in ambient light, tBuThpTa(CH2)CH3 is stable. A bridged dinuclear complex is formed as a byproduct under select metallation conditions ..........................................................91 Figure 17. Molecular structure of tBuThpTaMe3·······················································93 Figure 18. Molecular structure of tBuThpTa(CH2)CH3 ...........................................94 Figure 19. Comparison of molecular structures of tBuThpTaMe3 and tBu Thp Ta( CH2)CH3........................................................................................................ 95 Figure 20. Conversion of tBuThpTa(CH2)CH3 to tBuThpTa(Y]2-CH2CH2)(H) may involve a tantalocene-ethyl complex as an intermediate .................................96 Figure 21. Difference NOE experiments indicate that (CH2=CHR'), where R' is methyl or phenyl, coordinates in an endo fashion with the R' substituent directed between the two isopropyl groups of the cyclopentadienyl ring ...........................99 Figure 22. Selectivity for olefin coordination exerted by the C5 -symmetric tBuThp ligand and the C2-symrnetric Bp ligand .......................................................lOO xi List of Tables Chapter 1: Table 1. Select bond distances and bond angles for potassium chloride adducts tBuThpY(!l-Cl)2K(THF)2 and tBuThpSc(!l-Cl)2K(Et20h ...........................................13 Table 2. Select bond distances and bond angles for tBuThp YCH(TMS)2 and Op YCH(TMS)2 ................................................................................................................. 20 Table 3. Select b ond distances and bond angles for dimeric yttrocene hydride complexes .........................................................................................................................23 Table 4. lH NMR resonances for bridging and terminal m ethyl substituents of select metallocene tetramethyaluminate complexes .................................................27 Table 5. Select bond distances and bond angles for m onomeric te tramethylaluminates tBuThpSc(!l-Me)2AlMe2 and Cp2Y(!l-Me)2AlMe2 .............29 Table 6. 1-pentene polymerizations ...........................................................................40 Table 7. Propylene p olymerizations .......................................................................... .40 Table 8. Polymerizations of 1-pentene and prop ylene ........................... ................ .41 Chapter 2: Table 1. Comparison of percent endo versus percent exo product for niobocene and tantalocen e propylene adducts .............................................................................. 77 Table 2. Equilibrium data for ethylene (R' = H) and propylene (R' = Me) adducts ..............................................................................................................................78 Table 3. Pentad analysis for polypropylene produced using catalyst tBuRpZrC12·················································· ..................................................................... 87 Table 4. Select bond distances and bond angles for tBuThpTaMe3 and tBuThpTa(CH2)CH3········································································································94 1 Chapter 1 Synthesis of Cs- Symmetric Group 3 Metallocenes as Catalysts for a-Olefin Polymerization Abstract The preparation of a series of C5-symmetric yttrocene and scandocene complexes incorporating the doubly (silylene-bridged) ligand array, (1,2SiMe2)2[4-R-CsH2][3,5-(CHMe2h-CsH] (RThp), is described. Reaction of K2RThp (where R = t-butyl or i-propyl) with MCb(THF)n (where M = Y, n = 3.5; M = Sc, n = 3) affords the corresponding metallocene chloride complexes tBuThpY(j.!Cl)2K(THF)n, tBuThpSc(j.!-Cl)2K(THF)n, and iPrThpY(j.!-Cl)2K(THF)n (where 0 ~ n ~ 2). The analogous scandocene bromide complex, iPrThpSc(j.!-Br)2K(THF)n, has also been prepared. Reaction of tBuThp Y(j.!-Cl)2K(THF)n with Nal and subsequent metathesis with KCH(SiMe3)2 provides a bis(trimethylsilyl)methyl yttrocene complex, tBuThp YCH(TMS)2. Hydrogenation of tBuThp YCH(TMS)2 provides a mixture of two dimeric yttrocene hydride complexes, Y{j.!(tBuThp)2(j.!-H)2}Y. One of these hydride complexes has been characterized by X-ray diffraction; each ligand array spans two metal centers in a "fly-over" dimeric structure. Combination of RThpM(j.!-X)2K(THF)n (where M = Y, Sc; R = tBu, iPr; X= Cl, Br) with LiAlMe4 affords the corresponding tetramethylaluminate complexes RThpM(j.!-Me)2AlMe2 (where M = Y, Sc; R = tBu, iPr). Scandocene and yttrocene tetramethylaluminate complexes that employ a singly linked cyclopentadienyl-fluorenylligand, [(C6Hs)2C{(T\5_ CsH4)(115-fluorenyl)}]M(j.!-Me)2AlMe2 (where M = Y, Sc), have been prepared via a similar methodology. Select tetramethylaluminate complexes serve as single component polymerization catalysts for the polymerization of 1-pentene and propylene. Use of these catalysts under a variety of conditions yields polymers with essentially atactic microstructures with a continuum of tacticities that range from a slight syndiotactic preference ([r] ""68%) to a slight isotactic preference ([m]"" 67%). This data is consistent with a chain-end control mechanism. These C5 symmetric group 3 catalysts follow a stereocontrol mechanism unlike what has been observed for analogous zirconocene catalysts. 2 Introduction The use of metallocenes as catalysts for ethylene and a-olefin polymerization is an area of intense investigation for academic and industrial chemists alike.l Homogeneous Ziegler-Natta catalysts (neutral group 3 and cationic group 4 metallocenes and their derivatives, see Figure 1) excel at the homopolymerization and copolymerization of these monomers. where M = Ti+, zr+, Sc, Y, La X= alkyl, H; E = C, Si; R =alkyl, aryl Figure 1: Various m etallocenes (unlinked, singly bridged, and doub ly bridged) and an ansamonocyclopentadienyl-amido complex can be utilized as a-olefin polymerization catalysts. The predictable correlation between metallocene structure and polypropylene tacticity is one of the most striking features of these polymerization catalysts.l In general, C2v-symmetric metallocenes produce atactic polypropylene, C2-symmetric metallocenes provide isotactic polypropylene, and select C1-symmetric metallocenes yield isotactic polypropylene, generally with less stereospecificity than what is observed with C2-symmetric catalysts. While a variety of metallocene catalysts have been reported for generation of isotactic polypropylene, the number of catalysts for production of syndiotactic polypropylene is limited. Ewen and Razavi first described the preparation of C5 -symmetric, singly-linked cyclopentadienyl-fluorenyl zirconocenes as syndiospecific polymerization catalysts. 2 Following this discovery a family of C5 -symmetric catalysts were synthesized for the production of syndiotactic polypropylene, as illustrated in Figure 2. 2,3 3 + where M = Zr, HJ; E = C, Si; R = CH3 , C 6H 5 Figure 2: C5 -symmetric singly linked cyclopentadienyl-fluorenyl cationic gro up 4 m e tallocenes serve as catalysts for the production of syndiotactic polypropylene. The mechanism first proposed by Ewen and Razavi2 for formation of syndiotactic polypropylene requires olefin insertions from alternating (enantiotopic) sides of the metallocene wedge. The authors also suggested that the methyl substituent of the propylene monomer would be directed away from the larger fluorenylligand. This mechanism is depicted in Figure 3. P \ _ jMe \ M I re \::::::= where M = z r+, Hf" Figure 3: Original proposed mechanism for formation of syndiotactic polypropylen e. Recent efforts in our group have helped to delineate the essential requirements for syndiospecific a-olefin polymerization catalysts. Two features of the singly linked cyclopentadienyl-fluorenyl catalysts, their C5 -symmetry and cyclopentadienylligands of differing sizes, were adopted in the zirconocene pictured in Figure 4.4 These two features were not sufficient for creation of a syndiospecific catalyst. Activation of this zirconocene with methylaluminoxane (MAO, 103 equivalents) in liquid propylene at 0°C provides essentially atactic polypropylene ([r] ~55%) . ~.--Cl (Me2 HChSi~~~r....._Cl ~SiMe3 SiMe3 Figure 4: C5 -symmetry is not the only requirement for formation of syndiotactic polypropylene . 4 Further consideration of the olefin insertion transition state described in Figure 3 suggested that the alkyl substituent of the incoming monomer may be oriented trans with respect to the ~-carbon of the polymer chain, as illustrated in Figure 5.4 This stereochemical assignment is supported by theoretical5 and experimental6 measurements of transition state geometry in related C2symmetric metallocenes. Incorporation of a C-H agostic assistance in the olefin insertion transition state7 is also consistent with this stereochemical assignment. :j: Figure 5: Proposed transition state for propylene insertion into a growing polymer cha in for a syndiospecific zirconocene catalyst. These observations were implemented in the design of a family of C 5 symmetric, doubly-silylene bridged ansa-zirconocenes, [(1,2-SiMe2h(115-4-RCsH2)(115-3,5-(CHMe2h-CsH)]ZrC12 (RThpZrCh, where R = H , iPr, tBu, TMS) for the production of highly syndiotactic polypropylene (Figure 6).4 These catalysts are notable for their high syndiospecificity, activity, and polymer molecular weights. For example, ThpZrCh (R =H) produces highly syndiospecific polypropylene ([rrrr] = 93.4% for ThpZrCh/MAO = 1 : 2000, in liquid propylene at 20°C) with high molecular weight (Mw = 1,300,000, PDI = 1.9). The highest syndiospecificity is found using iPrThpZrCl2 (iPrThpZrCh/MAO = 1: 2000, in liquid propylene at 20°C) where a [rrrr] value of 97.5% has been observed. MAO r r r r syndiotactic polypropylene Figure 6: C 5 -symmetric RThp zirconocene dichlorides, when activated with M AO, serve as highly active catalysts for the production of syndiotactic p o lypropylene . 5 From this work it appears that syndiospecific propylene polymerization catalysts operate via the general mechanism illustrated in Figure 7. Since both sides of the metallocene wedge are enantiotopic for a C5 -symmetric metallocene, regular migratory insertions from opposite sides of the metallocene wedge are required for syndiospecificity via enantiomorphic site control. One of the cyclopentadienylligands must have steric bulk flanking the metallocene wedge; this provides an open region to accommodate a propylene methyl group for olefin coordination and insertion. An a-agostic interaction in the transition state for olefin insertion may help enforce a trans relationship between the propylene methyl substituent and the ~-carbon of the polymer chain. r r r r Figure 7: Essential features for formation of syndiotactic polypropylene. A RThp metallocene has been u sed for illustrative purposes. 6 W hile these doubly-silylene bridged zirconocenes produce highly syndiotactic poly(a.-olefins) under high olefin pressure and low temperature conditions, polymerization under other conditions produces stereoerrors in the polymer microstructure. Examination of these errors reveals that site epimerization, polymer chain migration without insertion, is the predominant stereoerror forming mechanism (Scheme 1).8 Site epimerization disrupts regular migratory insertions from opposite sides of the metallocene wedge, and as a result syndiospecificity is lost. 1Rp -::¥zy- ... R n + ~ site epimerization R r diad R =./... fR~ ~ M--... ~ M = zr+; • = SiMe2 + ... m diad Scheme 1: Site epimerization is the principle stereoerror mechanism for RThp zirconocenes. In order to expand our understanding of the source of stereoerrors and mechanism of stereocontrol in syndiospecific a-olefin polymerization, we targeted a family of C5 -symmetric, ansa-group 3 metallocenes as polymerization catalysts (Figure 8). These target molecules are isoelectronic with cationic zirconocene catalysts. While group 3 metallocenes are typically less active polymerization catalysts than the analogous zirconocene cations, they have the advantage of being single component catalysts. 7 where M is Y or Sc and R is H or alkyl Figure 8: C5 -symmetric yttrocenes and scandocenes are desired as catalysts for Ziegler-Natta polymeriz ation. In contrast to cationic C5 -symmetric zirconocenes, theoretical studies predict that neutral C5 -symmetric yttrocene and scandocene complexes will not generate syndiotactic poly(a-olefins).9 Calculations indicate that a p endant alkyl substituent, such as a growing polymer chain, has an energetic preference to rest in a lateral position of the metallocene wedge for cationic group 4 metallocenes and rest in the central position of the wedge for neutral group 3 metallocenes (Figure 9) . Isoelectronic compounds with the general formula X2M-R were examined in this study (where X= Cl, (115-CsHs); M = Sc, Ti+; R = H , CH3, SiH3). 4?7 \ 4?7 \ + ~ ~ ~R ~ I Sc Sc-R Ti.._. R Figure 9: Calculations predict tha t neutral scandocene and cationic titanocene alkyl complexes have different preferences for the location of the alkyl substituent in the m e ta llocen e w ed ge. By extension, after each monomer insertion with a group 3 metallocene the growing polymer chain will relax to the central position of the metallocene wedge. The difference in transition state energies for olefin insertion may produce stereoregularity in the polymer microstructure if one transition state is energetically favored (Figure 10). Stereoregularity arising from a chain-end control mechanism contrasts our current understanding for generation of syndiotactic poly(a-olefins) with zirconocene catalysts, where regular alternation of monomer approach from different sides of the metallocene wedge yields syndiotactic polymer. These theoretical predictions provided further impetus for 8 preparation of C5-symmetric group 3 metallocenes to expand our understanding of stereocontrol in Ziegler-Natta polymerization. R R rR R\ ~M--.-- ~ r diad chain-end control mechanism • m diad Figure 10: A chain-end control mechanism may operate for C5 -symm etric group 3 metallocenes. Results and Discussion Preparation of yttrocene and scandocene RThp chloride complexes The tert-butyl substituted Thp ligand, [(1,2-SiMe2)2(4-CMe3-CsH2)(3,5(CHMe2h-CsH)] (tBuThp), was first targeted for the preparation of scandocene and yttrocene halide complexes. It was hoped that the bulky tert-butyl substituent would help prevent intermolecular C-H activation of the cyclopentadienyl ring by the electrophilic metal center, as has been observed previously (eq. 1).10 The most common synthetic route for the preparation of group 3 (Sc, Y, La) metallocenes is the reaction of deprotonated ligand salts with metal halides.ll For this reason, the dilithio and dipotassio tBuThp ligand salts, Lh[(1,2-SiMe2)2(4CMe3-CsH2)(3,5-(CHMe2h-CsH)] (2, LhtBuThp) and K2[(1,2-SiMe2)2(4-CMe3CsH2)(3,5-(CHMe2)2-CsH)] (3, K2tBuThp), have been synthesized (eq. 2). The dilithio ligand salt was prepared by addition of 2.2 equivalents of n-BuLi to a 0°C 9 diethyl ether solution of 1; complex 2 was isolated as a white powder in high yield. Combination of 1 and 1.90 equivalents of KN(SiMe3)2 in diethyl ether at -78°C and slow warming to 25°C affords the dipotassio ligand salt, 3; this compound has been isolated as an off-white powder in high yield. Examination of THF-ds solutions of 2 and 3 by lH NMR spectroscopy reveals that variable amounts of diethyl ether may be present in these samples; this coordinated solvent is taken into account for calculation of molecular weight. M~ /Me ..._, \ 2 s)::) ' \- < .· s· /~ ~ ~, KN(SiMe3h Et20 Me Me +isomers 1 3 In a similar fashion, K2iPrThp {K2[(1,2-SiMe2h(4-CHMe2-CsH2)(3,5(CHMe2)2-CsH)], 4} has been prepared by reaction of protio iPrThp with 1.90 equivalents of KN(SiMe3)2 (eq. 3). This ligand salt may be isolated as an offwhite powder in high yield. (3) Metallation of 2 was attempted by addition of THF to a mixture of 2 and YCb(THFhs at -78°C followed by slow warming to 25°C. Examination of the reaction product in THF-ds by lH NMR spectroscopy reveals that two C5 symmetric compounds are present. A variety of products are possible, such as solvent adducts (LnMCl(THF)x), dimeric complexes ((LnMC1)2), or salt adducts (LnM(!l-Cl)2Li(THF)x).ll Selective crystallization of one component of the reaction mixture has not been achieved. 10 In contrast, the dipotassio ligand salt 3 may be metallated with YCb(THFh5 to provide one isolated yttrocene product. Combination of 3 and YCl3(THF)3.5 and addition of THF at -78°C followed by slow warming to 25°C provides the salt adduct, [(1,2-SiMe2h(115-4-CMe3-C5H2)(115-3,5-(CHMe2hC5H)]Y(~-t-Cl)2K(THF)n (tBuThpY(~-t-Cl)2K(THF)n, 5), as the sole yttrocene product (eq. 4). Compound 5 has been analyzed by lH NMR spectroscopy in THF-ds and displays characteristic resonances for a C5 -symmetric, doublysilylene bridged metallocene. Two cyclopentadienyl resonances are present (in a 2: 1 ratio); two isopropyl methyl and two dimethylsilyl resonance are also observed. Variable amounts of protio THF are observed for different batches of 5 (0 ~ n ~ 2 equivalents); the amount of coordinated solvent may be quantified by comparison to integrations for ligand resonances. :: The presence of potassium in 5 has been supported by addition of 18crown-6 to a THF-ds solution of 5. This crown ether is known for its ability to solubilize cationic potassium. In the presence of 18-crown-6, the lH NMR resonances of 5 are shifted, suggesting coordination of potassium. The structural assignment of 5 has been confirmed by X-ray crystallography. Diffusion of pentane into a diethyl ether /tetrahydrofuran solution of 5 with slow cooling to -20°C affords colorless crystals that are suitable for X-ray diffraction, as illustrated in Figure 11. This structure is monoclinic and fits the P2Ifn space group. The ligand exhibits 115,115 cyclopentadienyl coordination with yttrium-cyclopentadienyl distances that are typical of RThp metallocenes.12 The potassium atom coordinates two molecules of THF, two bridging chlorides, and also displays 113-coordination to at-butyl substituted cyclopentadienyl ring of another molecule in the unit cell. The THF molecules have been modeled isotropically but their disorder appears to have little effect 11 on the remainder of the structure. Select bond distances and angles are given in Table 1. Figure 11: Molecular structure of 5 with selected atoms labeled (50% probability ellipsoids). Group 3 metallocene potassium chloride adducts are more rare than lithium chloride adducts.ll For example, prior work in our group suggested that use of dipotassio ligand salts, such as K2[(l-SiMe2)(2-SiMe3-4-CMe3-CsH2)2] (K2Bp ), may prevent formation a salt adduct upon metallation with YCb(THF)3.s.l3 Formation of a yttrocene potassium chloride adduct has been implicated previously, e.g., (115-CsMeshY(!-l-Cl)2K(THF)2, but an X-ray crystal structure is not available.1 4 The analogous cerium compound, (ll5-CsMes)2Ce(!-lCl)2K(THF)2, has been analyzed by X-ray diffraction; in this structure each potassium atom coordinates four chlorides and one THF molecule.lS Similar experiments were examined for preparation of tBuThp scandocene chloride complexes. Combination of ScCb(THF)3 and the dilithio ligand salt 2 provides a mixture of products, as evidenced by lH NMR spectroscopy. Attempts to selectively crystallize one component of the reaction mixture have not been successful to date. 12 The dipotassio ligand salt 3 may be employed for metallation with ScCl3(THF)3 to provide a single isolated scandocene product. Combination of 3 and ScCb(THF)3 and addition of THF at -78°C followed by slow warming to 25°C provides the salt adduct, [(1,2-SiMe2h(115-4-CMe3-C5H2)(115-3,5-(CHMe2hC5H)]Sc(f.l-Cl)2K(THF)n (tBuThpSc(f.l-Cl)2K(THF)n, 6) (eq. 5). Analysis of 6 by lH NMR spectroscopy in THF-ds reveals characteristic resonances for a C 5 symmetric, doubly-silylene bridged metallocene. Variable amounts of protio THF are observed for different batches of 6 (0::; n::; 2 equivalents) and the amount of solvent may be quantified by comparison to integrations for ligand resonances. Addition of 18-crown-6 to a THF-ds solution of 6 causes the lH NMR resonances to shift, thus supporting the presence of potassium in 6. Compound 6 has been analyzed by X-ray crystallography. Diffusion of petroleum ether into a diethyl ether solution of 6 with slow cooling to -20°C affords colorless crystals that are suitable for X-ray diffraction, as illustrated in Figure 12. This structure is triclinic and fits the P-1 space group. Standard 115,115 cyclopentadienyl coordination for RThp metallocenes is observed. The conditions for crystal growth appear to displace the coordinated THF (observed by lH NMR spectroscopy) with two coordinated diethyl ether molecules. The potassium atom coordinates two molecules of Et20 and three bridging chlorides; one of these chlorides is from another molecule in the unit cell. The diethyl ether molecules are disordered, but their disorder appears to have little effect on the remainder of the structure. Select bond distances and angles are g iven in Table 1. 13 Figure 12: Molecular structure of 6• Et20 with selected atoms labeled (50% probability ellipsoids). select bond distances (A) and bond an!(les (0 ) tBuThpY(j..t-Cl)2K(THF)2 tBuThpSc(j..t-Cl)2K(Et20)2 M-CpA M-CpB M-Cll M-Cl2 2.403 2.351(8) 2.391 2.587(2) 2.579(2) 115.0 80.7(3) 95.7(1) 2.2830(9) 2.4488(10) 2.5070(13) 122.71(3) 66.74(10) 94.52(4) CpA-M-CpB Pln.A-PlnB Cll-M-Cl2 Table 1: Select bond distances and bond angles for potassium chloride adducts tBuThpY(~­ Cl)2K(THF)2 and tBuThpSc(~-Cl)2K(Et20)2. An isopropyl functionalized Thp yttrocene chloride complex has been prepared by combination of the dipotassio ligand salt, K2iPrThp {K2[(1,2SiMe2)2(4-CHMe2-CsH2)(3,5-(CHMe2)2-CsH)], 4} with YCb(THF)3.s in THF. After two days of reaction at 25°C, the desired yttrocene chloride complex may be isolated (eq. 6). Characterization by lH NMR spectroscopy in THF-ds solvent reveals that the complex has C5-symmetry and that a non-stoichiometric amount of protio THF is present. The amount of coordinated protio THF may be 14 quantified by comparison to integrations of ligand resonances. This compound appears to be the potassium chloride adduct, [(1,2-SiMe2h(115-4-CHMe2CsH2)(115-3,5-(CHMe2h-CsH)]Y().l-Cl)2K(THF)n (iPrThpY(J.L-Cl)2K(THF)11, 7). Me\ - / Me s~K+; s·_).V\ 1\ Me Me Protio THF may be removed from yttrocenes 5 and 7 via a modified Soxhlet extraction, as described in the experimental section. Analysis of the products by lH NMR spectroscopy reveals that all protio solvent is absent following this procedure. Metallation of K2iPrThp with ScCh(THF)3 in THF does not provide the corresponding scandocene chloride under reaction conditions analogous to those for the preparation of 6. As a result, a related scandocene bromide complex has been synthesized (vide infra). Isolation of an unsubstituted Thp scandocene halide complex has not been achieved to date. Reaction of K2[(1,2-SiMe2)2(CsH3)(3,5-(CHMe2h-CsH)] (K2Thp) with ScCl3(THF)3 in THF-ds at 87°C provides a mixture of products and decomposition, as evidenced by lH NMR spectroscopy (eq. 7). Addition of excess Nal or NaBr to the reaction mixture also leads to decomposition. It is likely that intermolecular C-H activation of the unsubstituted cyclopentadienyl ring by scandium forms undesired products (e.g., eq. 1). Me\ - / Me s~K+ s·,JV 1\ Me Me ScC13 (THFh THF-d 8 87°C decomposition (7) 15 Preparation of yttrocene and scandocene RThp iodide and bromide complexes While yttrocene and scandocene chloride complexes tend to be synthesized most frequently, analogous bromide and iodide complexes have been reported.ll In some cases, bromide and iodide complexes may be prepared by chemical modification of known chloride complexes. For example, [(11S-1,3-SiMe3-CsH3)2]YI(THF) has been synthesized by addition of 2 equivalents of Nal to {[(115-1,3-SiMe3-CsH3)2]YClh in THF (eq. 8).16 Alternatively, deprotonated ligand salt (e.g., Li2tBuThp), MCIJ(THF)3 (where M = Y, Sc) and excess NaX (where X= Br, I) may be combined in one pot to yield the desired metallocene bromide or iodide complex. SiMe3 __&/ \ /THF Me3Si 2 y~ (8) ~I Me3Si~s·Me 1 3 Addition of THF to a mixture of tBuThp Y(!.!-Cl)2K(THF)n and 2 equivalents of Nal results in halide exchange after two days of stirring at 25°C (eq. 9). Analysis by lH NMR spectroscopy in THF-ds solvent reveals a 1 : 1 mixture of a C1-symmetric product and a C5-symmetric product. The presence of approximately 1 equivalent of protio THF suggests that the C1-symmetric product is an iodo-THF complex, [(1,2-SiMe2h(115-4-CMe3-CsH2)(115-3,5(CHMe2)2-CsH)]YI(THF) (tBuThpYI(THF), Sa). The C5 -symmetric product may be assigned as a dimeric yttrocene iodide complex with b ridging iodide ligands, {[(1,2-SiMe2)2(115-4-CMe3-CsH2)(115-3,5-(CHMe2)2-CsH) ]Y(!l-1) h {[tBuThp Y(!l-1) ]2, 8b}. 16 2 Nal Me2s~HF 5 _T_H_F---l•- MezSi~'_£........_1 - NaCl -KCl + Sa Other methods for preparation of tBuThp yttrocene iodide complexes are not as efficient as the procedure described in eq. 9. Heating a mixture of tBuThp Y(J..L-Cl)zK(THF)n and Nal in THF to 87°C induces some decomposition; similar results are obtained if dioxane-ds is used as a solvent. Combination of K2tBuThp, YCl3(THFhs, and excess Nal in THF-ds also provides some decomposition. Analogous reactions with NaBr as a halide source do not produce yttrocene bromide products. Further experimentation suggests that halide interconversion is highly dependent on the ligand and metal identity. Scandocene bromide or iodide complexes that employ the tBuThp ligand array cannot be isolated through the procedures described above. Addition of NaX to tBuThpSc(J..L-Cl)zK(THF)n in THF or combination of K2tBuThp, ScCl3(THF)3, and excess NaX in THF-ds does not yield the desired halide complexes. Boron triiodide is also ineffective for conversion of tBuThpSc(J..L-Cl)zK(THF)n to the corresponding iodide complex. Curiously, reaction of K2iPrThp, ScCb(THF)3, and excess NaBr in refluxing THF for four hours allows isolation of a scandocene bromide complex as an off-white powder (eq. 10). Analysis of the reaction product by lH NMR spectroscopy in THF-ds reveals C5 -symmetry of the product and the presence of protio THF. This is consistent with formation of a potassium bromide adduct, [(1,2-SiMe2h(115-4-CHMe2-CsH2)(115-3,5-(CHMe2h-CsH) ]Sc(J..L-Br)2K(THF)n (iPrThpSc(J..L-Br)zK(THF)n, 9). 17 Me\ - / Me s~K+; s·_).V"\ /~ THF Me Me Preparation of yttrocene alkyl and hydride complexes Alkyl substituents with significant steric bulk, such as bis(trimethylsilyl)methyl, are commonly used for the preparation of monomeric yttrocene and scandocene alkyls.ll The significant steric bulk prevents formation of dimeric alkyls which tend to be less reactive towards dihydrogen or a-olefins. The lack of~ hydrogens prevents decomposition of the alkyl complex via a ~-hydrogen elimination pathway. Addition of either LiCH(SiMe3)2 or KCH(SiMe3)z to tBuThp Y(!-lCl)zK(THF)n in toluene-ds provides decomposition, as evidenced by lH NMR spectroscopy. Slow addition of a toluene solution of LiCH(SiMe3)2 to a toluene solution of tBuThpY(!-l-Cl)2K(THF)n at -78°C, followed by slow warming to 25°C, also provides extensive decomposition. In contrast, combination of tBuThpYI(THF) / [tBuThpY(!-l-1)]2 (8a / 8b) and KCH(SiMe3)2, addition of toluene at -78°C, and slow warming to 25°C affords the desired monomeric alkyl complex, [(1,2-SiMe2h(TJ5-4-CMe3-CsH2)(TJ5-3,5(CHMe2h-CsH)]YCH(SiMe3h (tBuThpYCH(TMS)2, 10) (eq. 11). The product is isolated as an off-white powder by recrystallization from cold pentane. 18 Compound 10 has been analyzed by lH and 13C NMR spectroscopy in both benzene-d6 and toluene-ds solvent. Two C5 -symmetric species are evident. Variable temperature lH NMR spectroscopy from 196 to 356 K reveals that these two species are maintained in this temperature range. Two energetically preferred rotamers of the bis(trimethylsilyl)methyl substituent may be used to rationalize this observation, as illustrated in equation 11. This implies hindered rotation about the Y-C sigma bond. This phenomena has been observed for other singly-linked y ttrocenes, such as [Me2Si(115-CsMe4)2]YCH(SiMe3)2 [OpYCH(TMS)2)1 7 and [Me2Si(115_ CsMe4)(115-CsH4)]YCH(SiMe3)2. 18 For example, examination of OpYCH(TMS)2 by lH NMR spectroscopy reveals a single resonance for all six Si-CH3 groups of the CH(SiMe3)2ligand and two sets of (115-CsMe4) resonances at 25°C (300 MHz, benzene-d6). Again this signifies hindered rotation about the Y-C sigma bond. Colorless six-sided plates suitable for X-ray diffraction were precipitated from a toluene-ds solution of 10. This compound crystallized in the P21/n space group and its molecular structure appears in Figure 13. Atoms C25 and C26 exhibited some disorder during refinement. In fact C25 exists in two distinct conformations, with its attached hydrogen either up or down with respect to the metallocene wedge. The relative populations of C25A and C25B are 0.719(11) and 0.281(11), respectively. This contributes to the disorder of C26; it was most effectively modeled as a single anisotropic atom. The partial atom, C25A, was refined isotropically and is included in Figure 13. 19 Figure 13: Molecular structure of 10 with selected atoms labeled (50% probability ellipsoids). H y drogens omitted for clarity. The bonding of the bis(trimethylsilyl)methyl group in 10 is notable (Figure 14). There appears to be an interaction between the yttrium atom and a silicon carbon bond (Si4-C29). C25A seems to be shifted to the side of the metallocene wedge to facilitate this interaction. Select bond angles and bond distances for 10 are given in Table 2. 20 Figure 14: Molecular structure of 10 with selected atoms labeled (50% p robability ellipsoids). Select hydrogens omitted for clarity. select bond distances (A) and bond an_g]es n tBuThp YCH(TMS)2 OpYCH(TMS)2 Y-CpA Y-CpB Y-X1C Y-C25A/Y-C3 Y. .. C29/Y. ..C4 Si3-C25A-Si4/Si3-C3-Si2 2.394 2.386 2.806 2.437(4) 2.751(4) 118.5(2) 2.377 2.377 CpA-Y-CpB PlnA-PlnB 116.1 80.7(1) 2.418(7) 2.816(7) 122.8(3) 124.3 Table 2: Select bond distances and bond angles for tBuThpYCH(TMS)2 and OpYCH(TMS)2. The centroid of Si4 and C29 is assigned as XlC. 21 Figure 15: Select atom labels for [Me2Si(T]S-CsMe4)2]YCH(SiMe3)2 [OpYCH(TMS)2]_17 Related singly-linked bis(trimethylsilyl)methyl complex [Me2Si(115_ CsMe4)2]YCH(SiMe3)2 [Op YCH(TMS)2]1 7 (Figure 15) and the lutetium analog of [Me2Si(115-CsMe4)(115_CsH4)]YCH(SiMe3)218 have been analyzed by X-ray diffraction. Both complexes display a bridging M-(CH3)-Si interaction (where M = Y, Lu). This type of three center, two electron bridging interaction has been studied by Schaverien for other metallocenes.19 Hydrogenation of 10 in benzene-d6 solvent induces liberation of bis(trimethylsilyl)methane and generation of a mixture of two dimeric hydride complexes, as evidenced by lH NMR spectroscopy (eq. 12). The bridging yttrium hydrides of lla and 11b resonate as 1 : 2 : 1 triplets at 2.78 and 2.51 ppm with lJY-H values of 32.7 and 31.6 Hz, respectively. Each bridging hydride is coupled to two equivalent 89y nuclei (I= 1/2; 100% natural abundance) producing this characteristic splitting pattern. (12) 10 11b 22 Dimeric ansa-yttrocene hydride complexes of two types have been reported in the literature (Figure 16). Type I is more common that type II; th e latter is often referred to as a "flyover" dimer.ll Marks has d escribed the preparation of [Et2Si(115-CsMe4)(115-Cs~)YH]2 and su ggests that it is a type II dimer.18 The analogous lutetium complex, Lu{!l--[Et2Si(ll5-CsMe4)(1l5-CsH4)h(!l-H)2}Lu has been characterized by X-ray diffraction and possesses a type II coordination environment. 18 Conversion of the type I complex, [Me2Si(115_ CsMe4)2 YH]2, to the type II complex, Y{!l-2-[Me2Si(11 5-CsMe4)(115-CsMe4)h(!l-2H)2}Y throug h a "facile ligand redistribution" h as been reported .17 Our group has also reported type I compounds that do n ot generate the corresponding type II compounds over time, such as meso and rac-[Me2Si(115-2-SiMe3-4-AdCsH2)2Y(11--H)]2 ([Abp YH]2),20 [Me2Si(115-2-SiMe3-4-CMe3-CsH 2)2Y(11--H)]2 ([BpYH]2),21 and homo- and heterochiral [(OC10H6CloH60)Si(115-2-SiMe3-4CMe3-CsH2hY(11--H)]2 ([BnBpYH]2). 22 Proton NMR chemical shifts and lJy_H coupling constants for these y ttrocene hydrides are listed in Table 3. Bridging hydride ligands of both Type I and Type II complexes appear as 1 : 2 : 1 triplets due to coupling to two equivalent 89y nuclei. :£Rn Rnt > ' --H-......,.! .... H.......-r~ ,~ <$.\f Rn Rn I I· = ~ l\ .__ . H......_ I H..--Y "5'~\p Rn SiR21 Rn II Figure 16: Two types of dimeric ansa-yttrocen e hy dride complexes have been observed previou sly. 23 o(Y-H) lJy_H reference II 3.03 35.3 18 I 5.286 33.3 17 II 3.867 34.4 17 II? II I 2.78 2.51 4.65 32.7 31.6 31.1 * * I 31.3 31 20 I 4.76 4.87 I 4.98 31.4 22 I 5.97 31.4 22 compound type [Et2Si(115-CsMe4)(115 -CsH4)YH]2 [Me2Si(11 5-CsMe4)2YHh [Me2Si(11 5-CsMe4)2YHh lla llb [meso-Abp YHh [rae- Abp YHh [BpYHh homochiral [BnBpYHh heterochiral [BnBp YHh lH: 20 21 Tabl e 3: Select bond distances and bond angles for dimeric yttrocene h ydride complexes. * d enotes data from this work. Key structural information has been obtained from X-ray diffraction studies. X-ray quality crystals of llb were deposited from a benzene-d6 solution of lla and llb. The space group for these colorless square column crystals is P2If c. The molecule sits on a center of symmetry, so the unique bridging hydride was located by Direct methods. The yttrium hydride distance is 2.11(2) A. Notably, llb possesses a Type II, "flyover" dimeric structure where each tBuThp ligand array spans two yttrium atoms (Figure 17). The yttrium centroid distances are 2.2775(13) and 2.3594(15) A, respectively, and the centroid-yttriumcentroid angle for a single tBuThp ligand is 146.24(3t. 24 Figure 17: Molecular structure of llb with selected atoms labeled (50% p r obability ellipsoids). Hydrogens omitted for clarity. Dissolution of crystals of llb in toluene-ds and examination by lH NMR spectroscopy reveals that this "flyover" structure corresponds to the upfield hydride resonance at 2.51 ppm. Further NMR experiments have been directed at determining the structural identity of lla. Comparison of the bridging hydride lH chemical shifts listed in Table 3 suggests that lla may be a Type II, "flyover" dimer; Type I dimers tend to have more downfield chemical shifts for their hydrides. However, since lla incorporates a doubly-silylene bridged ligand comparison to singly-silylene bridged yttrocenes may not be valid. Additional structural evidence for both yttrocene hydride complexes has been obtained by NOE difference NMR spectroscopy. These studies provided additional support for the "flyover" nature of both lla and llb. The relative amounts of lla and llb formed during the course of hydrogenation (eq. 12) and subsequent equilibration of these dimers has been monitored by lH NMR spectroscopy. In related experiments other reagents have been added, such as dideuterium, trimethylphosphine, tetrahydrofuran, and a-olefins, to examine the effect on equilibration of lla and llb . 25 Hydrogenation of tBuThpYCH(TMS)2 has been examined by variable temperature NMR spectroscopy. Both yttrocene hydride compounds appear in approximately a 50: 50 ratio after 1 hour at 0°C. Over the course of 4 hours at this temperature, these compounds grow in intensity but maintain the same relative ratio. The yttrocene alkyl starting material is still present at this point. Upon warming the sample to 25°C for 1 week, an equilibrium ratio of yttrocene hydride compounds is reached (38 : 62 ratio, lla : llb ). When excess dihydrogen is removed, the product ratio remains the same. These results provide further support for a "flyover" structure of both lla and llb. Addition of dideuterium to an equilibrium mixture of lla and llb (38: 62 ratio) results in approximately 65% deuterium incorporation over the course of 48 hours, as evidenced by lH NMR spectroscopy. Removal of dideuterium and addition of dihydrogen provides complete restoration of the bridging hydride resonances. When 22 equivalents of ethylene is added to a benzene-d6 solution of lla and llb (38: 62 ratio), olefin is not consumed over the course of 12 hours at 25°C. The relative amount of llb increases upon ethylene addition, suggesting an associative pathway for the interconversion of lla and llb. Ethylene does not appear to react with these complexes since their lH NMR resonances are not altered in the presence of ethylene. Similar behavior is observed upon addition of excess PMe3 or THF to lla and llb (38: 62 ratio) in toluene-ds solvent; these reagents promote formation of llb. Upon removal of PMe3 or THF the altered lla: llb ratio is maintained with no observed chemical modification of either compound. Heating a benzene-d6 solution of lla and llb to 87°C also promotes equilibration of these compounds to generate increased amounts of llb. Since each yttrium of lla and llb has sixteen valence electrons, it is unclear why addition of cr-donor ligands such as PMe3 and THF promotes this equilibration. Synthesis of tetramethylaluminate complexes Unlinked group 3 metallocene tetramethylaluminate complexes of the form (TlS-CsHs)2M(f.l,-CH3)2Al(CH3)2 (Cp2MMe2AlMe2, where M = Y, Sc23) and 26 (11S-CsMes)2M(j.1-CH3)2Al(CH3h (Cp*zMMezAlMez, where M = Sm,24 Yb, Y25,26) have been reported previously. The unsubstituted complexes, CpzMMe2 AlMe2 (where M = Y, Sc), are prepared by reaction of [CpzMCl]z and LiAlMe4 in toluene (eq. 13). The monomeric yttrocene tetramethylaluminate complex, CpzYMezAlMez, has been analyzed by X-ray diffraction.23a The lH NMR resonances for bridging and terminal methyl substituents are diagnostic for tetramethylaluminate complexes. For the yttrocene compound, spectra acquired at -40°C reveal distinct bridging and terminal methyl resonances and at 40°C a single broad resonance is present for all methyl substituents. In contrast, the scandocene compound is static at 25°C, and distinct bridging and terminal methyl resonances are observed. ~ ....••''' M ··········· 2 equiv LiA1Me4 ~"c1 toluene 2 Use of the more sterically hindered bis-pentamethylcyclopentadienyl ligand array leads to formation of mixtures of monomeric and dimeric tetramethylaluminates. For example, Watson has described an equilibrium between monomeric Cp*zYMezAlMez and dimeric (Cp*zYMezAlMez)z, as illustrated in equation 14.25c Reaction of Cp*zYMezLi with AlMe3 affords these products. Teuben has also reported the preparation of these complexes via reaction of Cp*zYCl•THF and LiAlMe4 in toluene.26 At 20°C the monomer is dominant in solution; the monomer to dimer ratio is 4: 1. Watson has characterized this dimeric yttrocene by X-ray crystallography. (14) Lithium tetramethylaluminate has been utilized for conversion of the chloride complexes, 5 and 6, to the corresponding tetramethylaluminate complexes. Combination of either 5 or 6 with LiAlMe4 in toluene results in 27 alkylation; removal of toluene and extraction with pentane allows isolation of [(1,2-SiMe2h(TJ5-4-CMe3-CsH2)(TJ5-3,5-(CHMe2h-CsH)]M()l-CH3)2Al(CH3h (tBuThpMMe2AlMe2, where M = Y, 12; where M = Sc, 13) (eq. 15). Both 12 and 13 may be purified via recrystallization from pentane followed by addition of benzene and lyophilization. LiAlMe4 (15) toluene These tetramethylaluminate complexes have been analyzed by lH and 13C NMR spectroscopy. Due to the C5 -symmetry of these compounds, the bridging methyl substituents are chemically equivalent and the terminal methyl substituents are distinct. These methyl resonances are listed in Table 4 along with comparisons to previously reported tetramethylaluminate data. compound bridging Me terminal Me tBuThpYMe2AlMe2 -0.32 -0.35 -0.2 -0.32 -0.29 -17.6 -14.3 -0.61 -1.08 -0.506 -0.982 -0.33, -0.41 -0.23, -0.38 -0.09 -0.98 -0.84 1.63 -2.26 -0.47 -0.29 -0.218 -0.038 tBuThpScMe2AlMe2 Cp2YMe2AlMe2 Cp2YMe2AlMe2 Cp2ScMe2AlMe2 Cp*2SmMe2AlMe2 [Cp*2SmMe2AlMe2]2 Cp*2YMe2AlMe2 [Cp*2YMe2AlMe2h Cp*2YMe2AlMe2 [Cp*2YMe2AlMe2h solvent benzene-d6 benzene-d6 toluene-ds CD2Cb CD2Cb benzene-d6 benzene-d6 toluene-ds toluene-ds toluene-ds toluene-ds temp. 25°C 25°C -45°C -45°C 25°C 25°C 25°C 20°C 20°C -40°C -40°C ref. * * 23 23 23 24 24 26 26 25 25 Table 4: lH NMR resonances for bridging and terminal methyl substituents of select metallocene tetramethyaluminate complexes. Both monomeric and dimeric complexes are tabula ted where appropriate. * denotes data from this work. 28 As previously noted, metallocene tetramethylaluminate complexes may exist in monomeric or dimeric form. To probe the molecularity of 12 and 13 variable temperature lH NMR spectroscopy was used for characterization. NMR spectra were acquired in a temperature range from 200 to 340 K; no evidence was obtained for a monomer-dimer equilibrium in either case. For yttrocene 12, the three chemically distinct methyl resonances coalesce at -0.45 ppm at 338 K. This has also been observed for Cp2YMe2AlMe2.23c Coalescence of bridging and terminal methyl resonances may b e attributed to dissociation of a bridging methyl substituent, rotation about the remaining yttrium-methyl bond, and recoordination of an aluminum bound methyl substituent. This sequence for equilibration of methyl substituents is illustrated in Scheme 2. Scheme 2: Bridging and terminal m e thyl substituents may be equivalenced by this series of equilibrium reactions. In contrast, scandocene 13 displays three methyl resonances that remain distinct throughout the temperature range examined. Equilibration of bridging and terminal methyl resonances is not observed on the NMR time scale. Further evidence for the monomeric nature of 13 has been obtained by Xray crystallography. Slow cooling of a solution of 13 afforded colorless crystals that were suitable for X-ray diffraction, as illustrated in Figure 18. The space group is PI. The aluminum displays a nearly tetrahedral arrangement o f methyl substituents. The tert-butyl substituent appears to exert a small steric influence 29 on the coordination environment of aluminu m; the alu minum is found 0. 1 A below the plane formed by scand ium and the bridging carbon atoms (C25 and C26). Select bond distances and bond angles are given in Table 5. c 12 c 28 C21 c 22 ® ~~::JI.---{1;~ C 23 Si I c 27 Figu re 18: Molecular structure of 13 w ith selected atoms labeled (50% probability ellipsoids). Hydrogen atoms are omitted for clarity. select bond distances (A) and bond an~les (0 ) tBuThpSc(J.t-Me)2AlM€2 Cp2Y(J.t-Me)2A1Me2 M-CpA M-CpB M -C25/M-C1 M-C26/M-C2 C25-M -C26/C1-M-C2 C25-Al-C26 I C1-Al-C2 C 27-Al-C28/C3-Al-C4 CpA-M-CpB PlnA-PlnB 2.239(1) 2.233(1) 2.442(2) 2.414(2) 88.48(8) 108.73(9) 113.13(10) 123.53(3) 75.68(7) 2.62(2) (average) 2.62(2) (average) 2.57(2) 2.60(2) 85(1) 112(1) 111(1) Table 5: Select bond distan ces and bond angles for monomeric tetramethylaluminates tBuThpSc(11--Me)2AlMe2 and Cp2Y(11--Me)2AlMe2.23b 30 Hydrogen atoms H25C and H26C are 2.21(2) and 2.19(2) A from scandium, respectively, suggesting bonding interactions (see Figure 19). These agostic C-H interactions have been observed in o ther metallocenes7 but have not been noted for tetramethylaluminate complexes to date. Figure 19: Molecular str ucture of 13 with selected atoms labeled (50% probability ellipsoids). The analogous iPrThp scandium tetramethylalurninate complex may be prepared from combination of the scandocene bromide precursor, iPrThpSc(J...LBr)2K(THF)n, with LiAlMe4 in toluene (eq. 16). Removal of toluene and extraction with pentane allows isolation of [(1,2-SiMe2h(Tl5-4-CHMe2-CsH2)(Tl53,5-(CHMe2h-CsH)]Sc(J.l-CH3)2Al(CH3h (iPrThpScMe2AlMe2, 14) . Like 12 and 13, complex 14 may be purified via recrystallization from pentane followed b y addition of benzene and lyophilization. LiA1Me4 toluene (16) 31 Reactivity of tetramethylaluminate complexes Addition of pyridine to Cp2MMe2AlMe2 (where M = Y, Sc) has been reported previously.27 When 1 equivalent of pyridine (pyr) is added to Cp2YMe2AlMe2, it coordinates AlMe3, and a dimeric yttrocene methyl compound is formed. In contrast, 1 equivalent of pyridine coordinates the scandium of Cp2ScMe2AlMe2 yielding a scandocene methyl-pyridine complex and 0.5 equivalents of [AbMe6] (Figure 20). Similarly, addition of THF to Cp2ScMe2AlMe2 affords the corresponding methyl-THF compound. Removal of pyridine from Cp2ScMe(pyr) in vacuo provides an unidentified product. ~ .....•"'" ~~e 2 ~,,,,pyr S~ + 0.5 [Al Me ~Me 2 6] Figure 20: Reaction of Cp2MMe2AlMe2 with pyridine provides different products for M= Y versus M = Sc. Addition of 1 equivalent of pyridine to tBuThp YMe2AlMe2 in benzene-d6 provides approximately 66% conversion to a C1-symmetric species, as evidenced by lH NMR spectroscopy. The ligand and pyridine resonances are consistent with formation of a methyl-pyridine compound, as illustrated in eq. 17. When additional pyridine is added to drive this reaction to completion, decomposition occurs. pyridine 12 Me2S~yr pyridine Me2Si~Me -----il- decomposition (17) + 0.5 [Al2Me6] 32 When 1 equivalent of pyridine is added to tBuThpScMe2AlMe2 in benzene-d6, a C1-symmetric species forms initially and a C5 -symmetric species grows in over the course of 24 hours. Analysis by lH NMR spectroscopy reveals that the initial product may be a methyl-pyridine adduct and the second product a dimeric methyl complex (eq. 18). 13 + pyr-AlMe 3 Strauss and Grubbs have utilized 4-dimethylaminopyridine (DMAP) as a stoichiometric trap for AlMe2CL28 The insolubility of DMAP-AlMe2Cl in pentane was designed as a driving force for the reaction described in equation 19. ~ \ ,,,, ,,,, Ti'··' N Q NMe2 CH2=CHR ······ R /.~ ~ + (19) Addition of approximately 1 equivalent of DMAP to tBuThpYMe2AlMe2 in benzene-d6 solution provides a mixture of products, as evidenced by lH NMR spectroscopy. At least one C1- and one C 5 - symmetric product are present. Notably, all of the starting yttrocene was consumed. However, when this reaction was attempted on a preparative scale, extensive d ecomposition occurred. The reactivity of the yttrocene and scandocene products described in eq. 17 and eq. 18 towards propylene has been examined. Addition of 1 equivalent of pyridine and 10 equivalents of propylene to tBuThpMMe2AlMe2 (where M = Y, 33 Sc) in benzene-d6, does not lead to olefin consumption, as evidenced by lH NMR spectroscopy (eq. 20). Over the course of three days at 25°C, negligible propylene is consumed and additional metallocene products are formed that were not observed in the propylene-free reactions. Addition of stoichiometric pyridine does not enhance the reactivity of tBuThpMMe2AlMe2 (where M = Y, Sc) towards a-olefins, such as propylene. H /CH3 ····Al Me2Si~d1:~~ 'cH3 3 C 11,, M e2S 1 r J 10equiv . pyn.d.1ne 1 equtv multiple m etallocene products whereM = Y , Sc Methylaluminoxane has also been examined as a potential additive to enhance the reactivity of tBuThpMMe2AlMe2 (where M = Y, Sc) towards aolefins. However, addition of MAO(::: 100 equivalents) to tBuThpMMe2AlMe2 (where M = Y, Sc) in combination with propylene (in benzene-d6) or 1-pentene (neat) does not lead to olefin consumption. Preparation of linked cyclopentadienyl-fluorenyl complexes The dilithio ligand salt, Li2[Ph2C(Csf4)(C13Hs)] (Li2Ep)29 h as been utilized for the preparation of C5-symmetric yttrocene and scandocene complexes. Metallation of Li2Ep with YCl3(THFhs in THF affords the dimeric y ttrocene chloride complex, {[Ph2C(11S-CsH4)(11S-C 13Hs) ]YCll2 [(Ep YC1)2, 15] as a bright yellow solid (eq. 21). The lH NMR spectrum of 15 is consistent with this structural assignment; no protio THF is present and the product exhibits C5symmetry. (21) (20) 34 Metallation of Li2Ep with ScCl3(THF)3 in THF provides the monomeric scandocene complex, [Ph2C(11S-CsH4)(11S-C13Hs)]ScCl(THF) [EpScCl(THF), 16] as a bright yellow solid (eq. 22). Analysis of 16 by lH NMR spectroscopy in THF-ds reveals that one equivalent of protio THF is present. Since 16 appears to be C5 symmetric, the THF may be dissociating and recoordinating to scandium at a rate that is fast relative to the NMR time scale. (22) 16 Combination of either 15 or 16 with excess LiAlMe4 provides the corresponding tetramethy lal uminate complexes, [Ph2C (115-CsH4)(11SC13Hs)]M(J..1-CH3hAl(CH3h (where M = Y, EpYMe2AlMe2, 17; where M = Sc, EpScMe2AlMe2, 18], respectively (eq. 23). These complexes have been isolated via Soxhlet extraction with pentane solvent; low solubility of 17 and 18 in pentane results in low isolated yields. H3 LiA1Me4 toluene ' ......,c '''·· ....-CH3 (23) - M·.......,C.,.Al.......CH %, H 3 3 M = Y, 17 M = Sc, 18 Both 17 and 18 have been characterized by lH NMR spectroscopy in benzene-d6 solution at 25°C. Yttrocene 17 displays a broad resonance at -1.2 ppm that corresponds to all four yttrium-methyl resonances, both bridging and terminal. Scandocene 20 displays three distinct scandium methyl resonances; the bridging methyls are found at -1.83 ppm and the terminal methyls are found at -0.52 and -0.55 ppm. 35 Polymerization of a-olefins The yttrocene and scandocene alkyl and hydride complexes described above have been tested as potential catalysts for a.-olefin polymerization. Both small scale (:o::: 15 mg metallocene) and preparative scale(""' 300 mg metallocene) reactions have been carried out to examine the efficiency of olefin consumption. When ethylene (:o::: 100 equivalents) is added to a benzene-d6 solution of the yttrium tetramethylaluminate compound, tBuThp YMe2AlMe2 (12), it is consumed rapidly as evidenced by lH NMR spectroscopy. The increased viscosity of the solution and the lH NMR spectrum suggest formation of polyethylene. Addition of a.-olefins such as propylene or 1-hexene (:o::: 100 equivalents) to this yttrocene yields no measurable olefin consumption after weeks at 25°C. In contrast, when 1-hexene (= 40 equivalents) is added to a benzene-d6 solution of the related scandocene compound, tBuThpScMe2AlMe2 (13), olefin is completely consumed within 4 hours at 25°C. Analysis by lH NMR spectroscopy reveals that 1-hexene oligomers have formed. From these experiments it appears that 13 is more reactive towards a.-olefins than 12. A proposed mechanism for a.-olefin insertion into a tetramethylaluminate complex of the form RThpMMezAlMez (where M = Y, Sc) is given in Scheme 3. Presumably when aluminum does not share bridging methyl substituents with the metallocene, trimethylaluminum may dissociate readily. This dissociation is shown in Scheme 3 when the olefin CH2=CHR' coordinates to the metallocene. Throughout the course of polymerization, AlMe3 may be associated with the metallocene between olefin insertions. These mechanistic issues are currently under investigation with singly-linked and unlinked scandium tetramethylaluminate complexes.30 36 . dR Me Me:'siQ~ M S ~ olefin insertion R'------~- Scheme 3: Proposed mechanism for a-olefin insertion with compounds of the form RThpMMe2AlMe2. Compound 13 also serves as an effective hydrocyclization catalyst for a -co dienes. Addition of 1,5-hexadiene (::::::50 equivalents) to a toluene-ds solution of 13 under dihydrogen affords a mixture of cyclized and uncyclized products (eq. 24). The relative amounts of methylcyclopentane and hexane were ascertained by gas chromatography. Combination of 1,6-heptadiene (::::::50 equivalents) and 13 in benzene-d6 under dihydrogen affords a mixture of cyclized and uncyclized products (eq. 25). The relative amounts of methylcyclohexane and heptane were measured by gas chromatography. For both reactions, conversion to produ cts is complete within approximately 24 hours. 13 + ~ H2 : : : 50 equiv. toluene-d8 0 +~(24) 6 + 3.64 13 H2 +~ benzene-d6 ::::::50 equiv. 1 1 ~ 26.1 (25) 37 Yttrocene compounds tBuThp YCH(TMS)2 (10) and [tBuThp YHh (11a/11b) are less reactive towards ethylene and a-olefins than their tetramethylaluminate counterparts. When ethylene (:::o: 5 equivalents) is adde d to a benzene-d6 solution of 10 no olefin consumption is observed over the course of 12 hours at 25°C. Similarly, addition of ethylene (:::o: 5 equivalents) to a benzened6 solution of 11a/ 11b results in no olefin consumption over the course of 12 hours at 25°C. Addition of a-olefins such as propylene or 1-pentene (100 equivalents) to 11a/ 11b yields no measurable olefin consumption after weeks at 25°C. When 11a/ 11b are exposed to neat 1-butene ("" 860 equivalents) for five d ays at 25°C, no isolable polymer is formed. Combination of 10 and approximately 5200 equivalents of n eat 1-pentene d oes n ot provide isolable polymer after one week at 25°C. Successful p oly m erization of 1-pentene was achieved b y in situ generation of the corresponding yttrium h ydride species; when 10 is exposed to neat 1-pentene ("" 8100 equivalents) under a dihydrogen atmosphere, poly(pentene) is isolated after 7.5 days at 25°C. The observed lack of reactiv ity of 10 and 11a/ 11b towards a-olefins and the requirement for in situ generation of a yttrium hydride species m ay b e rationalized by Schemes 4 and 5. Scheme 4 d elin eates a mechanism for a-olefin insertion into the bis(trimethylsilyl)methyl complex, 10. Unfavorable steric interactions between the bulky bis(trimethylsilyl)methyl substituent and an incoming a-olefin (CH2=CHR') may hinder olefin coordination and subsequent insertion. Coordination and insertion of CH2=CHR' may be more facile for relate d tetramethylaluminate complexes since loss of trimethylaluminum m ay reduce the steric hindrance at the metal center (Scheme 3). 38 R' :=/ Scheme 4: Proposed mechanism for a-olefin insertion for tBuThpYCH(TMS)2. Scheme 5 describes a-olefin coordination and insertion with a monomeric yttrocene hydride intermediate. Previous studies have suggested that a monomeric hydride species is required for polymerization of a -olefins.31 The steric hindrance for olefin coordination and insertion is negligible as compared to what is described in both Scheme 3 and Scheme 4. However, dimerization of the monomeric yttrocene hydride may compete with olefin insertion, thus reducing the rate of propagation. In situ hydrogenation of 10 may be n ecessary to generate a working concentration of monomeric [tBuThp YH] th at is necessary for propagation. 39 R' =:=/ ~e2S~ ~e Si~'-~''''\. 2 13-H elim. tI tI . olefi~ msertlon Scheme 5: Proposed mechanism for a-olefin insertion for in situ formed [tBuThpYH]. The metallocenes illustrated in Figure 21 have been utilized for polymerization of 1-pentene and propylene. Tetramethylaluminate complexes 12, 13, 14, and 18 serve as single component polymerization catalysts. Dihydrogen gas (4 atm) was added to 10 to promote the polymerization of 1pentene (vide supra) . Select reaction conditions and full pentad distributions for these polymers are listed in Tables 6 and 7. where R = tBu: M = Y, 12; M = Sc, 13 where R = iPr: M = Sc, 14 Figure 21: Compounds 12, 13, 14, 18, and (10 + H2) may be used as cata lysts for a-olefin poly merization. "<:ji 0 20 0 9 hr 2 hr 10.75 hr 64.5 89.0 37.5 50.7 25.39 20.81 22.64 8.90 9.49 25.40 28.40 30.20 29.03 24.68 23.84 25.79 27.68 27.36 27.24 28.17 26.22 25.26 [rmmr] [mmmm] [mmmr] [mmrm] 5.16 10.34 6.54 8.28 7.30 21 .29 25.03 [rrrr] [mrmr] 7.84 7.79 8.38 9.15 8.30 12.57 11.78 [mrrr] 3.92 7.18 3.80 4.60 4.55 6.35 4.52 [mrrm ] 66.86 33.18 59.23 40.81 64.39 35.51 61.69 38.62 62.76 37.26 47.92 52.12 48.31 51.73 [r] 0 2 hr 4.8 21.62 27.85 [m] 21 7.5 d 8.6 29.45 entry catalyst T(°C) duration % yield 22 7.5 d 49.9 2 3 4 [mmrr] [rmmr] 13 13 14 14 12 22 24 hr by mass 5 10 +H2 21 1 6 18 4 hr* 3 hr 1 hr 10.67 hr 3.76 2.07 1.44 1.9 0.62 11.91 11.17 7.96 6.93 6.56 4.24 9.4 7.85 8.35 7.43 6.98 6.35 4.87 12.37 11 .7 12.02 10.62 10.92 9.78 8.6 27.28 26.93 28.1 25.82 27.12 24.39 21.58 14.35 14.19 14.48 14.21 13.96 13.97 13.83 5.9 5.18 5.38 11.19 11.34 12 16.4 11.49 11.02 11.22 15.48 16.23 17.64 19.41 4.38 6.23 5.52 5.21 5.09 7.42 10.45 51.22 48.77 51.14 48.84 50.58 49.42 42.79 57.21 41.35 58.66 38.88 61.13 31.74 68.26 [r] 2.5 hr 4.97 11.1 [rmrr] 1 hr 3.72 - 4 hr* [m] 7 Table 6: 1-pentene polymerizations. 18 13 13 13 14 14 14 entry cat. duration [mmmm] [mmmr] [rmmr] [mmrr] [mrmm] [mrmr] [rrrr] [mrrr] [mrrm ] 1 2 3 4 5 6 7 Table 7: Propylene polymerizations. *denotes polymerization with a 50/ 50 (v / v) mixture of propylene and toluene. "<:ti rl 18 13 13 13 13 13 14 14 14 10 + H2 14 14 12 18 propylene propylene propylene propylene 1-pentene 1-pentene propylene propylene propylene 1-pentene 1-pentene 1-pentene 1-pentene 1-2entene -5 -5 -5 -5 20 0 -5 -5 -5 22 21 0 22 21 10.67 hr 1 hr 3 hr 4 hr* 2 hr 10.75 hr 2.5 hr 1 hr 4 hr* 7.5 d 2 hr 9 hr 7.5 d 24 hr entry catalyst monomer T(°C) duration 1 2 3 4 5 6 7 8 9 10 11 12 13 14 [m] [r] 31.74 68.26 38.88 61.13 41.35 58.66 42.79 57.21 47.92 52.12 48.31 51.73 50.58 49.42 51.14 48.84 51.22 48.77 59.23 40.81 61.69 38.62 62.76 37.26 64.39 35.51 66.86 33.18 Mn (x 103) Mw (x 103) 86.0 - 195 - - - 32.1 - - M w/Mn 2.3 2.5 2.6 2.9 2.0 1.9 - 7.5 - 1.9 2.0 13.4 4.5 9.3 16.0 3.9 - 5.5 10.5 34.0 11.6 26.7 - 2.9 5.3 Table 8: Polymerizations of 1-pentene and propylene. *denotes polymerization with a 50/50 (v /v) mixture of propylene and toluene. 42 A comparison of the [m] and [r] diad content for these 1-pentene and propylene polymerizations is summarized in Table 8. Polymer molecular weight information is also provided when available. The scandium tetramethylaluminate complexes 13, 14, and 18 display the highest polymer molecular weights of the series; this is notable since scandocene complexes generally dimerize a-olefins.32 In general, the scandocenes, 13, 14, and 18, are more active polymerization catalysts than yttrocenes, 12 and (10 + H2). A proposed mechanism for a-olefin insertion, chain propagation, and termination with tetramethylaluminate compounds of the form RThpMMe2AlMe2 (where M = Y, Sc) is provided in Scheme 6. Use of these catalysts under a variety of conditions yields polymers with essentially atactic microstructures with a continuum of tacticities that range from a slight syndiotactic preference ([r] ""'68%) to a slight isotactic preference ([m]""' 67%). Changes in polymerization temperature or monomer dilution appear to exert little influence on polymer tacticity, within experimental error. For a given catalyst, the [r] diad content is larger for the polypropylene it produces versus polypentene. This effect is most striking for catalyst 18; it forms the most syndiospecific polypropylene and the most isospecific polypentene of the series. This tacticity data is consistent with the chain-end control mechanism depicted in Scheme 7, where small differences in transition state energies for olefin insertion may provide some stereoregularity in the polymer microstructure. Since relaxation of the polymer chain to the central position of the metallocene wedge appears to be fast relative to olefin insertion, stereocontrol is not derived from regular alternating olefin insertion. These C5 symmetric group 3 catalysts appear to follow a chain-end control mechanism unlike the mechanism of stereocontrol for analogous zirconocene catalysts. ~ C0 ' , R .. Me Me,S~'Me,. Af Me • ~~e R' elim. AlMe, , Me I , /=1M-Me-Al ~R . R • OR MezS~M;::Me . I olefin insertion Me2Si~-y\R' 2 R 1 Me2Si~~p Mezsr~ dRR' HdR' Me I tf 4 Me,s~HMe ~-H MezSr~.L Me2Si~~R' •Me Si~~R' Me,Si~ ., Me,St R' ,..,____ _ Me,Si~'Me"" 'Me "' R Me2S~11 Me2Si~ _ HdR ===< Me2Si~R Me2Si~~"R' Scheme 6: Proposed mechanism for a-olefin polymerization with tetrame thylaluminate compounds of the form RThpMMe2AlMe2. ~ ~ R .. R ~ ~' -f¥~p ~ ~ • :t: . R :t: ~ p-df~ . 'kirsi IT~~ Scheme 7: Rapid site epimerization may induce a chain-end mechanism for stereocontrol. R ~ R 45 Conclusions A series of C5 -symmetric yttrocene and scandocene hydride and alkyl complexes have been prepared as single component catalysts for a-olefin polymerization. Yttrocene and scandocene chloride complexes that employ the doubly-silylene bridged ligand array, [(1,2-SiMe2h(4-CHMe2-CsH2)(3,5(CHMe2)2-CsH)] (tBuThp), have been synthesized and characterized by X-ray diffraction. Both compounds exist as potassium chloride adducts with ethereal solvent coordinated to potassium (tetrahydrofuran or diethyl ether, respectively). The related complexes iPrThpY()l-Cl)2K(THF)n and iPrThpSc()lBr)2K(THF)n have been prepared as well. A yttrocene alkyl complex, tBuThp YCH(TMS)2, has been synthesized by combination of tBuThp Y()lCl)2K(THF)n with Nal and subsequent metathesis with KCH(SiMe3)2. This yttrocene alkyl compound has been characterized by X-ray crystallography; its structure displays an interaction between yttrium and one of the silicon-carbon bonds of the bis(trimethylsilyl)methyl substituent. Hydrogenation of tBuThp YCH(TMS)2 provides a mixture of two dimeric yttrocene hydride complexes, Y{)l-(tBuThp)2()l-H)2}Y. One of these hydride complexes has been analyzed by X-ray diffraction; each ligand array spans two metal centers in a "flyover" dimeric structure. Reaction of RThpM()l-X)2K(THF)n (where M = Y, Sc; R = tBu, iPr; X = Cl, Br) with LiAlMe4 affords the corresponding tetramethylaluminate complexes RThpM()l-Me)2AlMe2 (where M = Y, Sc; R = tBu, iPr). Scandocene and yttrocene tetramethylaluminate complexes that employ a singly linked cyclopentadienyl-fluorenylligand, [(C6Hs)2C{(115_ CsH4)(115-fluorenyl)}]M()l-Me)2AlMe2 (where M = Y, Sc), have been synthesized using a similar methodology. Select tetramethylaluminate complexes serve as single component catalysts for polymerization of propylene and 1-pentene. In situ generation of [tBuThpYH] provides an active species for polymerization of 1-pentene. The scandium tetramethylaluminate complexes display higher polymerization activities and produce higher polymer molecular weights than the yttrocene catalysts. Overall these catalysts produce polymers with essentially atactic microstructures under a variety of conditions. Polymer tacticities range from a slight syndiotactic preference ([r] "" 68%) to a slight isotactic preference ([m] "" 67%). This tacticity data is consistent with a chain-end control mechanism. The 46 polymer chain appears to relax to the central position of the metallocene wedge at a rate faster than olefin insertion. Therefore, stereocontrol is not derived from regular alternating olefin insertion. The C5-symmetric group 3 catalysts described herein follow a stereocontrol mechanism unlike that of analogous zirconocene catalysts. These metallocenes have expanded our understanding of stereocontrol for syndiospecific a-olefin polymerizations. Experimental General Considerations. All air or moisture sensitive chemistry was performed using standard high vacuum line or Schlenk techniques, or in a dry box under a nitrogen atmosphere as described previously.33 Dinitrogen, dihydrogen, and argon were purified by passage over MnO on vermiculite and activated molecular sieves. Petroleum ether and toluene were distilled from sodium and stored under vacuum over titanocene.34 Tetrahydrofuran and diethyl ether were distilled from sodium benzophenone ketyl. Pyridine was distilled from CaH2 immediately b efore use. 1-hexadiene and 1-heptadiene were distilled from LiAll-4 immediately before use. Benzene-d6 was distilled from LiAll-4 and then distilled from sodium sand before use. Tetrahydrofuran-ds was distilled from sodium benzophenone ketyl and stored over 4A molecular sieves. Methylene chloride-d2 was distilled from calcium hydride. Ethylene was purchased from Matheson and passed through a dry ice/ acetone trap before use. Propylene was purchased from Aldrich and stored under vacuum over triisobutylaluminum. MAO (methylaluminoxane, Albemarle) was prepared by removing toluene in vacuo; the white MAO solid was dried at 25°C for 48 hours at high vacuum. LiCH(TMS)2 was prepared by the method of Cowley .35 Potassium bis(trimethylsilyl)amide (KN(TMS)2) was sublimed before use. Lb[Ph2C(CsH4)(C13Hs)] (Li2Ep) was prepared as described by Razavi. 29 ScCl3(THF)3 and YCl3(THFhs were prepared according to literature methods.36 Protio RThp ligands, (1,2-SiMe2)2(4-R-CsH3)(3,5-(CHMe2h-CsH2) (where R = tBu, iPr), were synthesized as described previously. 4 All dilithio and dipotassio ligand salts were prepared via standard procedures37 unless otherwise noted. All other reagents were purchased from Aldrich and u sed as received or purified using standard methods.38 47 Instrumentation. NMR spectra were recorded on a Bruker AM500 (lH, 500.13 MHz; 13C, 125.77 MHz) spectrometer, a Joel GX-400 (lH, 399.78 MHz; 13C 100.53 MHz; 19F, 376.1 MHz) spectrometer, a G.E. QE300 (lH, 300.1 MHz) spectrometer, a Varian !NOVA 500 (lH, 500.13 MHz; 13C, 125.77 MHz) spectrometer, or a Varian 300 (lH, 300 MHz) spectrometer. All chemical shifts are relative to TMS for lH (residual) and 13C NMR (solvent used as a secondary standard). Nuclear Overhauser (NOE) difference experiments were conducted using a Varian INOVA 500 MHz spectrometer. Elemental analysis was performed at the California Institute of Technology Elemental Analysis Facility by Fenton I. Harvey or at Midwest Microlab in Indianapolis, Indiana. X-ray crystallography was carried out by Dr. Michael W . Day and Lawrence M. Henling using an EnrafNonius CAD-4 diffractometer. Small crystalline fragments were cut under Paratone-N oil and mounted on the diffractometer under a stream of cold N 2 gas. Li2[(1,2-SiMe2h(4-CMe3-CsH2)(3,5-(CHMe2h-CsH)] (2). (Li2tBuThp). In the dry box a 100 mL round bottom flask was charged with [(1,2-SiMe2)2(4-CMe3CsH3)(3,5-(CHMe2h-CsH2)] (2.21 g, 5.74 mmol) and attached to a fine porosity swivel frit assembly. On the vacuum line, diethyl ether (50 mL) was added by vacuum transfer. The -78°C cold bath was replaced with a ooc ice water bath and the apparatus was backfilled with argon. A cannula was threaded through the side arm of the swivel frit and then n-BuLi (9.0 mL, 12.60 mmol, 2.2 equiv, 1.4 M in hexanes) was added dropwise via a syringe. When addition was complete, the cannula was removed and replaced with the Kontes valve and the reaction was left open to the mercury bubbler to slowly warm to 25°C. After 24 hr of stirring, diethyl ether was removed in vacuo, petroleum ether (50 mL) was added by vacuum transfer, and the reaction mixture was stirred for 30 minutes. Petroleum ether was removed in vacuo, then fresh petroleum ether (50 mL) was added by vacuum transfer. A yellow supernatent was filtered away from a white solid and washed with recycled petroleum ether (2 x 40 mL). The petroleum ether was removed in vacuo and the white solid was dried under high vacuum for 4 hr; 2.49 g (89.7%). lH NMR (THF-ds): 8 = 0.27 (s, 12H, broad (CH3)2Si), 1.21 (d, 12H, (CH3)2CH, J = 6.8), 1.27 (s, 9H, (CH3)3C), 3.13 (m, 2H, (CH3)2CH, J = 6.8), 5.92 (s, 1H, Cp-H), 6.12 (s, 2H, Cp-H). 48 K2[(1,2-SiMe2h(4-CMe3-CsH2)(3,5-(CHMe2h-CsH)] (3). (K2tBuThp). In the dry box a 250 mL round bottom flask was charged with [(1,2-SiMe2)2(4-CMe3CsH3)(3,5-(CHMe2)2-CsH2)] (3.55 g, 9.20 mmol) and KN(TMS)2 (3.49 g, 17.5 mmol, 1.90 eq) and attached to a fine porosity swivel frit assembly. On the vacuum line, diethyl ether (150 mL) was added by vacuum transfer. A few minutes after the addition of diethyl ether, the solution becomes cloudy. The -78°C cold bath was removed to allow the reaction to slowly warm to 25°C. The apparatus was backfilled with argon and stirred for 12 hr. A yellow supernatent was filtered away from an off-white solid and washed with recycled diethyl ether (4 x 100 mL). After removing diethyl ether in vacuo, petroleum ether (75 mL) was added by vacuum transfer and used to wash the solid three additional times. Petroleum ether was removed in vacuo and the off-white solid was dried under high vacuum for 6 hr with heating to 50°C; 3.80 g (89.6%). lH NMR (THF-ds): 8 = 0.13 (s, 12H, broad (CH3)2Si), 1.14 (d, 12H, (CH3)2CH, J = 6.77), 1.27 (s, 9H, (CH3)3C), 3.05 (m, 2H, (CH3)2CH, J = 6.30), 5.71 (s, 1H, Cp-H), 5.97 (s, 2H, Cp-H). K2[ (1,2-SiMe2h(4-CHMerCsH2)(3,5-(CHMe2h-CsH)] (4). (K2iPrThp ). Compound 4 is prepared in an analogous manner to 3 by the reaction of [(1,2SiMe2)2(4-CHMe2-CsfL!)(3,5-(CHMe2h-CsH3)] (4.69 g, 12.6 mmol) with KN(SiMe3)2 (4.78 g, 23.9 mmol, 1.90 equiv) in diethyl ether (125 mL). The resulting suspension was allowed to slowly warm to 25°C while stirring for 12 hr. The white solid was isolated on a fine frit and washed with diethyl ether (3 x 50 mL) and then with petroleum ether (3 x 50 mL). The solvent was removed in vacuo and the solid dried under high vacuum for 6 hr with heating to 50°C to provide a white powder; 4.87 g (86.5%). [(1,2-SiMe2h(115-4-CMe3-CsH2)(115-3,5-(CHMe2h-CsH) ]Y(f.l-Cl)2K(THF)n (5). (tBuThpY(f.l-ClhK(THF)0 ). In the glove box, a 200 mL flask was charged with 3 (3.49 g, 7.58 mmol) and YCb(THF)3.s (3.39 g, 7.58 mmol) and attached to a fine porosity swivel frit assembly. On the vacuum line, tetrahydrofuran (125 mL) was added by vacuum transfer while stirring at -78°C, and then this cold bath was replaced by a ooc ice water bath and the reaction was allowed to slowly warm to 25°C while stirring. After 72 hr of reaction, solvent was removed in vacuo and the solid dried under high vacuum for 12 hr. Diethyl ether (100 mL) was added to the reaction flask via vacuum transfer to give a pale tan slurry; a pale tan solid was filtered away from the orange supernatant and washed with 49 recycled solvent (3 x 75 mL). Solvent was removed in vacuo and the solids dried under high vacuum for 12 hr. Petroleum ether (100 mL) was added to the flask containing the orange diethyl ether soluble material by vacuum transfer to yield an off-white solid precipitate and a pale yellow solution. This off-white solid was filtered away from the supernatant and washed with recycled petroleum ether (4 x 75 mL). Solvent was removed in vacuo and hexane (50 mL) was added for two additional solid washings. Solvent was removed in vacuo and the off-white product was dried under high vacuum for 12 hr; 2.44 g (51.3%). 1H NMR (THFds): o= 0.56 (s, 6H, (CH3)2Si), 0.69 (s, 6H, (CH3)2Si), 0.99 (d, 6H, (CH3)2CH, J = 6.9), 1.21 (d, 6H, (CH3)2CH, J = 6.6), 1.27 (s, 9H, (CH3)3C), 1.78 (m, ~0.25H, protio THF), 2.90 (m, 2H, (CH3)2CH, J = 6.7), 3.62 (m, ~0.25H, protio THF), 5.75 (s, 1H, Cp-H), 6.32 (s, 2H, Cp-H). lH NMR (CD2Cb): o= 0.54 (s, 6H, (CH3)2Si), 0.76 (s, 6H, (CH3)2Si), 1.02 (d, 6H, (CH3)2CH, J = 6.8), 1.18 (d, 6H, (CH3)2CH, J = 5.7), 1.23 (s, 9H, (CH3)3C), 1.82 (broad, ~2H, protio THF), 2.75 (broad, 2H, (CH3)2CH), 3.68 (broad, protio THF), 5.83 (s, 1H, Cp-H), 6.34 (s, 2H, Cp-H). 13H NMR (THF-ds): o = 0.68, 5.29 ((CH3)2Si), 22.75, 30.42 ((CH3)2CH, (CH3)2CH, overlapping peaks), 33.33, 33.98 ((CH3)3C, (CH3)3C), 106.46, 116.77, 121.61, 139.61, 154.23 (Cp). Analysis Calculated (Found) C: 52.91 (53.04); H: 7.03 (7.63). Note regarding preparation- amount of protio THF present in product varies from run to run, and is quantified by integration of protio THF resonances as compared to ligand resonances in the 1H NMR spectrum. Addition of 18-crown-6 (excess) to this sample yields: 1H NMR (THF-ds): o= 0.59 (s, 6H, (CH3)2Si), 0.65 (s, 6H, (CH3)2Si), 0.99 (d, 6H, (CH3)2CH, J = 6.9), 1.21 (d, 6H, (CH3)2CH, J = 6.6), 1.27 (s, 9H, (CH3)3C), 2.97 (m, 2H, (CH3)2CH, J = 6.77), 5.70 (s, 1H, Cp-H), 6.33 (s, 2H, Cp-H). Removal of protio THF from 5. Tetrahydrofuran was removed from 5 via a modified Soxhlet extraction, similar to a method utilized previously.39 In the g love box, 5 (0.80 g) was placed in a 150 mL round bottom flask and attached to a Soxhlet extractor. A glass thimble (fitted with coarse frit) was filled 3 I 4 full with 10 A activated molecular sieves and carefully placed inside the Soxhlet extractor. A condenser and 180° needle valve were attached and the apparatus was removed from the glove box. Toluene (100 mL) was added to the round bottom flask by vacuum transfer and then the apparatus was closed to dynamic vacuum. The solution was stirred at 25°C and the condenser cooled to -30°C with a methanol cooling unit to begin the Soxhlet extraction. After 24 hr, the 50 flask was attached to a fine porosity swivel frit assembly, toluene was removed and hexane (50 mL) was added via vacuum transfer to provide a white slurry. A white solid was filtered away from a yellow supernatant; the product was washed with recycled hexane (2 x 30 mL) and dried under high vacuum for 12 hr; 0.49 g. 1H NMR (THF-ds): same chemical shifts as 5 but no protio THF present. [(1,2-SiMe2)2(1l5-4-CMe3-CsH2)(1l5-3,5-( CHMe2)2-CsH) ]Sc(~-t-ClhK(THF)n (6). (tBuThpSd~-t-ClhK(THF)n). In the glove box, a 100 mL flask was charged with 3 (2.80 g, 6.07 mmol) and ScCl3(THF)3 (2.23 g, 1 equiv) and a fine swivel frit assembly was attached. On the vacuum line, tetrahydrofuran (60 mL) was added by vacuum transfer while stirring at -78°C, and then this cold bath was replaced by a 0°C ice water bath and the reaction was allowed to slowly warm to 25°C while stirring. After 4.5 days of reaction at 25°C, solvent was removed in vacuo to leave a brown sludge which was dried under high vacuum for 12 hr. Diethyl ether (60 mL) added to the reaction flask by vacuum transfer to provide a pale brown slurry. A pale tan solid was filtered away from a red-orange supernatant and the solid washed with recycled solvent (6 x 30 mL). Diethyl ether was removed in vacuo and petroleum ether (50 mL) was added by vacuum transfer. The slurry was stirred for 1 hr and then the solvent was removed in vacuo and the solid dried under high vacuum for 12 hr. Petroleum ether (50 mL) was added by vacuum transfer to the flask containing the orange diethyl ether soluble material. Next, a pale tan precipitate was filtered away from the supernatant and washed with recycled petroleum ether (3 x 30 mL) . Solvent was removed in vacuo and hexane was added for three additional solid washings. Solvent was removed in vacuo and the pale tan product was dried under high vacuum for 12 hr; 1.21 g (36.0%). 1H NMR (THF-ds): 8 = 0.54 (s, 6H, (CH3)2Si), 0.68 (s, 6H, (CH3)2Si), 0.98 (d, 6H, (CH3)2CH, J = 7.0), 1.19 (d, 6H, (CH3)2CH, J = 6.6), 1.28 (s, 9H, (CH3)3C), 1.77 (m, -1H, protio THF), 2.86 (m, 2H, (CH3)2CH, J = 6.72), 3.62 (m, -1H, protio THF), 5.81 (s, 1H, Cp-H), 6.29 (s, 2H, Cp-H). 13H NMR (THF-ds): 8 = -0.55, 4.33 ((CH3)2Si), 21.82, 26.43, 28.99, 29.17, 32.77 ((CH3)2CH, (CH3)3C), 110.11, 113.56, 119.94, 128.03, 140.31, 156.54 (Cp). Note regarding preparation- amount of protio THF present in product varies from run to run, and is quantified by integration of protio THF resonances as compared to ligand resonances in the 1H NMR spectrum. Addition of 18-crown-6 (excess) to this sample yields: 1H NMR (THF-ds): 8 = 0.57 (s, 6H, (CH3)2Si), 0.65 (s, 6H, (CH3)2Si), 0.98 (d, 6H, (CH3)2CH, J = 7.0), 1.22 (d, 6H, 51 (CH3)2CH, J = 6.6), 1.29 (s, 9H, (CH3)3C), 2.91 (m, 2H, (CH3)2CH, J = 4.66), 5.79 (s, lH, Cp-H), 6.31 (s, 2H, Cp-H). [(1,2-SiMezh(115-4-CHMerCsHz)(115-3,5-(CHMezh-CsH)]Y(J.1-Cl)zK(THF)n (7). (iPrThpY(J.l-Cl)zK(THF)n). Compound 7 is prepared in an analogous manner to 5 by the reaction of 4 (824 mg, 1.84 mmol) with YCIJ(THFhs (826 mg, 1 equiv) in tetrahydrofuran (50 mL). After 48 hr of reaction at 25°C, solvent was removed in vacuo, petroleum ether (50 mL) was added b y vacuum transfer, and the resulting slurry was stirred for 2 hr. The solvent was removed in vacuo and the solid dried under high vacuum for 12 hr. Diethyl ether (40 mL) was added by vacuum transfer to provide a pale tan slurry; a pale tan solid was filtered away from an orange supernatant and washed with recycled solvent (3 x 30 mL). Solvent was removed in vacuo and the solids dried under high vacuum for 12 hr. Petroleum ether (25 mL) was added via vacuum transfer to the flask containing the orange diethyl ether soluble material, resulting in precipitation of an offwhite solid from the yellow-orange solution. This off-white solid was filtered away from the supernatant and washed with recycled petroleum ether (3 x 20 mL). Solvent was removed in vacuo and hexane (20 mL) was added by vacuum transfer for two additional solid washings. Hexane was removed in vacuo and the off-white product was dried under high vacuum for 9 hr; 0.70 g (65.0%). lH NMR (THF-ds): o= 0.56 (s, 6H, (CH3)2Si), 0.70 (s, 6H, (CH3)2Si), 0.99 (d, 6H, (CH3)2CH, J = 6.9), 1.78 (m, -0.8H, protio THF), 1.97 (d, 12H, (CH3)2CH, J = 6.8), 2.83 (m, lH, (CH3)2CH, J = 6.86), 2.89 (m, 2H, (CH3)2CH, J = 6.79), 5.75 (s, 1H, Cp-H), 3.62 (m, -0.8H, protio THF), 6.26 (s, 2H, Cp-H). 13H NMR (THF-ds): o= 5.19, 9.72 ((CH3)2Si), 27.22, 34.83 ((CH3)2CH, (CH3)2CH, overlapping peaks), 112.08, 121.57, 126.40, 139.89, 158.64 (Cp). Removal of protio THF from 7. Tetrahydrofuran was removed from 7 with an analogous procedure to that used for 5. In the glove box, 7 (0.35 g) was placed in a 50 mL round bottom flask and the Soxhlet apparatus was assembled as for 5. Toluene (30 mL) was added to the round bottom flask and the Soxhlet extraction was carried out for 30 hr. The flask was attached to a fine porosity swivel frit assembly, toluene was removed and hexane (20 mL) was added via vacuum transfer to provide a white slurry. A white solid was filtered away from a yellow supernatant; the product was washed with recycled hexane (2 x 10 mL) and dried 52 under high vacuum for 12 hr; 0.49 g. lH NMR (THF-ds): same chemical shifts as 7 but no protio THF present. [(1,2-SiMe2h(115-4-CMe3-CsH2)(115-3,5-(CHMe2h-CsH)]YI(THF) (tBuThpYI(THF), 8a), {[(1,2-SiMe2h(115-4-CMe3-CsH2)(115-3,5-(CHMe2hCsH)]Y(~-t-l)h {[tBuThpY(~-t-nh, 8b} In the glove box, a 100 mL round bottom flask equipped with stir bar was charged with 5 (678 mg, 1.13 mmol) and Nal (381 mg, 2.54 mmol, 2.2 equiv) and a fine swivel frit assembly attached. On the vacuum line, tetrahydrofuran (50 mL) was added by vacuum transfer while stirring at -78°C, and then this cold bath was replaced by a ooc ice water bath and the reaction was allowed to slowly warm to 25°C. After 48 hr of reaction at 25°C, solvent was removed in vacuo, petroleum ether (20 mL) was added by vacuum transfer, and the resulting slurry was stirred for 30 minutes. The solvent was removed in vacuo and the solid dried under high vacuum for 4 hr. Diethyl ether (25 mL) was added by vacuum transfer to provide a yellow slurry; this slurry was stirred for 12 hr. A yellow-orange solution was filtered away from a white solid and the solid washed with recycled solvent (3 x 15 mL). Solvent was removed in vacuo and pentane (25 mL) was added to the collection flask via vacuum transfer. An orange solution was filtered away from a white solid, solvent was removed in vacuo, and this white solid was dried under high vacuum for 4 hr. 8a/8b was isolated as a white solid; 470 mg (44.5%). 8a: lH NMR (THFds): 8 = 0.55 (s, 6H, (CH3)2Si), 0.66 (s, 3H, (CH3)2Si), 0.70 (s, 3H, (CH3)2Si), 0.99 (d, 3H, (CH3)2CH, J = 7.0), 1.20 (d, 3H, (CH3)2CH, J = 6.6), 1.23 (d, 3H, (CH3)2CH), 1.33 (s, 9H, (CH3)3C), 1.39 (d, 3H, (CH3)2CH), 1.78 (m, 4H, protio THF), 2.97 (m, 1H, (CH3)2CH, J = 5.6), 3.05 (m, 1H, (CH3)2CH, J = 5.6), 3.62 (m, 4H, protio THF), 5.98 (s, 1H, Cp-H), 6.46 (s, 1H, Cp-H), 6.52 (s, 1H, Cp-H). 8b: 1 H NMR (THF-ds): 8 = 0.54 (s, 6H, (CH3)2Si), 0.70 (s, 6H, (CH3)2Si), 0.98 (d, 6H, (CH3)2CH, J = 7.0), 1.20 (d, 6H, (CH3)2CH, J = 6.6), 1.27 (s, 9H, (CH3)3C), 2.83 (m, 2H, (CH3)2CH, J = 6.8), 5.86 (s, 1H, Cp-H), 6.30 (s, 2H, Cp-H). [(1,2-SiMe2)2(115-4-CHMe2-CsH2)(115-3,5-(CHMe2h-CsH)]Sc(~-t-Br)2K(THF)n (iPrThpSc(~-t-BrhK(THF)n, 9). In the glove box, a 100 mL round bottom flask equipped with stir bar was charged with 4 (971 mg, 2.17 mmol), ScCl3(THF)3 (798 mg, 1 equiv), and NaBr (849 m g, 8.25 mmol, 3.8 equiv) and a 14/20 reflux conden sor and 180° needle valve attached. On the vacuum line, tetrahydrofuran (30 mL) was added by vacuum transfer and the reaction mixture was heated to 53 reflux under an argon atmosphere. After 4 hr of reaction, solvent was removed in vacuo and the solid was dried under high vacuum for 2 hr. In the glove box, a medium swivel frit assembly was attached. Petroleum ether (30 mL) was added by vacuum transfer, and the resulting yellow-white slurry was stirred for 12 hr. Solvent was removed in vacuo and diethyl ether (25 mL) was added by vacuum transfer to provide a yellow slurry. This slurry was stirred for 3 hr, and then a yellow solution was filtered away from a white solid. The solid was washed with recycled solvent (5 x 15 mL) and then solvent was removed in vacuo to provide a pale yellow foam in the collection flask. Petroleum ether (25 mL) was added to the collection flask via vacuum transfer, the slurry was stirred for 1 hr, and then solvent was removed in vacuo. The resulting pale yellow solid was dried under high v acuum for 12 hr. 9 was isolated as a pale yellow solid; 898 m g (65.7%). lH NMR (THF-ds): () = 0.54 (s, 6H, (CH3)2Si), 0.70 (s, 6H, (CH3)2Si), 0.98 (d, 6H, (CH3)2CH, J = 6.9), 1.20 (d, 6H, (CH3)2CH, J = 6.6), 1.21 (d, 6H, (CH3)2CH, J = 6.9), 1.78 (m, -O.SH, protio THF), 2.84 (m, 1H, (CH3)2CH, overlapping), 2.85 (m, 2H, (CH3)2CH, overlapping), 3.62 (m, - O.SH, protio THF), 5.82 (s, 1H, Cp-H), 6.21 (s, 2H, Cp-H). [(1,2-SiMe2h (TJS-4-CMe3-CsH2) (TJ 5-3,5-( CHMe2h-CsH) ]YCH (SiMe3h (10). (tBuThpYCH(TMSh). In the g love box, a 100 mL flask was charged with 8a/8b (422 m g, 0.70 mmol) and KCH(TMS)2 (154 mg, 1.1 equiv) and a fine swivel frit assembly was attached. On the vacuum line, toluene (50 mL) was added by vacuum transfer while stirring at -78°C, and then this cold bath was replaced by a 0°C ice water bath and the reaction was allowed to slowly warm to 25°C w hile stirring. After 23 hr of reaction, a yellow solution was filtered away from an offw hite solid and the solid w as washed with recycled solvent (3 x 25 mL). Toluene was rem oved in vacuo and then pentane was added by vacuum tran sfer (10 mL). After stirring for 6 hr, pentane was removed in vacuo and then added again (20 mL). This pentane slurry was stirred for 12 hr, and then a pale yellow solution was filtered away from an off-white solid. Solvent was removed in vacuo and the apparatus was left open to d ynamic vacuum for 4 hr. In the dry box, the offwhite powder (from the collection flask) was collected as a first crop of the desired product. A new collection flask was attached to the swivel frit assembly in order to collect a second crop of the d esired p roduct. The extraction procedure was repeated w ith toluene and pentane as described, but the final filtration was carried out at -78°C to maximize the product yield. Two crops of 54 an off-white powder were collected; 211 mg (47.8%). Major isomer lH NMR (benzene-d6): 8 = -0.19 (s, 1H, CH(Si(CH3)3)2), 0.14 (s, 18H, CH(Si(CH3)3)2), 0.48 (s, 6H, (CH3)2Si), 0.89 (s, 6H, (CH3)2Si), 1.06 (d, 6H, (CH3)2CH, J = 6.8), 1.28 (d, 6H, (CH3)2CH, J = 6.7), 1.35 (s, 9H, (CH3)3C), 2.70 (m, 2H, (CH3)2CH, J = 6.7), 6.40 (s, 1H, Cp-H), 6.42 (s, 2H, Cp-H). Minor isomer lH NMR (benzene-d6): 8 = -0.18 (s, 1H, CH(Si(CH3)3)2), 0.15 (s, 18H, CH(Si(CH3)3)2), 0.50 (s, 6H, (CH3)2Si), 0.89 (s, 6H, (CH3)2Si), 1.08 (d, 6H, (CH3)2CH, J = 6.4), 1.28 (d, 6H, (CH3)2CH, J = 6.7), 1.35 (s, 9H, (CH3)3C), 2.74 (m, 2H, (CH3)2CH, J = 6.7), 6.21 (s, 1H, Cp-H), 6.34 (s, 2H, Cp-H). Major and minor isomers 13H NMR (benzene-d6): 8 = 0.05, 1.78, 3.76, 3.95, 4.08, 4.11, 4.42, 4.61 ((CH3)2Si, CH(Si(CH3)3)2), 21.81, 22.13, 24.63, 24.88, 29.17, 29.26, 29.78, 29.85, 30.58, 31.92, 32.20, 32.58, 33.05, 33.33 ((CH3)2CH, (CH3)3C), 109.02, 110.68, 119.79, 120.85, 124.38, 125.16, 125.33, 125.55, 144.76, 145.93, 154.61, 154.78 (Cp). {[(1,2-SiMez)z(115-4-CMe3-CsHz)(115-3,5-(CHMez)z-CsH) ]YH }z (lla/llb ). ((tBuThp YH)z). In the glove box, a thick walled reaction vessel equipped with stir bar was charged with 10 (57 mg, 0.90 mmol) and benzene (2 mL). The apparatus was degassed on the vacuum line using two freeze-pump-thaw cycles. The vessel was cooled to -78°C and dihydrogen was admitted. After 5 minutes of exposure to dihydrogen, the Kontes valve of the vessel was closed and the reaction was warmed to 25°C with vigorous stirrl.ng. After 20 hr of reaction, the pale yellow solution was frozen and the benzene was removed by lyophiliz ation. The resulting pale yellow powder was dissolved in toluene-ds and cooled slowly to encourage growth of X-ray quality crystals. As a consequence a product yield was not determined. Major product (llb) lH NMR (benzene-d6): 8 = 0.52 (s, 6H, (CH3)2Si), 0.54 (s, 6H, (CH3)2Si), 1.18 (d, 6H, (CH3)2CH, J = 6.7), 1.38 (d, 6H, (CH3)2CH, J = 6.7), 1.46 (s, 9H, (CH3)3C), 2.78 (t, 2H, Y-(~-H), J = 32.0), 2.86 (m, 2H, (CH 3)2CH, J = 6.7), 6.10 (s, 2H, Cp-H), 6.76 (s, 1H, Cp-H). 13H NMR (tolueneds): 8 = 2.09, 5.77 ((CH3)2Si), 23.74, 25.58, 29.65, 30.31, 33.53 ((CH3)2CH, (CH 3)3C), 107.71, 116.47, 123.05, 126.21, 143.53, 147.89 (Cp). Minor product (lla) lH NMR (benzene-d6): 8 = 0.49 (s, 6H, (CH3)2Si), 0.58 (s, 6H, (CH3)2Si), 1.07 (d, 6H, (CH3)2CH, J = 7.0), 1.24 (d, 6H, (CH3)2CH, J = 6.9), 1.54 (s, 9H, (CH3)3C), 2.51 (t, 2H, Y-(~-H), J = 31.5), 2.84 (m, 2H, (CH3)2CH), 6.19 (s, 2H, Cp-H), 6.59 (s, 1H, CpH). 13H NMR (toluene-ds): 8 = 4.29, 6.13 ((CH3)2Si), 23.12, 27.78, 28.89, 33.10, 33.37 ((CH3)2CH, (CH3)3C), 109.00, 112.58, 126.00, 127.08, 144.32, 153.75 (Cp). 55 [(1,2-SiMe2h(T\5-4-CMe3-CsH2)(T\5-3,5-(CHMe2h-CsH)]Y(j.i-(CH3)hAl(CH3)2 (12). (tBuThpYMe2AlMe2). In the dry box a 100 mL round bottom flask equipped with stir bar was charged with 5 (501 m g, 0.83 mmol) and LiA1Me4 (149 mg, 1.58 mmol, 1.9 equiv) and a fine swivel frit assembly was attached. On the vacuum line, toluene (75 mL) was added to the flask b y vacuum transfer, and the dry ice/ acetone bath was left intact to allow the reaction to slowly warm to 25°C while stirring. After 24 hr of reaction, toluene was removed in vacuo and pentane (40 mL) was added by vacuum transfer. The pale yellow slurry was stirred for 12 hr, and then a pale yellow solution was filtered away from a white solid. The solid was washed with recyled pentane (10 x 20 mL) and the pentane was removed in vacuo to provide an off-white residue in the collection flask that was dried under high vacuum for 4 hr. Complex 12 was isolated as an off-white powder; 322 mg (58.9%). lH NMR (benzene-d6): 5 = -0.41 (s, 3H, (1-1CH3)2Al(CH3)2), -0.33 (s, 3H, (j.i-CH3)2Al(CH3)2), -0.32 (s, 6H , (j.i-CH3)2Al(CH3)2), 0.40 (s, 6H, (CH3)2Si), 0.87 (s, 6H, (CH3)2Si), 1.03 (d, 6H, (CH3)2CH, J = 6.8), 1.23 (d, 6H, (CH3)2CH, J = 6.7), 1.27 (s, 9H, (CH3)3C), 2.63 (m, 2H, (CH 3)2CH, J = 6.7), 6.32 (s, 1H, Cp-H), 6.33 (s, 2H, Cp-H). 13H NMR (toluene-ds): 5 = -0.41, 3.45 ((CH3)2Si), 20.96, 29.04, 29.35, 32.08, 32.53 ((CH3)2CH, (CH3)3C), 109.91, 124.01, 125.22, 143.40, 154.95, 158.19 (Cp). (j.i-CH3)2Al(CH3)2 resonan ces not located. [(1,2-SiMe2h(T\5-4-CMe3-CsH2)(T\5-3,5-(CHMe2)2-CsH)]Sc(j.i-(CH3))2Al(CH3)2 (13). (tBuThpScMe2AlMe2). In the dry box a 100 mL round bottom flask equipped with stir bar was charged with 6 (297 m g, 0.39 mmol) and LiAlMe4 (369 mg, 3.72 mmol, 3.5 equiv) and a fine swivel frit assembly was attached. On the vacuum line, toluene (50 mL) was added to the flas k b y vacuum transfer, and the dry ice/acetone bath was removed to allow the reaction to slow ly warm to 25°C while stirring. After 24 h r of reaction, toluene was removed in vacuo and pentane (40 mL) was added by vacuum transfer. The p ale yellow slurry was stirred for 12 hr, and then a yellow solution was filtered away from a white solid. The solid was washed with recyled pentane (5 x 20 mL) and the pentane was removed in vacuo to provide a yellow solid that was dried under high vacuum for 4 hr. In the dry box, this yellow solid was dissolved in benzene (2.5 mL) and transferred to a 10 mL round bottom flask equipped with stir bar. A 180° needle valve was attached . On the vacuum line, the solution was frozen and the benzene lyophilized away in vacuo. Complex 13 was isolated as a pale tan powder; 215 mg (78.6%). lH NMR (benzene-d6): 5 = -0.38 (s, 3H , (j.i- 56 CH3)2Al(CH3)2), -0.35 (s, 6H, (~-CH3)2Al(CH3)2), -0.23 (s, 3H, (~-CH3)2Al(CH3)z), 0.39 (s, 6H, (CH3)2Si), 0.81 (s, 6H, (CH3)2Si), 0.99 (d, 6H, (CH3)2CH, J = 6.8), 1.24 (d, 6H, (CH3)2CH, J = 6.6), 1.31 (s, 9H, (CH3)3C), 2.55 (m, 2H, (CH3)2CH, J = 6.7), 6.24 (s, 2H, Cp-H), 6.49 (s, 1H, Cp-H). 13H NMR (toluene-ds): () = -6.28, -4.38 ((~­ CH3)2Al(CH3)2, broad singlets), -0.92, 3.52 ((CH3)2Si), 30.27 ((~-CH 3 )2Al(CH3 )2), 20.83, 29.07, 29.14, 31.49, 33.26 ((CH3)2CH, (CH3)3C), 113.55, 116.14, 121.05, 126.67, 137.37, 155.87 (Cp ). [(1,2-SiMezh(1l5-4-CHMez-CsHz)(1l5-3,5-(CHMez)z-CsH)]Sc(~-(CH3)z)Al(CH 3 h (14). (iPrThpScMezAIMez). In the dry box a 100 mL round bottom flask equipped with stir bar was charged with 9 (606 mg, 0 .97 mmol) and LiA1Me4 (369 mg, 3.72 mmol, 3.8 equiv) and a fine swivel frit assembly was attached. On the vacuum line, toluene (50 mL) was added to the flask by vacuum transfer, and the dry ice/acetone bath was removed to allow the reaction to slowly warm to 25°C while stirring. After 28 hr of reaction, toluene was removed in vacuo and pentane (40 mL) was added by vacuum transfer. The pale yellow slurry was stirred for 12 hr, and then a yellow-orange solution was filtered away from a white solid. The solid was washed with recyled pentane (5 x 20 mL) and the pentane was removed in vacuo to provide a yellow solid that was dried under high vacuum for 4 hr. In the dry box, this yellow solid was dissolved in benzene (2.5 mL) and transferred to a 10 mL round bottom flask equipped with stir bar. A 180° needle valve was attached. On the vacuum line, the solution was frozen and the benzene lyophilized away in vacuo. Complex 14 was isolated as a pale yellow solid; 407 mg (83.8%). lH NMR (benzene-d6): () = -0.45 (s, 3H, (~­ CH3)2Al(CH3)2), -0.44 (s, 6H, (~-CH3)2Al(CH3)2), -0.25 (s, 3H, (~-CH3)2Al(CH3)2), 0.36 (s, 6H, (CH3)2Si), 0.81 (s, 6H, (CH3)2Si), 0.97 (d, 6H, (CH3)2CH, J = 6.8), 1.20 (d, 6H, (CH3)2CH, J = 6.7), 1.21 (d, 6H, (CH3)2CH, J = 6.4), 2.53 (m, 2H, (CH3)2CH, J = 6.7), 3.03 (m, 1H, (CH3)2CH, J = 6.6), 6.06 (s, 2H, Cp-H), 6.43 (s, 1H, Cp-H). 13H NMR (toluene-ds): () = -0.94, 3.51 ((CH3)2Si), 24.12, 27.58, 29.11 ((CH3)2CH), 112.31, 116.27, 120.99, 134.40, 139.15, 155.70 (Cp). (~-CH3)2Al(CH3)2 resonances not located. [{(C6Hs)zC[(1l5-CsH4)(1l5-Ct3Hs)]}YCl]z (15). ([EpYCl]z). In the dry box a 100 mL round bottom flask equipped with stir bar was charged with LizEp (2.01 g, 4.94 mmol) and YCl3(THFhs (2.21 g, 1 equiv) and a fine swivel frit assembly was attached. On the vacuum line, tetrahydrofuran (50 mL) was added to the flask 57 by vacuum transfer, and the dry ice/ acetone bath was removed to allow the reaction to slowly warm to 25°C while stirring. The reaction mixture begins as cherry-red solution and slowly changes to brick-red in color. After 72 hr of reaction, tetrahydrofuran was removed in vacuo and petroleum ether (50 mL) was added by vacuum transfer. The slurry was stirred for 12 hr and then solvent was removed in vacuo. Diethyl ether (50 mL) was added by vacuum transfer and subsequent filtration provided a bright yellow solution in the collection flask. The solid was washed with recycled solvent (18 x 30 mL) until the solid remaining on the frit was no longer yellow in color. Solvent was removed in vacuo to leave a bright yellow solid in the collection flask. In the dry box, the collection flask was attached to a fine swivel frit assembly. Petroleum e ther (40 mL) was added via vacuum transfer, and a yellow solution was filtered away from a bright yellow solid. The solid was washed with recycled solvent (5 x 20 mL), solvent was removed in vacuo, and the b right yellow solid that was dried under high vacuum for 4 hr. Complex 15 was isolated as an bright yellow powder; 2.27 g; (44.5%). lH NMR (THF-ds): o= 5.82 (s, 2H, Cp-H), 5.91 (s, 2H, Cp-H), 6.57 (d, 2H, Flu-H, J = 8.7), 6.78 (t, 2H, Ph-H, J = 7.7), 6.94 (t, 2H, Ph-H, J = 7.2), 7.09 (t, 2H, Flu-H, J = 7.2), 7.13 (t, 2H, Flu-H, J = 7.5), 7.27 (t, 2H, Ph-H, J = 8.0), 7.87 (d, 2H, Ph-H, J = 7.4), 8.03 (d, 2H, Flu-H, J = 8.3), 8.06 (d, 2H, Ph-H, J = 7.4). [{(C6HshC[(TJS-CsH4)(TJS-C13Hs)]}ScCl(THF) (16). (EpScCl(THF)). In the dry box a 100 mL round bottom flask equipped with stir bar was charged with Li2Ep (3.00 g, 7.37 mmol) and ScCb(THF)3 (2.71 g, 1 equiv) and a fine swivel frit assembly was attached. On the vacuum line, tetrahydrofuran (75 mL) was added to the flask by vacuum transfer, and the dry ice/ acetone bath was removed to allow the reaction to slowly warm to 25°C while stirring. The reaction mixture begins as red-brown slurry and slowly changes to a red-orange transparent solution. After 96 hr of reaction, tetrahydrofuran was removed in vacuo and petroleum ether (50 mL) was added by vacuum transfer. The slurry was stirred for 9 hr and then solvent was removed in vacuo. The solid was dried under high vacuum for 12 hr. Next, diethyl ether (50 mL) was added by vacuum transfer to provide a bright orange slurry. An orange solution was filtered from a redorange solid, and this solid was washed with recycled solvent (8x 30 mL) until the solid remaining on the frit was no longer orange in color. Solvent was removed in vacuo to leave an orange-yellow solid in the collection flask. In the dry box, 58 the collection flask was attached to a new fine swivel frit assembly. Diethyl ether (40 mL) was added via vacuum transfer and then the swivel frit assembly was cooled to -78°C for a cold filtration. A red-orange solution was filtered away from a bright yellow solid. The solid was washed with recycled solvent at -78°C (1 x 20 mL) and then solvent was removed in vacuo. Petroleum ether (30 mL) was added by vacuum transfer and the bright yellow solid was washed with recycled solvent (4 x 20 mL). The solvent was removed in vacuo and then the solid was dried under high vacuum for 4 hr. Complex 16 was isolated as an bright yellow powder; 1.01 g (24.9%). lH NMR (THF-ds): o = 1.78 (m, 4H, protio THF), 3.62 (m, 4H, protio THF), 5.75 (s, 2H, Cp-H), 5.87 (s, 2H, Cp-H), 6.45 (d, 2H, Flu-H, J = 8.7), 6.71 (t, 2H, Ph-H, J = 7.3), 7.00 (t, 2H, Ph-H, J = 7.5), 7.13 (t, 2H, FluH , J = 6.2), 7.18 (t, 2H, Flu-H, J = 7.2), 7.31 (t, 2H, Ph-H, J = 6.9), 7.88 (d, 2H, Ph-H, J = 6.3), 7.90 (d, 2H, Ph-H, J = 7.7), 8.06 (d, 2H, Ph-H, J = 7.6). {(C6HshC[(llS-CsH4)(115-Ct3Hs)]}Y(j.!-(CH3h)Al(CH3h (17). (EpYMezA1Me 2 ). In the dry box a 100 mL round bottom flask equipped with stir bar was char ged with 15 (511 mg, 0.492 mmol) and LiAlMe4 (162 mg, 1.72 mmol, 3.5 equiv) and a fine swivel frit assembly was attached . On the vacuum line, toluene (50 mL) was added to the flask by vacuum transfer, and the dry ice/acetone bath was removed to allow the reaction to slowly warm to 25°C while stirring. After 21.5 hr of reaction, toluene was removed in vacuo and petroleum ether (50 mL) was added by vacuum transfer. The slurry was stirred for 1 hr and then solvent was removed in vacuo. In the dry box, the contents of the reaction flask were transferred to a small Soxhlet thimble, and a Soxhlet apparatus was assembled with a small Soxhlet extractor, 14/20 condensor, 180° needle valve, and 25 mL collection flask. On the vacuum line, pentane (15 mL) was added by vacuum transfer, the apparatus was backfilled with argon, and the toluene solution was heated to reflux to begin the extraction. After 8 hr, the solution that passed through the thimble was colorless and the extraction was terminated. Pentane was removed in vacuo to provide a bright yellow solid that was dried under high vacuum for 4 hr. Complex 17 was isolated as an bright yellow powder; 44 mg (7.8%). lH NMR (benzene-d6): o = -1.22 (s, 12H, (j..l-CH3)2Al(CH3)2, broad), 5.74 (s, 2H, Cp-H), 5.78 (s, 2H, Cp-H), 6.60 (d, 2H, Flu-H, J = 8.6), 6.75 (t, 2H, Ph-H, J = 7.4), 6.96 (t, 2H, Ph-H, J = 7.4), 7.00 (t, 2H, Flu-H, J = 7.3), 7.03 (t, 2H, Flu-H, J = 6.8), 7.15 (t, 2H, Ph-H, J = 7.5), 7.75 (d, 2H, Flu-H, J = 7.8), 7.94 (d, 2H, Ph-H, J = 7.4), 8.01 (d, 2H, Ph-H, J = 8.2). 13C NMR (benzene-d6): o= 30.58, 37.31, 60.30, 59 90.68, 106.24, 112.83, 120.09, 120.67, 121.16, 121.63, 123.96, 125.84, 126.77, 126.94, 127.90, 129.09, 129.30, 130.28, 147.75. {(C6Hs)zC[(Tl5-CsH4)(Tl5-C13Hs)]}Sc(!J.-(CH3)z)Al(CH3)z (18). (EpScMezAIMez). In the dry box a 100 mL round bottom flask equipped with stir bar was charged with 16 (492 mg, 0.90 mmol) and LiAlMe4 (296 mg, 3.15 mmol, 3.5 equiv) and a fine swivel frit assembly was attached. On the vacuum line, toluene (50 mL) was added to the flask by vacuum transfer, and the dry ice / acetone bath was removed to allow the reaction to slowly warm to 25°C while stirring. After 8 hr of reaction, toluene was removed in vacuo and pentane (40 mL) was added by vacuum transfer. The reaction mixture was stirred for 12 hr and then solvent was removed in vacuo. In the dry box, the contents of the reaction flask were transferred to a small Soxhlet thimble, and a Soxhlet apparatus was assembled with a small Soxhlet extractor, 14/20 condensor, 180° needle valve, and 25 mL collection flask. On the vacuum line, pentane (15 mL) was added by vacuum transfer, the apparatus was backfilled with argon, and the toluene solution was heated to reflux to begin the extraction. The extraction was terminated after 6 hr. Pentane was removed in vacuo to provide an orange powder that was dried under high vacuum for 4 hr. Complex 18 was isolated as an bright orange solid; 57 mg (12.1 %). lH NMR (benzene-d6): () = -1.83 (s, 6H, (~-t-CH3)2Al(CH3)2), -0.55 (s, 3H, (~-t-CH3)2Al(CH3)2), -0.52 (s, 3H, (1J.-CH3)2Al(CH3)2), 5.46 (s, 2H, Cp-H), 5.78 (s, 2H, Cp-H), 6.50 (d, 2H, Flu-H, J = 8.8), 6.59 (t, 2H, Ph-H, J = 6.9), 6.97 (t, 2H, Ph-H, J = 7.4), 7.03 (t, 2H, Flu-H, J = 7.4), 7.06 (t, 2H, Flu-H, J = 8.6), 7.15 (t, 2H, Ph-H, J = 7.7), 7.77 (d, 2H, Flu-H, J = 7.9), 7.89 (d, 2H, Ph-H, J = 8.1), 7.91 (d, 2H, Ph-H, J = 6.0). 13C NMR (benzene-d6): () = 10.27, 25.15, 30.59, 60.58, 70.41, 87.76, 106.27, 116.16, 117.12, 121.71, 122.43, 123.38, 123.80, 123.93, 126.18, 127.06, 127.73, 129.18, 129.35, 130.40, 147.29. Polymerizations of 1-pentene using 12, 13, 14, 18, and 10 +Hz as catalysts. 1- pentene polymerizations were executed in neat monomer; this reagent was stored under vacuum over lithium aluminum hydride and freshly distilled immediately prior to use. Approximately 5 mg ("" 0.010 mmol) of metallocene and 5000 equivalents of 1-pentene were used for each polymerization. The specific conditions for these polymerizations, such as temperature, duration, and percent yield (by mass), as well as pentad information40 are given in Table 6. Measurements of polymer molecular weight were made elsewhere. 41 60 Representative polymerization: In the dry box a thick walled reaction vessel equipped with stir bar was charged with 18 (5.4 mg, 0.010 mmol). The vessel was cooled to -78°C and 1-pentene (5.6 mL, 5000 equiv) was added by vacuum transfer. The reaction was warmed to 21oc with vigorous stirring. After 24 hr of reaction, the solution was slightly viscous. In the fume hood, the reaction solution was rinsed into a flask with diethyl ether (10 mL). While stirring rapidly, methanol (6 mL), dilute methanol-HCl (6 mL, 3 :1, v /v), and additional methanol (50 mL) were added to quench the reaction. A white semi-solid precipitates out this solution; it was removed and dried in vacuo at 50°C for 4 hr. The product was obtained in 49.9% yield by mass (1.79 g). A small sample was dissolved in 1,2-dichlorobenzene-benzene-d6 (9 : 7, v /v) and analyzed by 13C NMR spectroscopy at 323 K to determine the polymer pentad distribution. Polymerizations of propylene using 12, 13, 14, and 18 as catalysts. Most propylene polymerizations were carried out in neat monomer at -5°C in a thick walled glass vessel. A 5 mm Kontes needle valve with an extended tip was used to seal the vessel. Approximately 10 mg ("" 0.020 mmol) of metallocene and 4 mL of propylene (at 77 K) ("" 3000 equiv) were used for each polymerization. Propylene was stored under vacuum over triisobutylaluminum ("" 1:1 v / vat 77 K) and distilled immediately prior to use. Monomer was first distilled into a calibrated trap for volume measurement and then distilled into the liquid nitrogen cooled reaction vessel. The reaction mixture was warmed to -5°C with rapid stirring in a sodium chloride/ice water cold bath. Multiple blast shields were used as a precaution due to the elevated pressure in the reaction vessel. Two polymerizations were carried out using a 50/50 (v /v) mixture of propylene and toluene; these experiments were run to evaluate the effect of monomer concentration on polymer tacticity. The pentad distributions42 for these polymerizations are provided in Table 7. Measurements of polymer molecular weight were made elsewhere.41 Representative polymerization: In the dry box a thick walled reaction vessel equipped with stir bar was charged with 18 (6.6 mg, 0.0125 mmol). The vessel was cooled to with liquid nitrogen and propylene (3.1 mL at 77 K, ""3100 equiv) was added by vacuum transfer. In the fume hood behind multiple blast shields, the reaction was warmed to -5°C in a sodium chloride/ice water cold bath with v igorous stirring. After 10.67 hr of reaction, the solution was slightly viscous. The reaction was slowly vented to release excess propylene. The reaction 61 contents were dissolved in a minimal amount of diethyl ether (10 mL) and transferred to a flask. While stirring rapidly, methanol (10 mL), dilute methanolHCl (10 mL. 3 :1, v /v), and additional methanol (50 mL) were added to quench the reaction. A white semi-solid precipitates out this solution; it was removed and dried in vacuo at 50°C for 4 hr. The product was obtained in 44.7% yield by mass (0.72 g). A small sample was dissolved in 1,2-dichlorobenzene-benzene-d6 (9: 7, v /v) and analyzed by 13C NMR spectroscopy at 323 K to determine the polymer pentad distribution. References 1. Brintzinger, H .H.; Fischer, D.; MUlhaupt, R.; Rieger, B.; Waymouth, R.M. Angew. Chern. Int. Ed. Engl. 1995, 34, 1143. 2. Ewen, J.A.; Jones, R.L.; Razavi, A .; Ferrara, J.D. f. Am. Chern. Soc., 1988, 110, 6255. 3. (a) Patsidis, K.; Alt, H . G .; Milius, W .; Palackal, S. J. J. Organomet. Chern. 1996, 509,63. (b) Razavi, A .; Atwood, J. L. J. Organomet. Chern. 1993,459, 117. (c) Winter, J.; Rohrmann, M.; Dolle, V.; Spaleck, W. Eur. Pat. Appl. 0,387,690 and 0,387,691, 1991. (d) Spaleck, W.; Aulbach, M.; Bachmann, B.; Kuber, F.; Winter, A . Macromol. Symp. 1995,89,237. (e) Ewen, J. A. Macromol. Symp. 1995, 89, 181. (f) Alt, H. G.; Zenk, R. J. Organomet. Chern . 1996, 518, 7. 4. Herzog, T.A.; Zubris, D.L.; Bercaw, J.E. f. Am. Chern. Soc., 1996, 118, 11988. 5. (a) Longo, P .; Grassi, A.; Pellecchia, C.; Zambelli, A . Macromolecules 1987, 20, 1015-1018. (b) Pino, P.; Galimberti, M. f. Organomet. Chem. 1989, 370, 1. 6. Gilchrist, J. H.; Bercaw, J. E. f. Am. Chern. Soc. 1996, 118, 12021. 7. (a) Piers. W.E.; Bercaw, J.E. f. Am. Chern. Soc. 1990, 112,9406. (b) Grubbs, R.H.; Coates, G .W. Ace. Chem . Res. 1996, 29, 85. 8. Veghini, D.; Henling, L.M.; Burkhardt, T.J.; Bercaw, J.E. f. Am. Chem. Soc., 1999, 121 , 564. 9. Bierwagen, E.P .; Bercaw, J.E.; Goddard, W .A . f. Am. Chern. Soc., 1994, 116, 1481. 10. Bunel, E. E. Ph.D. Thesis, California Institute of Technology, 1989. 11. (a) Chirik, P .J.; Bercaw, J.E . in M etallocenes: Synthesis, Reactivity, Applications, Vol. 1; Togni, A .; Halterman, R.L. Eds.; Wiley-VCH: Weinheim, Germany, 1998, pp. 111-152. (b) Schumann, H.; Meese-Marktscheffel, J.A.; Esser, L. Chern. Rev. 1995, 95, 865. 62 12. (a) Henling, L.M.; Herzog, T.A.; Bercaw, J.E. Acta Crys tallogr., Sect. C 52, 1996, submitted. (b) Veghini, D.; Day, M.W.; Bercaw, J.E. Inorganica Chimica Acta 1998, 280, 226. 13. Coughlin, E.B. Ph.D. Thesis, California Institute of Technology, 1994. 14. Evans, W .J.; Peterson, T.T.; Rausch, M .D .; Hunter, W.E.; Zhang, H.; Atwood, J.L. Organometallics 1985, 4, 554. 15. Evans, W.J.; Olofson, J.M.; Zhang, H.; Atwood, J.L. Organometallics 1988, 7, 629. 16. Xie, Z.; Liu, Z .; Zhang, Z.; Mak, T.C. W . f. Organomet. Chern . 1997, 542, 285. 17. Coughlin, E.B.; Henling, L.M.; Bercaw, J.E. Inorg. Chimica Acta 1996, 242, 205. 18. Stern, D.; Sabat, M .; Marks, T.J. f. Am. Chern. Soc. 1990, 112, 9558. 19. Schaverien, C.L. Adv. Organometallic. Chem. 1994, 36, 283. 20. Abrams, M.A. Ph.D. Thesis California Institute of Technology, 1998. 21. Coughlin, E. B. Ph.D. Thesis California Institute of Technology, 1994. 22. Mitchell, J.P.; Hajela, S.; Brookhart, S.K.; Hardcastle, K.I.; H enling, L.M.; Bercaw, J.E. f. Am. Chem. Soc. 1996, 118, 1045. 23. (a) Ballard, D.G.H .; Pearce, R. J.C.S . Chem. Comm. 1975,621 . (b) Holton, J.; Lappert, M.F.; Scollary, G.R.; Ballard, D .G.H.; Pearce, R.; Atwood, J.L.; Hunter, W.E. J. C.S. Chem. Comm. 1976, 12, 425. (c) Holton, J.; Lappert, M.F.; Ballard, D.G.H .; Pearce, R.; Atwood, J.L.; Hunter, W .E. J.C. S. Dalton. 1979, 45. (d) Holton, J.; Lappert, M.F.; Ballard, D .G.H.; Pearce, R.; Atwood, J.L.; Hunter, W.E. J.C.S. Dalton. 1979, 54. 24. Evan s, W .J.; Chamberlain, L.R.; Ulibarri, T.A.; Ziller, J.W. f. Am. Chem. Soc. 1988, 110, 6432. 25. (a) Watson, P .L. f. Am. Chem. Soc. 1982, 104,337. (b) Watson, P.L.; Parshall, G.W. Ace. Chern. Res. 1985, 18, 51. (c) Busch, M.A.; Harlow, R.; Watson, P.L. Inorganica Chimica Acta 1987, 140, 15. 26. den Haan, K.H.; Wielstra, Y.; Eshuis, J.J.W.; Teuben, J.H. f. Organomet. Chern. 1987, 323, 181. 27. Holton, J.; Lappert, M.F.; Ballard, D.G.H.; Pearce, R.; Atwood, J.L.; Hunter, W.E. J. C.S. Dalton. 1979, 54. 28. Strauss, D.A.; Grubbs, R.H . f. Mol. Cat. 1985, 28, 9. 63 29. Razavi, A.; Atwood, J.L. J. Organomet. Chem. 1993, 459, 117. 30. Schofer, S.J.; Bercaw, J.E. unpublished results. 31. Coughlin, E.B.; Bercaw, J.E. J. Am. Chem. Soc. 1992, 114, 7606. 32. Piers, W.E.; Shapiro, P.J.; Bunel, E.E.; Bercaw, J.E. Synlett, 1990, 2, 74. 33. Burger, B. J.; Bercaw, J. E. New Developments in the Synthesis, Manipulation, and Characterization of Organometallic Compounds, 1987; Vol. 357. ACS Symposium Series. 34. Marvich, R. H.; Brintzinger, H. H . J. Am. Chem . Soc. 1971, 93, 203. 35. Cowley, A. H.; Kemp, R. A. Synth . React. Inorg. Metal-Org. Chem. 1981, 11, 591. 36. Manzer, L.E. Inorg. Synth. 1982, 21, 135. 37. Herzog, T.A. Ph.D. Thesis, California Institute of Technology, 1997. 38. Perrin, D. D.; Armagrego, W . L. F. Purification of Laboratory Chemicals, 3rd ed.; Pergamon Press: New York, NY, 1988. 39. H erzog, T.A.; Bercaw, J.E. unpublished results. 40. Asakura, T.; Demura, M.; Nishiyama, Y. Macromolecules 1991, 24, 2334. 41. DLZ thanks Dr. Steve A. Cohen at BP Amoco Chemical for his assistance in obtaining molecular weight data. 42. Zambelli, A.; Loca telli, P.; Bajo, G .; Bovey, M .A. Macromolecules 1975, 8, 687. 64 Chapter 2 Group 5 Ansa-Metallocenes as Models for Ziegler-Natta Polymerization Catalysts Abstract To further elucidate the origin of stereocontrol in ansa-metallocene Ziegler-Natta polymerization catalysts, a family of ansa-tantalocene complexes has been prepared. The dipotassio ligand salt, K2[Me2Si(CsH4)2], has been utilized for preparation of the tantalocene trimethyl complex, Me2Si(115_ Cs~)2TaMe3 (SpTaMe3). This complex has been characterized by X-ray crystallography. SpTaMe3 may be used as a synthetic precursor for the corresponding tantalocene ethylene-methyl complex, SpTa(112-CH2=CH2)Me. Excess propylene may be added to this ethylene-methyl complex to induce olefin exchange; a mixture of endo and exo propylene-methyl isomers is observed. Metallation of the doubly-silylene bridged ligand, M2[(1,2-SiMe2)2(CsH3)2] (M2Rp) with TaChMe3 yields a bridged dinuclear complex, Rp(TaMe3Cl)2. In contrast, metallation of M2[(1,2-SiMe2)2(4-CMe3-CsH2)(CsH3)] (M2tBuRp) with TaCl2Me3 allows isolation of an ansa-tantalocene methylidene-methyl complex, tBuRpTa(CH2)CH3, as a minor product. The dipotassio ligand salt, K2[(1,2SiMe2)2(4-CMe3-CsH2)(3,5-(CHMe2h-CsH)] (K2tBuThp) when combined with TaChMe3 yields a mixture of [(1,2-SiMe2h(ll5-4-CMe3-CsH2)(112-3,5-(CHMe2hCsH) ]TaMe3 and [(1,2-SiMe2h(ll5-4-CMe3-CsH2)(115-3 ,S-(CHMe2)2CsH)]Ta(CH2)CH3. Both complexes have been characterized by X-ray crystallography. Thermolysis of this methylidene-methyl complex promotes conversion to the corresponding ethylene-hydride complex, tBuThpTa(ll2CH2=CH2)H. This ethylene-hydride complex undergoes olefin exchange with propylene and styrene to form the olefin-hydride complexes, tBuThpTa(ll2CH2=CHR')H (where R' is methyl or phenyl). Both olefin-hydride complexes have been analyzed by Nuclear Overhauser difference NMR spectroscopy to determine the relative orientation of the bound olefin. These model systems have provided a more thorough understanding of stereocontrol with ansametallocene catalysts. 65 Introduction Understanding mechanisms of stereocontrol in ansa-metallocene ZieglerNatta polymerization catalysts has been an area of intense study since the infancy of these catalysts) Brintzinger's report of isotactic polypropylene formation utilizing the C2-symmetric, rae-ethylene bisindenyl zirconocene dichloride as a precatalyst2 provided important insight into how metallocene symmetry affects polymer microstructure. Later work by Ewen suggested that C 5-symmetry may be necessary for the formation of syndiotactic polypropylene; h e and others have employed C5 -symmetric, singly-linked cyclopentadienylfluorenyl zirconocenes for propylene polymerization.3 Further studies in our group established additional requirements for syndiospecific polymerization catalysts; this work culminated in the introduction of a family of C5 -symmetric, doubly-silylene bridged ansa-zirconocenes (RThpZrCl2) for production of highly syndiotactic polypropylene.4 These zirconocene precatalysts and the polypropylene microstructures they provide are illustrated in Figure 1. m r r Figure 1 : Metallocene symmetry exerts an influence on resulting polypropylene microstructure. Selec t C2-symmetric zirconocen es may be used for the preparation of isotactic polymer (high m diad content). Select C5 -symmetric zirconocenes may be used for the preparation of syndiotactic polymer (high r diad content). While the relationship between metallocene symmetry and polymer microstructure is becoming more well understood, the important stereodirecting interactions during olefin insertion that provide polymers with high stereospecificity and controlled molecular weight remain unclear. Prior studies 66 have established that prevalent 2,1-olefin insertions limit polymer molecular weight. 5 For example, RThp zirconocene catalysts can provide very high molecular weight polymers and exhibit negligible 2,1-olefin insertions (exo olefin coordination). This may be attributed to steric interactions between the incoming a-olefin and the dimethylsilyl methyl groups that orient themselves towards the metallocene wedge, as illustrated in Figure 2. This suggests the importance of ligand array in dictating olefin coordination preferences (endo versus exo). A systematic study of diastereomeric preferences for olefin coordination for a range of arzsa-metallocenes has not been achieved to date. 1,2-insertion favored 2,1-insertion disfavored Figure 2: Doubly-silylene bridged zirconocenes favor 1,2-olefin insertion over 2,1-olefin insertion. Prior studies have probed the important stereodirecting interactions that operate in the formation of isospecific poly(a-olefins). Pino et al. were the first to report the absolute enantioselectivity for a -olefin insertion into metal-hydride and metal-alkyl bonds of ansa-zirconocene polymerization catalysts.6 Optically pure ethylene bis(4,5,6,7-tetrahydroindenyl) zirconocene dichloride was used to prepare low molecular weight hydrooligomers. Polarimetry measurements of select fractions suggest that olefin insertions into metal-hydride and metal-rzpentyl bonds proceed from opposite enantiotopic faces of 1-pentene. More recently, Gilchrist and Bercaw utilized an isotopically chiral olefin as a more sensitive probe for measurement of olefin insertion stereoselectivity? An optically pure yttrocene, (R,S)-BnBpY-R (where R isH or rz-pentyl), was employed to determine the absolute enantioselectivity for 1-pentene insertions into yttrocene-hydride and yttrocene-rz-pentyl bonds. Insertions of 1-pentene into Y-H and Y-rz-pentyl bonds were found to proceed with opposite olefin enantiofaces (as illustrated in Figure 3). In addition, while insertion into Y-H 67 exhibits low enantioselectivity (ee"" 33%), insertion into Y-n-pentyl is highly enantioselective (> 95% ee). Figure 3: Proposed a-olefin insertion into yttrocene-hydride and yttrocene-polymer moieties. These olefin insertion preferences with C2-symmetric, isospecific metallocenes have been extended to predict preferences for C5 -symmetric, syndiospecific metallocenes. For example, the a-olefin insertion transition state for RThp zirconocene polymerization catalysts has been postulated (see Figure 4). It is presumed that the bulky diisopropyl-substituted cyclopentadienyl ring forces the polymer chain towards the R-substituted cyclopentadienyl ring, and the alkyl substituent of the incoming a-olefin is oriented trans with respect to the ~-carbon of the polymer chain. In fact, the open region between the isopropyl substituents was designed to readily accommodate this alkyl substituent. ~ :j: ~ .._________ ./ • Figure 4: A proposed transition state for a-olefin insertion into a growing polymer chain for a C 5 -symmetric, RThp m e tallocene. While previous studies have demonstrated that enantiofacial preferences for olefin insertion into metal-hydride and metal-n-pentyl bonds of C2symmetric metallocenes differ, similar preferences for C5 -symmetric metallocenes (such as RThp metallocenes) have not been examined directly. If olefin insertions into metal-hydride and metal-alkyl bonds of RThp metallocenes proceed with opposite enantiofaces (as observed for C2-symmetric metallocenes), intermediates such as those illustrated in Figure 5 may be operating. An understanding of olefin coordination and insertion for C5- 68 symmetric metallocenes may further our understanding of the mechanism of syndiospecific a-olefin polymerization. More generally, examination of olefin coordination and insertion for a range of ansa-metallocenes may provide valuable insight into the origins of stereocontrol in Ziegler-Natta a-olefin polymerization. R ~R' ""s· favored? ~ ...,. P ~ fa vored ? Figure 5: Potential olefin insertion preferences into metal-hy dride and metal-polym e r bonds for C 5 -symmetric, RThp metallocenes. In order to probe these important stereocontrol issues, a family of ansa- tantalocene complexes has been prepared. Unlike neutral group 3 or cationic group 4 metallocenes, group 5 metallocenes may stabilize olefin adducts through n-backbonding. Isolation and characterization of these olefin adducts may allow an investigation of olefin coordination preferences for both metal-hydride and metal-alkyl complexes. Variation of ligand array (singly versus doubly-silylene bridged metallocenes with different substitution patterns, see Figure 6) may provide insight regarding the importance of ligand sterics and electronics in olefin coordination. This may furnish an understanding of diastereomeric w here R is hydride or alkyl Figure 6: Sing ly- and d oubly-s ilylen e linked tantalocen e o lefin-hydride and olefin-alkyl complexes are d esired as model complexes for Ziegler-Na tta polymerization cata lysts. p references for olefin coordination (endo versus exo, etc.). Also, olefin equilibration reactions may supply information regarding the relative g round 69 state energies of distinct tantalocene olefin adducts. Overall, it is hoped that these ansa-tantalocene olefin-hydride and olefin-alkyl complexes may ser ve as models for the olefin insertion transition state in Ziegler-Natta polymerization. Few ansa-metallocenes incorporating group 5 transition metals have been reported to date. Green and coworkers have prepared a series of isopropylidene-linked niobocene dichloride complexes via reaction of deprotonated ligand salts with NbC4(THF)2.8 Select metallocenes may be converted to the corresponding borohydrides, yet subsequent conversion to niobocene olefin-hydride complexes has been unsuccessful to date. Dimethylsilyl-linked niobocene dichloride have been prepared similarly, and select a lkyne-chloride complexes have also been reported.9 More recently, Parkin has described the synthesis of the ansa-tantalocene, Me2Si(TJ5_ CsMe4)2TaH3.lO This tantalocene is prepared by metallation of the distannylated ligand with TaCls, reduction of the resulting trichloride complex with LiAl~, and subsequent hydrolysis. Addition of ethylene to the tantalocene trihydride complex and thermolysis (80°C, hours) affords the corresponding ethylenehydride complex, Me2Si(TJS-CsMe4)2Ta(T]2-CH2=CH2)H. This is the first reported example of a group 5 ansa-metallocene olefin-hydride complex. The use of TaChMe3 as a metal source for the preparation of ansatantalocenes has not been explored previously. This starting material has been utilized for the preparation of unlinked tantalocene trimethyl complexes; select metallocenes may serve as synthetic precursors to tantalocene olefin adducts. Moreover, the preparation o f ansa-tantalocene complexes from distannylated ligands and TaCls has some synthetic limitations (vide infra). Thus, our initial synthetic efforts directed towards the preparation of ansa-tantalocene olefin adducts have mirrored these prior investigations. Schrock and coworkers have described the utility of TaCbMe3 for the preparation of unlinked tantalocene trimethyl complexes, such as (TJS_ CsHs)2Ta(CH3)3 (Cp2TaMe3).11 These complexes have been used as synthetic precursors to tantalocene e thylene-methyl complexes, as illustrated in Figure 7. Trityl tetrafluoroborate may be used to abstract a methyl group from the tantalocene trimethyl complex. Subsequent reaction of the cationic tantalocene dimethyl complex with base, such as methylidene trimethylphosphorane, affords 70 the corresponding tantalocene methylidene-methyl complex. The methylidenemethyl complex is unstable in solution at 25°C and undergoes facile bimolecular decomposition to afford one equivalent of [Cp2TaMe] (not detected by lH NMR spectroscopy) and one equivalent of Cp2Ta(112-CH2=CH2)Me. This bimolecular decomposition pathway has been supported by trapping experiments with donor ligands, such as ethylene, trimethylphosphine, dimethylphenylphosphine, and carbon monoxide; Cp2Ta(CH3)L complexes are formed. Figure 7: Cp2TaMe3 may be used as a synthe tic precursor to the corresponding tantalocene ethylene-methyl complex. In contrast, reaction of [(115-CsMes)2Ta(CH3)2][BF4] ([Cp*2TaMe2][BF4]) with base, such as potassium hydride, affords the corresponding methylidenemethyl complex which is stable in solution at 25°C. Thermolysis (at 140°C) of this complex induces intramolecular a-migratory insertion to yield the ethylenehydride complex, (115-CsMes )2Ta(112-CH2=CH2)H.l2 This reaction pathway is illustrated in Figure 8. The increased steric bulk of the bispentamethylcyclopentadienylligand framework appears to inhibit the bimolecular decomposition pathway observed for the bis-cyclopentadienyl tantalocene methylidene-methyl complex. 71 Figure 8: [Cp*2TaMe2][BF4] may be used as a synthetic precursor to the corresponding tantalocene ethylene-hydride complex. Results and Discussion Singly-silylene bridged ansa-tantalocenes Preparation of ansa-tantalocene complexes incorporating the singlysilylene linked ligand, Me2Si(CsH4)2, was an attractive initial synthetic target due to the simplicity of the ligand array. The ansa-tantalocene trihydride complex, Me2Si(115-CsH4)2TaH3, has been prepared in our laboratories as a synthetic precursor to the corresponding ethylene-hydride complex.l3 In contrast to Me2Si(11S-CsMe4)2TaH3, thermolysis of Me2Si(11S-CsH4)2TaH3 in the presence of excess ethylene provides a mixture of ethylene-hydride and ethylene-ethyl complexes. This result provided additional motivation for the preparation of ansa-tantalocene trimethyl complexes as synthetic precursors for olefin adducts. Reaction of the dilithio ligand salt, Li2[Me2Si(Cs~h] (Li2Sp ), with TaChMe3 in benzene-d6 provides a mixture of two products: Me2Si(115_ CsH4)2(TaMe3Cl)2 [Sp(TaMe3Cl)2] and Me2Si(11S-CsH4)2TaMe3 (SpTaMe3, 1), as illustrated in eq. 1. These products have been identified by lH NMR spectroscopy; the tantalum-methyl resonances are diagnostic. The bridged 72 dinuclear complex, Sp(TaMe3Cl)2, comprises the majority of the product mixture. Preparative scale metallation of LizSp with TaCizMe3 in diethyl ether affords the bridged dinuclear complex as the sole isolable product.14 benzene-d6 + 1 The desired tantalocene trimethyl complex (1) may be generated as the major product by use of the dipotassio ligand salt, Kz[Me2Si(CsH4)z] (KzSp) for metallation. Dropwise addition of a dilute diethyl ether solution of TaClzMe3 to a slurry of KzSp at 25°C was employed to maximize formation of the desired ansa-metallocene. Complex 1 may be isolated as an off-white powder in 19.8% yield .IS Slow cooling of a diethyl ether solution of 1 provides transparent crystals that are suitable for X-ray diffraction. Figure 9 contains the solid state structure of 1; the space group is P2(1)/n. This structure does not contain any unusual features. The cyclopentadienyl rings display ,s, 115 hapticity with 2.215 A distances from tantalum to each cyclopentadienyl centroid. The tantalum-methyl bonds of 2.300 A (Ta-C13), 2.277 A (Ta-C14), and 2.310 A (Ta-C15) are standard tantalum-alkyl bond lengths. 73 C14 Figure 9: Molecular structure of 1 with selected atoms labeled (50% probability ellipsoids). Hydrogen atoms are omitted for clarity. The lability of the tantalum-methyl ligands of 1 has been examined. Addition of 4 atm of dihydrogen to a benzene-d6 solution of 1 provides no reaction. Since 1 is an 18 electron, coordinatively saturated complex, this lack of reactivity was not surprising. Combination of 1 with one equivalent ZnClz in benzene-d6 solution also provides no reaction, presumably due to the low solubility of ZnClz in this solvent. Reaction of 1 with one equivalent HCl in methylene chloride-d2 affords the tantalocene dimethyl-chloride complex, MezSi(115-CsH4)2TaMe(Cl)Me (SpTaMe(Cl)Me, 2), where the central methyl group has been protonated to form the C2v-symmetric product (eq. 2). Addition of one or two equivalents HCl to 2 does not provide the expected tantalocene methyl-dichloride and trichloride complexes, respectively; a mixture of products and decomposition are observed instead. 1 equiv HCl (2) CD2Cl2 -CH4 2 74 Addition of one equivalent of either trityl tetrafluoroborate or trityl hexafluorophosphate to 1 in methylene chloride liberates Ph3CCH3 and provides the corresponding cationic tantalocene dimethyl complex. Trityl tetrafluoroborate has been used to generate [Me2Si(11S-CsH4)2TaMe2][BF4] ([SpTaMe3][BF4], 3) on a preparative scale (eq. 3); 3 has been isolated as a bright yellow powder in high isolated yield (89.6%). Complex 3 is sparingly soluble in methylene chloride-d2; consequently, only lH and 19F NMR spectroscopy have been used for characterization purposes. Ph3CBF4 CH2 Cl2 - Ph3CCH3 (3) The reactivity of 3 towards various bases such as LiCH(SiMe3)2, LiCH2(SiMe3), and LiN(SiMe3)2, has been examined. Reactions have been carried out in benzene-d6 and monitored by lH NMR spectroscopy. At short reaction times the methylidene-methyl complex, Me2Si(11S-CsH4)2Ta(CH2)CH3 (4), is observed. Over the course of 24 hours the ethylene-methyl complex, Me2Si(115_ CsH4)2Ta(112-CH2=CH2)CH3 (4), becomes the only metallocene product detected in the reaction mixture. Use of a sterically hindered base, such as LiCH(SiMe3)2 or LiN(SiMe3)2, minimizes formation of impurities. The reaction pathway for conversion of 3 to 5 is illustrated in eq. 4. 75 Diagnostic resonances for complexes 4 and 5 have been observed by lH and 13C NMR spectroscopy. The methylidene-methyl complex displays a singlet at 10.30 ppm in the lH NMR spectrum for the methylidene hydrogens. The lH NMR spectrum of the ethylene-methyl complex contains two triplets at 1.23 and 0.96 ppm that correspond to the hydrogens of the bound ethylene. The carbons of the bound ethylene resonate at 26.53 and 18.89 ppm, and the tantalum-methyl carbon is observed at -4.54 ppm. The proposed mechanism for formation of 5 is analogous to the bimolecular decomposition pathway illustrated in Figure 1. Two equivalents of the methylidene-methyl complex, 4, may combine to form a bimolecular intermediate that disproportionates to generate one equivalent of 5 and one equivalent of a tantalum(III) methyl complex, [Me2Si(T]5-CsH4)2TaCH3], that is not observed by lH NMR spectroscopy. This reaction pathway has been probed by addition of donor ligands, such as ethylene and propylene, to trap the putative tantalocene(III) methyl complex. Indeed, combination of 3 with LiCH(SiMe3)2 in the presence of 25 equivalents of ethylene produces greater than 50% conversion to 5; the control experiment without added ethylene provides less than 50% conversion. Also, combination of 3 with LiCH(SiMe3)2 in the presence of 25 equivalents of propylene yields 5 with some evidence for tantalocene propylene-methyl complexes. These results 76 support a bimolecular decomposition mechanism for formation of 5. Slower observed rates for conversion of the more sterically encumbered [Me2Si(115_ CsH4)(115-2,4-(CHMe2)2-CsH2)]Ta(CH2)CH3 to the corresponding ethylenemethyl complex also are in accord with a bimolecular decomposition mechanism.13 Consequently, complex 5 has been prepared on a preparative scale by combination of 3 with LiCH(SiMe3)2 under an atmosphere of ethylene; recrystallization from pentane affords 5 as a pale tan solid. Olefin exchange has been demonstrated with 5; addition of excess propylene to 5 in benzene-d6 solution affords two new olefin adducts (6a, 6b) in a 1.70: 1 ratio, as evidenced by lH NMR spectroscopy. These propylene-methyl complexes exhibit characteristic lH NMR resonances for the propylene-methyl substituents (doublets at 2.04 and 1.92 ppm). NMR analysis is consistent with the formation of endo and exo propylene adducts, as illustrated in eq. 5. + - (5) benzene-d6 0.37 A preference for formation of the endo isomer may be attributed to unfavorable steric interactions in the exo isomer between the propylene-methyl substituent and a silyl-methyl substituent of the ligand. A comparison of the endo : exo ratio for 6 and other linked and unlinked niobocene and tantalocene propylene-hydride complexes is provided in Table 1. 77 molecular formula %endo %exo reference Cp2Nb(CH2=CHCH3)H Cp*2Nb(CH2=CHCH3)H 50% 100% 16 Cp2Ta(CH2=CHCH3)H Cp*2Ta(CH2=CHCH3)H iPrSpTa(CH2=CHCH3)H 50% (100%) 100% 50% 0% 50% (0%) tBuSpTa(CH2=CHCH3)H SpTa(CH2=CHCH3)Me 100% 100% 63% O'Yo 0% 0% 37% 17 18 19 20 20 * Table 1: Comparison of percent endo versus percent exo product for niobocene and tantalocene propylene adducts. * denotes data from this work. Contrasting 6 with its unlinked, niobium counterpart Cp2NbCn2CH2=CHCH3)H suggests that the ansa-bridge enforces a slight preference for the endo isomer. Two different endo to exo ratios have been reported for Cp2Ta(112-CH2=CHCH3)H.l 8 When Cp2Ta(11 2-CH2=CHCH3)H is generated by reaction of Cp2TaCb with two equivalents of i-PrMgCl, a 1 : 1 ratio of endo to exo isomers is observed. In contrast, when two equivalents of n-PrMgCl are employed, the endo isomer is the exclusive product. The sterics towards the sides and back of the metallocene wedge of 6 appear to be less significant than those of Cp*2M(112-CH2=CHCH3)H (where M = Nb, Ta), where exclusive endo olefin coordination is enforced. Similarly, ansatantalocenes of the form [Me2Si(115-CsH4)(11S-3-R-CsH2)]Ta(11 2-CH2=CHCH3)H (RSpTa(CH2=CHCH3)H, where R = CMe3, CHMe2) display exclusive endo coordination of propylene. From this data, it appears that joining cyclopentadienylligands with a dimethylsilyllinker plays a small yet significant role in hindering exo propylene coordination. The equilibrium described in equation 5 has been analyzed to determine the equilibrium constant, free energy change (at 298 K), and relative ground state energies (G.S.E.) for 5 and 6 (Table 2) . When appropriate, the equilibrium constants in Table 2 were each calculated as an average of Keq(endo) and Keq(exo) . Calculation of relative G.S.E. requires consideration of the contributions of free olefin to the equilibrium. Since coordination of an olefin to tantalum or niobium involves partial reduction of the double bond, olefin 78 hydrogenation may be used as a model reaction. Free energies of hydrogenation for ethylene and propylene21 were used to determine the relative G.S.E. of 5 and 6. This type of analysis has been used previously.17,22 Equilibration between ethylene and propylene adducts is illustrated in Figure 10 in a more general fashion. molecular formula Cp2Nb(T12-CH2=CHR')H Cp*2Nb(T12-CH2=CHR')H SpTa(T)2-CH2=CHR')Me Keq298 3.0 (5) X 10-3 6.9 X 10-4 9.2 X 10-4 ~c · reference (kcal/mol) relative G.S.E. 3.4 (4) 2.9 (2) 4.1 3.7 (4) 1.1 2.4 16 17 * Tabl e 2: Equilibrium data for ethylene (R' = H) and propylene (R' = Me) adducts, as described in Figure 10. *denotes signifies the data from this work. .... Figure 10: General equation for equilibration of m e tallocene e thylene and propylene adducts. Development of a Ta(IV) starting material Recently, ansa-tantalocene dichloride complexes of the form [Me2Si(T15_ Cs~)(Tl5-3-R-CsH2) ] TaC12 (RSpTaCl2, where R = CMe3, CHMe2) and [Me2Si(T15_ Cs~)(Tl5-2,4-(CHMe2h-CsH2) ]TaClz (iPr2SpTaClz) have been employed as synthetic precursors for olefin-hydride complexes.20 These dichlorides have been synthesized using a multistep procedure, as illustrated in equation 6. Some notable aspects of this synthesis are the use of tri-n-butyl tin chloride for stannylation of the dilithio ligand salt and the zinc reduction of the tantalocene trichloride complex to generate the desired tantalocene dichlorides. 79 R~u+ ~_,.Me rAS(Me 2 nBu 3SnCI TaCI 5 [nBu3SnhR-Sp • ~Li+ Me,... ~....D Me,.:s~""g R (where R = 3-CHMe2, 3-CMe3, or 2,4-CHMe2 ) \ ~ndust \ME ;::§f Me''····si Cl T/ Me,....- ~~"-..,.Cl (6) R Preparation of the analogous ansa-niobocene dichloride complexes may be achieved by combination of dilithio ligand salts and NbCl4(THF)2 (eq. 7).20 The availability of a niobium (IV) starting material eliminates the need for a metallocene trichloride reduction and does not require use of stannylated ligand. (where R = 3-CHMe2 , 3-CMe3) The synthesis of tantalocene dichloride complexes described in equation 15 has some synthetic limitations. Use of n-Bu3SnCl is generally undesirable due to its toxicity. Also, stannylation of dilithio ligand salts is limited in ligand scope. Bulky ligand arrays such as tBuThp and Bp 14 are not amenable to distannylation. Moreover, the number of required reactions is greater than in preparation of the analogous niobocene complexes (eq. 7). This is due the lack of a suitable Ta(IV) precursor to date. 80 The number of Ta(IV) complexes in the literature are limited.23 Some tantalum tetrachloride adducts have been reported, such as TaCl4(CH3CN)2, TaCl4(pyridine)2,24 TaC4(PMe3)3, and TaCl4(PEt3)2.2s The attempted preparation of TaCl4(THF)2 has also been described. 26 In situ generation of a Ta(IV) species for generation of dicyclopentadienyl tantalocene dichloride is also precedented; i-PrMgBr was used to reduce TaCls to TaCl4 (eq. 8).27 TaCl5 + i-PrMgBr + MgBrCl + [i-Pr•] green suspension - - - - - - 1 - TaCl4 Et20 (8) TaCl4 + 2 CpNa - - - - - - - Cp 2TaCl2 + 2 NaCl Et20 Both TaCl4(CH3CN)2 and TaCl4(THF)228 were tested for metallation of the singly-bridged ligand, Li2iPrSp {Li2[Me2Si(3-CHMe2-CsH3)(CsH4))}. These Ta(IV) sources did not afford the desired ansa-tantalocene dichloride complex. DME (1,2-dimethoxyethane) was examined in attempt to prepare a stabilized tantalum tetrachloride complex. Reduction of TaCls with either Al or Zn in DME provided an olive-green solution over the course of hours. Attempts to concentrate the DME solution or isolate the reduction product as a solid resulted in decomposition or unexplained mixtures of products, as evidenced by EPR spectroscopy. However, in situ reduction of TaCls has been employed for preparation of the known complex, iPrSpTaCh (eq. 9).13 Reduction of TaCls by 0.5 equivalents of zinc dust in DME affords an olive-green solution; dropwise addition of this solution to Li2iPrSp (in DME) affords iPrSpTaCh upon workup. This tantalocene dichloride was identified by ambient temperature EPR spectroscopy. Further reaction of this tantalocene dichloride complex with 2.2 equivalents of phenethylmagnesium chloride afforded the corresponding tantalocene styrenehydride complexes, as reported previously. Similar reactions were attempted with a singly linked cyclopentadienyl-fluorenylligand, Li2[Ph2CCCsH4)(C13Hs)] (Li 2Ep ), but the desired metallocenes were not isolated. 81 TaC15 + 0.5 Zn .- - - i DME -0.5 ZnC12 DME As noted above, tantalocene trichloride or dichloride complexes have not been prepared to date with the tBuThp ligand. Attempts to metallate M2tBuThp (where M = Li, K) with TaCls have been unsuccessful. Also, addition of two equivalents of n-Bu3SnCl to M2tBuThp does not yield the desired distannylated ligand, presumably due to the sterics of the diisopropyl substituted cyclopentadienyl ring. Therefore, NbCl4(THF)2 was examined as a starting material for the preparation of corresponding niobocene dichloride complex. Indeed, combination of Li2tBuThp and NbC4(THF)2 in d iethyl ether affords tBuThpNbCb over the course of days at 25°C (eq. 10) . This niobium(IV) complex h as been analyzed b y ambient temperature EPR spectroscopy; in methylene chloride solution it exhibits a characteristic ten line spectrum (93Nb = 100%, S = 9 /2). Further manipulation of this complex to afford olefin adducts is currently in progress. (10) Doubly-silylene bridged ansa-tantalocenes A variety of doubly-silylene bridged ansa-zirconocenes h as been developed in recent years for u se as a-olefin polymerization catalysts (see Figure 11). These catalysts display a range of polymerization activities and produce polymers with markedly different tacticities. Examination of these trends m ay provide a better understanding of the origin of stereocontrol for Ziegler-Natta 82 polymerization catalysts. In turn, this may facilitate the development of new poly(a-olefins). RpZrC1 2 BsZrC12 BrZrC12 TIPZrC12 RThpZrC12 29 32 30 31 Figure 11: RpZrCl2 ~ , BsZrCl2 , BrZrCl2 , TIPZrCl233, and RThpZrCl24 are examples of previously reported doubly-silylene bridged ansa-zirconocene dichloride complexes. Three types of doubly-silylene bridged ligands have been investigated for preparation of ansa-tantalocene complexes as models for Ziegler-Natta catalysts (see Figure 12). The unsubstituted, doubly-silylene bridged ligand, (1,2SiMe2)2(CsH3)2 (Rp ), was chosen for comparison to the singly-silylene linked Sp ligand discussed above. The C5 -symmetric ligand array, (1,2-SiMe2h(4-RCsH2)(CsH3) (RRp, where R = CMe3, CHMe2), has not been reported previously. This ligand was designed to further explore the importance of sterics in doubly-silylene bridged metallocenes. Also, it may provide some insight regarding the relationship between incoming monomer, polymer chain, and ligand array in a-olefin polymerization. Ansa-tantalocenes employing the RThp lig and, (1,2-SiMe2h(4-R-CsH2)(3,5-(CHMe2h-CsH) (RThp, where R = CMe3), were also targeted. The mechanism for stereocontrol employed by RThp metallocene catalysts has received the most attention, primarily due to the high activity and syndiospecificity they can induce. While the mechanisms for propagation and stereoerror formation have been examined by polymerization studies with group 434 and group 335 RThp catalysts, the preparation of group 5 metallocenes may allow further investigation of olefin coordination preferences and the olefin insertion transition state in Ziegler-Natta polymeriz ation. 83 M~ /Me ME\. /Me MtrS~M+ Mzor:~; "Vl,_Si)V I ' Me Me Rp I~ Me Me RRp Figure 12: Doubly-silylene bridged ligand salts targeted for the synthesis of ansa-tantalocen es. Rp ligand Addition of a dilute solution of TaCbMe3 (in THF) to a slurry of dipotassio ligand salt (K2[(1,2-SiMe2)2(CsH3)2}, K2Rp) affords a bridged-dinuclear complex as the major reaction product (eq. 11) in addition to other decomposition products. Following the course of metallation in THF-ds by lH NMR spectroscopy reveals that the major product decomposes under the reaction conditions over the course of days. Use of the dilithio ligand salt (Li2Rp) also provides this bridged-dinuclear complex as the predominant reaction product.l4 One hypothesis for the formation of this bridged-dinuclear complex is the low concentration of the ligand salt under reaction conditions due to poor solubility as compared to TaCl2Me3. Cl Me Me .... ~ f..,Me Ta THF I~"'M Me''''l \ e (11) C l Me major product To a ddress the low solubility of the ligand salts, crown ethers (12-crown-4 or 18-crown-6) were added to the reaction mixture to complex Li+ or K+, respectively. However, in the presence of these crown ethers decomposition is accelerated and no metallocene products could be isolated. A synthetic methodology analogous to that u sed for the preparation of the ansa-tantalocene, Me2Si(CsMe4)2TaH310, was also attempted with the Rp 84 ligand. Transmetallation of Li2Rp with n-Bu3SnCl in diethyl ether affords (nBu3Sn)2[(1,2-SiMe2)2(CsH3)2] ((n-Bu3Sn)2Rp) as an orange oil. Subsequent reaction of the distannylated ligand with TaCls affords a highly insoluble redpurple solid; lH NMR analysis of this product in THF-ds was inconclusive. Reduction of this red-purple solid with LiAlJ-4, and subsequent hydrolysis (with aqueous ammonium chloride) did not provide the desired ansa-tantalocene trihydride complex. The very low solubility of the red-purple tantalocene product suggests the formation of bridged-dinuclear or higher oligomeric structures. Thus, the Rp ligand's lack of cyclopentadienyl substituents appears to favor spanning two tantalum centers. Since these methodologies have not allowed isolation of the desired T]s,T)s ansa-tantalocenes, more substituted doubly-bridged ligand arrays were examined. RRp ligand The RRp ligand array, [(1,2-SiMe2)2(4-R-CsH2)(CsH3)] (RRp, where R = iPr, tBu), was designed to probe its ability to direct olefin binding preferences. To provide a preliminary understanding of the stereodirecting ability of this ligand array, tBuRp zirconocene dichloride has been prepared and utilized for propylene polymerization. It is expected that bulky R substituent (iPr or tBu) will force the methyl substituent of an incoming propylene molecule towards the unsubstituted cyclopentadienyl ring (as illustrated in Figure 13). However, whether the propylene methyl substituent and ~-carbon of the polymer chain exhibit a trans or cis relationship during olefin coordination and insertion is unclear. A trans relationship has been detected for select singly-bridged R -::Pz215~ l+ r '~)-p R .2 disfavored? Figure 13: Both trans and cis relationships between the propylene methyl subs tituent and the I)carbon of the polymer chain m ay be possible for olefin coordina tion. 85 metallocenes6,7 and postulated for other C5 -symmetric, doubly-silylene bridged metallocenes.4 This relationship cannot be probed in a straightforward manner by employing RRp zirconocene polymerization catalysts. For these reasons, RRp tantalocene complexes were targeted. The synthetic route employed for the preparation of RRp ligands is similar to that of other substituted doubly-silylene bridged ligands.36 Preparation of the protio iPrRp ligand was attempted by the addition of Me2SiCb to a -78oC THF solution of Li2iPrSp (eq. 12). The product of this reaction was isolated as a yellow oil; the lH NMR spectrum of the resulting product exhibited a large number of peaks and was difficult to interpret. Subsequent addition of n-BuLi to a diethyl ether solution of the reaction product affords a white solid. Analysis by lH NMR spectroscopy in THF-ds solvent reveals that the product is a mixture of two isomers, Li2[ (1,2-SiMe2)2( 4-CHMe2-CsH2)(CsH3)] and Li2[ (1,2-SiMe2)2(3-CHMe2CsH2)(CsH3)]. A similar observation was made by Herzog in the preparation of M2[(1,2-SiMe2)2(4-CHMe2-CsH2)(3,5-CHMe2-CsH)] (where M = Li, K); 10% of the undesired isomer, Li2[(1,2-SiMe2h(3-CHMe2-CsH2)(3,5-CHMe2-CsH)], was formed. 36 Metallation of Li2iPrRp with ZrCl4 in toluene provides a mixture of product isomers, as anticipated. Separation of [(1,2-SiMe2h(4-CHMe2CsH2)(CsH3)]ZrCb from [(1,2-SiMe2)2(3-CHMe2-CsH2)(CsH3)]ZrCh was not straightforward and thus not pursued further. Me._ Me _M_~-~:-~--~12- c(b--\ ?' /Mer ash Me Me Me (12) p~ Me Me + isomers The tBuRp ligand was prepared in a similar fashion. Addition of Me2SiCh to a -78°C THF solution of Li2tBuSp {Li2[Me2Si(3-CMe3-CsH3)(CsH4)) affords [(1,2-SiMe2h(4-CMe3-CsH2)(CsH3)] (7) as a yellow-white waxy solid (eq. 13). Subsequent deprotonation of 7 with either n-BuLi or KH provides the corresponding dilithio (Li2tBuRp, 8) or dipotassio (K2tBuRp) ligand salts, respectively. Analysis by lH NMR spectroscopy reveals that only the desired 4tBu substituted isomer is formed. The known propensity for tert-butyl 86 substituents to avoid occupying a position alpha to a dimethylsilyllinking substituent has been described previously.37 Me, /Me s· THF as):>-{." (13) I ' Me Me +isomers 7 The corresponding zirconocene dichloride complex was prepared in a standard fashion by addition of toluene to a mixture of 8 and ZrCl4 at -78°C and slow warming to 25°C (eq. 14). The reaction product was extracted away from lithium chloride using petroleum ether and isolated as a yellow-white solid. Examination of the lH NMR spectrum of the reaction product in benzene-d6 indicates that only the desired 4-tBu substituted isomer, [(1,2-SiMe2h(4-CMe3CsH2)(CsH3)]ZrCl2 (tBuRpZrCb, 9), is formed. Notably, use of refluxing toluene for metallation leads to extensive decomposition and 9 cannot be isolated. Me\ / Me u~Si~­ ~s.,.JV-V, I~ toluene Me Me 8 Complex 9 was targeted as an a -olefin polymerization precatalyst in order to assess the stereodirecting ability of the tBuRp ligand array. Towards this end, 9 was activated with 500 equivalents of MAO for propylene polymerization. The reaction was carried out in neat monomer at 0°C. Examination of the polymer tacticity by 13C NMR spectroscopy indicates that the polymer is primarily atactic, with a slight syndiotactic preference ([r] ""'55.6%). The full pentad distribution for this sample is given in Table 3. Other polymerization conditions, such as dilute monomer concentration or higher polymerization temperature, have not been examined to date. 87 [mmmm] [mmmr] [rmmr] [mmrr] [mrmm] [mrmr] [rrrr] [mrrr] [mrrm] [r] 12.26 13.92 14.78 6.19 55.6 [rmmr] 7.23 8.59 7.96 5.21 23.86 Table 3: Pentad analysis for polypropylene produced using catalyst 9. The low syndiospecificity derived from the C5 -symmetric precatalyst, 9, may be accounted for by a facile site epimerization mechanism. This phenomenon has been observed for other doubly-silylene bridged metallocene catalysts under various polymerization conditions.34,35 Since trans and cis relationships between the propylene methyl substituent and the f)-carbon of the polymer chain may be viable for olefin coordination (Figure 13), this adds another dimension to the operating polymerization mechanism. Assuming that the propylene methyl substituent will orient itself away from the tert-butyl group, the possibilities for olefin coordination are illustrated in Figure 14. The possibilities for olefin coordination with the propylene methyl substituent oriented towards the bulky tert-butyl group are omitted for steric reasons. The predicted preferences for olefin coordination and subsequent insertion in Figure 14 are based on presumed unfavorable steric interactions between certain polymer chain configurations and linking dimethylsilyl substituents. The relative energies of trans and cis conformers cannot be determined with this data. R p-A}.i i R R .. .p~ .~J-p ... ~ ~·~ ll Sl ll re ""' r~')-p favored? disfavored? favo red? disfavored? ~ mdiad ~ r diad ~ r diad m diad ~ i: olefin loss, site epimerization, olefin coordination ii: rotation about a-carbon of polymer chain Figure 14: Invoking both a site epimerization mechanism and facile rotation about the a-carbon of the polymer chain m ay explain the atactic polymer formed using the RRp ligand array. 88 Tantalocenes employing the tBuRp ligand were targeted to ascertain how the sterics of this ligand array influence olefin coordination. Trimethyl complexes were sought as synthetic precursors for olefin adducts. Dropwise addition of a THF solution of TaCbMe3 to a -78°C THF solution of Li2tBuRp and slow warming to 25°C provides an orange solution. Removal of THF in vacuo and extraction with toluene affords a brown oil that is primarily the methylidene-methyl complex, [(1,2-SiMe2)2(4-CMe3-CsH2)(CsH3)]Ta(CH2)CH3 (tBuRpTa(CH2)CH3, 10) (eq. 15). The methylidene protons appear as doublets at 9.43 and 9.74 ppm in the lH NMR spectrum; these resonances are characteristic of a tantalocene-methylidene complex. lH NMR analysis provides no evidence of the expected tantalocene trimethyl complex (see eq. 15). Subsequent dissolution of the brown oil in petroleum ether allows recrystallization of 10 as a tan solid in low yield. Me\ / Me LiN ~Li(, 5 (15) ~Si_)V\~, I ' Me Me not observed This metallation reaction was examined more closely by combination of the dilithio ligand salt, Li2tBuRp, and TaCbMe3 in benzene-d6 in the absence of ambient light (eq. 16). Monitoring the reaction by lH NMR spectroscopy reveals that after 3.5 hours, the bridged dinuclear complex, [(1,2-SiMe2)2(4-CMe3CsH2)(CsH3)](TaMe3Cl)2 [tBuRp(TaMe3Cl)2] was present as the predominant reaction product. Two tantalum-methyl resonances of equal intensity at 1.06 ppm and 1.09 ppm are diagnostic for this type of ligand coordination. Fast rotation about the tantalum cyclopentadienyl bond equivalences the three methyl substituents bound to each tantalum center. The tantalocene methylidene-methyl complex (10) is also present yet it comprises only approximately 1.5% of the product mixture. Over time, the ratio of 10 to 89 tBuRp(TaMe3Cl)2 increases but decomposition also becomes more prevalent. Again, there is no evidence of the expected tantalocene trimethyl complex. Cl Me Me......._ ~..-:,Me Ta TaC12Me3 benzene-d6 \ Ta"'"Me = Mt:t'. . d Cl ma;or pro uct M r----,. I· 51 I ~~Me ~- rJ~:Si (16) . ~ .---CH3 + M;;;-t~CH, minor product 10 The mechanism for formation of 10 and the absence of the tantalocene trimethyl complex under these reaction conditions has not been investigated further. These issues will be addressed with reference to RThp tantalocenes. Thermolysis of the methylidene methyl complex, 10, in benzene-d6 causes starting material resonances to diminish and other peaks to grow in the lH NMR spectrum. After four days at 100°C, a small resonance is present at -2.45 ppm that may be attributed to a tantalocene-hydride resonance but a variety of cyclopentadienyl and alkyl resonances are also present (too many to indicate sole formation of a tantalocene ethylene-hydride complex). Upon continued heating, extensive decomposition occurs providing no identifiable products. Some potential tantalocene products are illustrated in Figure 15. Figure 15: Potential products from thermolysis of 10. 90 RThp ligand Reaction of the dipotassio ligand salt, K2[(1,2-SiMe2)2{4-CMe3-CsH2li3,5(CHMe2)2-CsH}] (K2tBuThp), with TaCl2Me3 in benzene-d6 provides a mixture of two products: [(1,2-SiMe2h{TJ5-CsH2-4-CMe3JITJ2-CsH-3,5(CHMe2)2}]Ta(CH3)3 (tBuThpTaMe3, 11) and [(1,2-SiMe2)2{T]5-CsH2-4-CMe3J!TJSCsH-3,5-(CHMe2)2}]Ta(CH2)CH3 (tBuThpTa(CH2)CH3, 12), as illustrated in eq. 17. The unusual T]2-cyclopentadienyl coordination observed for this tantalocene trimethyl complex (vide infra) and the formation of a tantalocene methylidenemethyl complex under these reaction conditions are notable.38 The doublysilylene bridged ligand array appears to induce this unexpected reactivity. Analogous reactivity is observed with K2TMSThp as a ligand source.13 In order to explore the course of this reaction, a variety of reaction conditions have been examined. Order of addition does not alter the product distribution. Mild heating (60°C) also appears to exert little influence on the course of reaction. Addition of base, such as NEt3, or excess ligand salt, K2tBuThp, are other reactionmodifications that do not affect metallation. The product distribution was found to be highly dependent on the presence or absence of ambient light. If the metallation (eq. 17) is conducted in the presence of ambient light, 11 decomposes over the course of 24 hours. Compound 11 does not decompose to form 12; these tantalocenes are formed at different rates under these reaction conditions. In the absence of ambient light, 12 is stable; compound 11 is also formed and is stable under these conditions. Hence, the tantalocene trimethyl and methylidene-methyl complexes may be isolated independently by selective recrystallization. 91 Following the course of metallation in benzene-d6 by lH NMR spectroscopy (in the absence of ambient light) reveals that both 11 and 12 are formed in low yield (24% and 18%, respectively). This, in part, may be attributed to formation of a bridged dinuclear complex (see Figure 16) as an undesired byproduct. MeC! Jvie "' ..-- M e Ta..- \ Me''··Ja,,,Me Cl Me proposed byproduct d ecomposition no reaction Figure 16: While 11 decomposes in ambient light, 12 is stable. A bridged dinuclear complex is formed as a byproduct under select m etallation conditions. The effect of solvent choice on metallation has been examined by monitoring metallation by lH NMR. Various deuterated solvents have been employed providing a range of product distributions. Generally, when tantalocene products are observed, the formation of the trimethyl complex is favored over the methylidene-methyl complex. The relative amount of the bridged dinuclear species (Figure 16) varies with solvent. The use of polar solvents such as CD3CN or THF-ds is unfavorable for metallation. The former leads to decomposition and the latter yields some of the bridged dinuclear species (as a result, K2tBuThp is not completely consumed). When cyclohexane-d12 is used, the bridged dinuclear species is the major product. While metallation in Et20-d10 generates some of the bridged dinuclear species, formation of the methylidene-methyl complex is minimized {11/ 12 z 3.1). Thus, Et20 is the preferred solvent for isolation of 11. Metallation in benzene-d6 minimizes formation of the bridged dinuclear species with a similar tantalocene product ratio (11/12 z 4). Since separation of 12 from the bridged dinuclear structure is difficult due to similar solubility properties, toluene has 92 been utilized for isolation of 12. Recrystallization is crucial for the independent isolation of 11 and 12. The mechanism for formation of 12 is not well understood. Complex 11 does not appear to be a synthetic precursor to 12; dissolution of isolated 11 in benzene-d6 provides no evidence for production of 12 via methane loss over the course of months at 25°C. Also, thermolysis of isolated 11 in benzene-d6 does not promote conversion to 12; instead, decomposition ensues. Formation of 12 does not appear to be promoted by excess dipotassio ligand salt, K2tBuThp. These results are consistent with two independent pathways for formation of 11 and 12. Complex 11 may be synthesized on a preparative scale by slow warming (from -78°C to 25°C) of a diethyl ether solution of K2tBuThp and TaCi2Me3 in the absence of ambient light. Three hours after solvent addition, extraction of the product with diethyl ether and recrystallization affords 11 as an oran ge-yellow solid in reasonable yield (25.6%) . Complex 12 may be isolated preparatively by slow warming (-78°C to 25°C) of a toluene solution of K2tBuThp and TaCi2Me3 in the p resence of ambient light. After three days of reaction, extraction with diethyl ether and recrystallation from petroleum ether affords 12 as a mustard colored solid in modest isolated yield (20.9%). Complexes 11 and 12 have been characterized by lH and 13C NMR spectroscopy. The NMR spectra of 11 do not possess an y unusual features . In benzene-d6, two diagnostic downfield doublets are observed at 9.30 and 9.58 ppm in the 1H NMR spectrum for the methylidene h ydrogens of 12. The methylidene carbon of 12 resonates at 211.26 ppm in the 13C NMR spectrum. These NMR signals for 12 are consistent with other tantalocene methylidenem ethyl complexes, such as Cp2Ta(CH2)CH312 (lH NMR: 8 = 10.11 (s), Ta=CH2; 13C NMR: 8 = 224, Ta=CH2). Slow cooling of a diethyl ether /petroleum ether solution of 11 affords tangerine colored crystals suitable for X-ray diffraction, as illustrated in Figure 17. Compound 11 crystallized in the space group Pnma. This metallocene sits on 93 a crystallographic mirror plane thus contributing to the disorder of the tert-butyl substituent. The 115,112-cyclopentadienyl coordination of 11 was observed previously for the similar compound, TMSThpTaMe3.13 There are few examples of 112-cyclopentadienyl coordination in the literature. Green and coworkers have characterized (115-CsHs)2Ti(112-CsHs) by X-ray crystallography.39 Shapiro has examined Cp2AlMe by X-ray diffraction and observed 112-cyclopentadienyl coordination.40 Select bond distances and angles are listed in Table 4. Figure 17: Molecular s tructure of 11 with selected atoms labeled (50% probability ellipsoids). Hydrogen a toms are omitted for clarity. Slow cooling of a diethyl ether /pentane solution of 12 affords crystals suitable for X-ray diffraction, as illustrated in Figure 18. Compound 12 crystallized in the space group P2(1) /m . This metallocene sits on a crystallographic mirror plane and as a consequence the methylidene and methyl substituents in the metallocene wedge are indistinguishable. Importantly this structural analysis confirms 115 coordination of both cyclopentadienylligands. Select bond distances and angles are provided in Table 4. 94 Figure 18: Molecular structure of 12 with selected atoms labeled (50% probability ellipsoids). Hydrogen atoms are omitted for clarity. select bond distances (A) tBuThpTaMe3 (11) tBuThpTa(CH2)CH3 (12) 2.150 2.349 2.215 2.223 2.129 2.140 0 and bond an:;;les ( ) Ta-CpA Ta-CpB Ta-C14 Ta-C15 C15-Ta-C15A C14-Ta-C14A CpA-M-CpB PlnA-PlnB 113.4 97.6 112.7(2) 2.154 99.3 125.5 67.0(3) Table 4: Select bond distances and bond angles for 11 and 12. It appears that tantalocenes that employ the RThp ligand may not allow three substituents to occupy the metallocene wedge while maintaining standard 115 coordination of both cyclopentadienylligands (Figure 20). This may be a consequence of the dimethylsilyllinking substituents that orient themselves towards the center of the metallocene wedge. The steric bulk of these methyl groups may hamper coordination of substituents in lateral positions of the metallocene wedge. 95 Figure 19: Comparison of molecular structures of 11 and 12 with selected atoms labeled (50% probability e llipsoids). Hydrogen atoms are omitted for clarity. Conversion to olefin-hydride complexes Thermolysis of 12 (at 100°C) in benzene-d6 affords the ansa-tantalocene ethylene-hydride complex, tBuThpTa(112-CH2CH2)(H) (13), over the course of days; the yield of 13 is quantitative by lH NMR spectroscopy. This reaction may be carried out on a preparative scale; heating a toluene solution of 12 to 110°C for three days provides 13 in slightly diminished yields (eq. 18). toluene, 3 days (18) Complex 13 has been characterized by lH and l3C NMR spectroscop y . The tantalocene hydride resonance at -2.05 ppm in the IH spectrum and the ethylene carbon resonances at 21.75 and 23.08 in the 13C spectrum are diagnostic 96 for tantalocene ethylene-hydride complexes. For example, the tantalocene hydride resonance of Cp*2Ta(112-CH2=CH2)H appears at -2.84 ppm in the lH NMR spectrum and the ethylene carbon resonances appear at 20.57 and 14.86 ppm in the 13C spectrum.19 A more thorough assignment of lH NMR resonances has been obtained by use of NOE difference NMR spectroscopy. Presumably, complex 13 is formed via an a-methyl migration to the methylidene fragment and subsequent ~-H elimination from the incipient tantalocene-ethyl complex (as illustrated in Figure 20). Formation of 13 from 12 is analogous to formation of Cp*2Ta(112-CH2=CH2)H by thermolysis of the methylidene-methyl complex, Cp*2Ta(=CH2)(CH3).l 2 The latter thermal rearrangement requires more forcing conditions (heating to 140°C) than conversion of 12 to 13. This rearrangement contrasts the solution behavior of Cp2Ta(=CH2)(CH3) which upon standing undergoes bimolecular decomposition forming one-half of an equivalent of the tantalocene ethylene-methyl complex, Cp2Ta(112-CH2CH2)(CH3).1 1 Similar to the sterically hindered bis-(CsMes) ligand framework, it appears that cyclopentadienyl substitution serves to protect the metal center of 12 such that bimolecular decomposition is prevented. Instead, intramolecular a-migratory insertion affords 13. i: a-methyl migration ii: ~-H elimination Figure 20: Conversion o f 12 to 13 may involve a tantalocene-e thyl complex as an interm ediate. In attempt to capture the tantalocene-ethyl intermediate as a tantaloceneethyl-(L) complex, trimethylphosphine was added to a benzene-d6 solution of 13. No reaction was observed, even upon h eating to 100°C for days. Generation of alkyl-(L) complexes from olefin-hydrides has been reported when L may serve as a n:-acid. For example, addition of CO or CNMe to Cp*2Nb(112-CH2=CHR')H provides the corresponding alkyl-(L) complexes;17 addition of CO to tBuSpTa(T\2CH2=CHPh)H affords the corresponding alkyl-(CO) compound.1 3 The reactivity 97 of n:-acid ligands such as CO or CNMe towards 13 has not been examined to date. Addition of excess ethylene to 13 was attempted to promote conversion to a tantalocene ethylene-ethyl complex. At 25°C, 13 remains intact; thermolysis of 13 (87°C) in the presence of excess ethylene also does not chemically modify 13. Ethylene is not an effective trap for the proposed tantalocene-ethyl intermediate Complex 13 undergoes olefin exchange with both propylene and styrene to afford the corresponding propylene-hydride and styrene-hydride complexes, respectively (eq. 19). Addition of excess propylene to a benzene-d6 solution of 13 results in olefin equilibration over the course of weeks at 25°C. Notably, only one isomer of a propylene-hydride complex is detected in the equilibrium mixture; there are four possible isomers that may be detected (two endo and two exo).41 Since both sides of the wedge are enantiotopic, two enantiomers of the tantalocene propylene-hydride may form. These enantiomers are indistinguishable by lH NMR analysis. In benzene-d6, the lH NMR spectrum of 14a displays a characteristic upfield resonance at -1.85 ppm for the tantalum hydride resonance as well as a doublet at 2.32 ppm for the methyl group of the coordinated propylene. As with propylene, addition of excess styrene results in slow olefin exchange, forming one diastereomer of the tantalocene styrene-hydride complex (14b) (eq. 19). Two enantiomers of the tantalocene styrene-hydride may form that are indistinguishable by lH NMR analysis. The tantalocene-hydride resonance of 14b appears at -1.10 ppm in the lH NMR spectrum, in benzene-d6 solvent. Olefinic carbon resonances at 21.29 and 22.40 ppm in the 13C NMR spectrum are also consistent with a styrene-hydride complex. The ortho, meta, and para styrene substituents are detected in the lH NMR spectrum at 7.47, 7.23, and 6.82 ppm, respectively. The equivalence of both ortho and meta hydrogens suggests that rotation of the phenyl ring is fast relative to the NMR time scale. 98 (19) Difference NOE experiments were used to establish the relative orientation of the bound propylene in 14a in solution. Irradiation of the tantalocene-hydride, cyclopentadienyl resonances, and the propylene methyl substituent provide spectroscopic information that is consistent with the structures illustrated in Figure 21. These data indicate that the preferred diastereomer has the propylene coordinated in an endo fashion with the propylene methyl group directed away from the bulky tert-butyl substituent, nestled in the open region between the isopropyl groups. Unfavorable steric interactions between the propylene methyl group and the dimethylsilylene linkers appear to force coordination of the olefin in an endo arrangement. Formation of this diastereomer is consistent with the model previously proposed for this ligand array in the syndiospecific polymerization of propylene.4 Identification of the observed styrene-hydride complex, 14b, has been accomplished by NOE difference NMR spectroscopy. Irradiation of the tantalocene-hydride, cyclopentadienyl resonances, and styrene resonances provides spectroscopic information that is consistent with the enantiomers illustrated in Figure 21. Irradiation of other ligand resonances (isopropyl, dimethylsilyl, and tert-butyl substituents) also corroborates this structural assignment. The preferred isomer is analogous to the isomer observed in the propylene-hydride case, namely where the olefin is coordinated in an endo arrangement with the phenyl substituent directed between the two isopropyl groups on the cyclopentadienyl ring. It is notable that complexes 14a and 14b exhibit the same thermodynamic preferences for olefin binding despite the increased sterics of bound styrene. 99 Figure 21: Difference NOE experiments indicate that (CH2=CHR'), where R' is methyl or phenyl, coordinates in an endo fashion with the R' s ubstituent directed between the two isopropyl groups of the cyclopentadienyl ring. Both possible enantiomers are shown; they are indistinguishable by l H NMR spectroscopy. Olefin equilibration with 13 has also been achieved with fluorinated styrenes, such as 2,3,4,5,6-pentafluorostyrene and 4-trifluoromethylstyrene. Tantalocene-hydride resonances at -0.77 and -1.00 ppm in the lH NMR spectrum are typical for tantalocene olefin adducts. Isobutylene does not promote olefin exchange with 13, even under forcing conditions (heating to 140°C). Further investigation of these olefin-hydride complexes is currently in progress. This selectivity for CH2=CHR' coordination in an olefin-hydride complex contrasts what has been observed previously for C2-symmetric yttrocenes (vide supra). The selectivity for olefin coordination exerted by the C5 -symmetric tBuThp ligand and the C2-symmetric Bp ligand is illustrated in cartoon fashion in Figure 22. The C5 -symmetric tBuThp ligand array displays some influence on olefin coordination by favoring two enantiotopic tantalocene olefin-hydride complexes. In contrast, the C2-symmetric Bp yttrocene hydride compound exhibits a slight preference for coordination of one olefin enantioface. Two factors may contribute to these differences in olefin coordination. While isolated tantalocene olefin-hydrides are a measure of thermodynamic coordination preferences (ground states), prior measurements with group 3 and cationic group 4 metallocenes are based on kinetic coordination preferences (transition states). However, if the olefin insertion transition state is "early," it follows from the Hammond postulate that the olefin-hydride ground state may serve as a reasonable model for the olefin insertion transition state.42 Metallocene symmetry is likely a more important factor for dictating stereocontrol; while 14a and 14b utilize the C5-symmetric tBuThp ligand array, prior studies have employed C2-symme tric metallocenes. It appears that metallocene symmetry 100 and disposition of ligand sterics may play a more substantial role in olefin coordination than previously postulated. Figure 22: Selectivity for olefin coordination exerted by the C5 -symmetric tBuThp ligand and the C2-symmetric Bp ligand. Conclusions A family of singly- and doubly-silylene linked tantalocene trimethyl and methylidene-methyl complexes have been synthesized and used as synthetic precursors for olefin adducts. These olefin complexes have been utilized as models for olefin coordination in Ziegler-Natta polymerization catalysts. A tantalocene trimethyl complex has been prepared that incorporates the singlybridged [Me2Si(Csfithl (Sp) ligand. This compound has been characterized by X-ray crystallography and employed in the synthesis of the corresponding ethylene-methyl complex, SpTa(Tl2-CH2=CH2)Me. Olefin exchange with propylene provides a mixture of endo and exo propylene-methyl isomers; the preference for endo isomer formation may be attributed to the ansa-bridge. Doubly-silylene bridged ligands, [(1,2-SiMe2)z(CsH3)2] (Rp ), [(1,2SiMe2)2(4-CMe3-CsH2)(CsH3)] (tBuRp), and [(1,2-SiMe2)2(4-CMe3-CsH2)(3,5(CHMe2h-CsH)] (tBuThp) have been targeted for the preparation of ansatantalocenes. While the Rp ligand affords bridged dinuclear and oligomeric complexes under the reaction conditions examined herein, the tBuRp ligand allows isolation of the methylidene-methyl complex, tBuRpTa(CH2)CH3, as a minor product. Thermolysis of this methylidene-methy l complex provides a m ixture of products and decomposition, presumably due to the limited steric protection of the metal center. Metallation of the tBuThp ligand with TaCl2Me3 yields a mixture of [(1,2-SiMe2h(Tl5-4-CMe3-CsH2)(Tl2-3,5-(CHMe2h-CsH)]TaMe3 and [(1,2-SiMe2h(Tl5-4-CMe3-CsH2) (TlS-3,5-( CHMe2)z-CsH)] Ta( CH2)CH3. Both complexes have been characterized by X-ray crystallography. Upon 101 thermolysis, the methylidene-methyl complex undergoes conversion to the corresponding ethylene-hydride complex, tBuThpTa(112-CH2=CH2)H. The ethylene-hydride complex undergoes olefin exchange with propylene and styrene to form the olefin-hydride complexes, tBuThpTa(112-CH2=CHR')H (where R' is methyl or phenyl). Only one isomer is observed in each case, suggesting the importance of ligand array on olefin coordination. These models have provided an enhanced understanding of stereocontrol for ansa-metallocene catalysts. Experimental General Considerations. All air or moisture sensitive chemistry was performed using standard high vacuum line or Schlenk techniques, or in a dry box under a nitrogen atmosphere as described previously. 43 Dinitrogen, dihydrogen, and argon were purified by passage over MnO on vermiculite and activated molecular sieves. Petroleum ether and toluene were distilled from sodium and stored under vacuum over titanocene.44 Tetrahydrofuran, diethyl ether, and dimethoxyethane were distilled from sodium benzophenone ketyl. Benzene-d6 was distilled from LiAllf4 and then distilled from sodium sand before use. Tetrah ydrofuran-ds was distilled from sodium benzophenone ketyl and stored over 4A molecular sieves. Methylene chloride-d2 was distilled from calcium hydride. Anhydrous hydrochloric acid was purchased from Aldrich and used as received. Ethylene was purchased from Matheson and passed through a dry ice / acetone trap before use. In some cases, propylene was purchased from Aldrich and stored under vacuum over triisobutylaluminum. For polymerizations, propylene (99.5% polymer grade) was dried by passage through a Matheson 6110 drying system equipped with an OXISORBTM column. MAO (methylaluminoxane, Albemarle) was prepared by removing toluene in vacuo; the white MAO solid was dried at 25°C for 48 hours at high vacuum. TaChMe3 was prepared according to literature procedures11 and sublimed under static vacuum at 50°C before use. Alkylchlorosilanes were distilled from CaH2 immediately prior to use. LiCH(TMS)2 was prepared by the method of Cowley.45 Potassium bis(trimethylsilyl)amide (KN(TMS)2) was sublimed before use. All dilithio and dipotassio ligand salts were prepared via standard procedures36 unless otherwise noted. All other reagents were purchased from Aldrich and used as received or purified using standard methods.46 102 Instrumentation. NMR spectra were recorded on a Bruker AM500 (lH, 500.13 MHz; 13C, 125.77 MHz) spectrometer, a Joel GX-400 (lH, 399.78 MHz; 13C 100.53 MHz; 19F, 376.1 MHz) spectrometer, a G.E. QE300 (lH, 300.1 MHz) spectrometer, a Varian INOVA 500 (lH, 500.13 MHz; 13C, 125.77 MHz) spectrometer, or a Varian 300 (lH, 300 MHz) spectrometer. All chemical shifts are relative to TMS for lH (residual) and 13C NMR (solvent used as a secondary standard). Nuclear Overhauser (NOE) difference experiments were conducted using a Varian INOVA 500 MHz spectrometer. Elemental analysis was performed at the California Institute of Technology Elemental Analysis Facility by Fenton I. Harvey or at Midwest Microlab in Indianapolis, Indiana. X-ray crystallography was carried out by Dr. Michael W. Day and Lawrence M. Henling using either an Enraf-Nonius CAD-4 diffractometer or a Bruker Smart 1000 CCD diffractometer. Small crystalline fragments were cut under Paratone-N oil and mounted on the diffractometer under a stream of cold N2 gas. Me2Si(11S-CsH4)zTa(CH3b (1). (SpTaMe3). In the dry box a 100 mL round b ottom flask equipped with stir bar was charged with K2Sp (1.35 g, 5.11 mmol) and Et20 (60 mL) was added to provide an off-white slurry. A 25 mL round bottom flask was charged with TaCl2Me3 (1.52 g, 5.11 mmol) and Et20 (15 mL) was added to provide a bright yellow solution. While rapidly stirring the slurry of K2Sp, the solution of TaChMe3 was slowly added dropwise (over the course of 15 minutes) . When the addition was complete, a fine swivel frit assembly was attached and the apparatus was connected to the vacuum line. An atmosphere of Ar was admitted to the reaction and it was left open to a mercury bubbler. After 11 hr of stirring at 25°C, a pale yellow solution was filtered away from a dark yellow precipitate. The solid was washed with Et20 (6 x 15 mL), and solvent was removed in vacuo providing a pale yellow powder. This powder was transferred to a 50 mL round bottom flask equipped with stir bar and a fine swivel frit assembly w as attached. On the vacuum line, Et20 (25 mL) was added by vacuum transfer and then the frit was backfilled with Ar. The solution was cooled to -78°C to recrystallize the desired product; a yellow supernatent was filtered away from an off-white powder. After removal of solvent in vacuo 1 was isolated as an off-white powder; 417 mg (19.8%). Analysis for C1sH23Ta1SiJ: Calculated (Found) C: 43.69 (44.38); H: 5.62 (5.39). lH NMR (benzene-d6): () = -0.04 (s, 6H, (CH3)2Si), 0.47 (s, 3H, Ta-CH3), 0.51 (s, 6H, Ta-CH3), 4.76 (s, 4H, Cp- 103 H), 5.37 (s, 4H, Cp-H). lH NMR (CD2Ch): 8 = -0.24 (s, 3H, Ta-CH3), 0.18 (s, 6H, (CH3)2Si), 0.53 (s, 6H, Ta-CH3), 5.12 (s, 4H, Cp-H), 5.59 (s, 4H, Cp-H). 13H NMR (benzene-d6): 8 = -5.37 ((CH3)2Si), 22.85, 24.89 (Ta-CH3), 90.24, 105.11, 117.64 (Cp). bridged-dinuclear byproduct Sp(TaMe3Cl)2 lH NMR (benzene-d6): 8 = 0.10 (s, 12H, (CH3)2Si), 0.87 (s, 9H, Ta-CH3), 5.66 (s, 4H, Cp-H), 5.83 (s, 4H, Cp-H). Me2Si(11S-CsH4hTa(CH3)(Cl)(CH3) (2). (SpTa(Me)(Cl)(Me)). A J-Young NMR tube was charged with 1 (10.6 mg, 0.0257 mmol) and on the vacuum line CD2Cl 2 was added by vacuum transfer. The solution was cooled to -196°C and HCl (0.0257 mmol) was condensed into the NMR tube at this temperature, the tube was closed and warmed to 25°C. Immediately the solution turned bright yellow in color and 2 was observed by lH NMR spectroscopy. lH NMR (CD2Ch): 8 = 0.56 (s, 6H, (CH3)2Si), 0.62 (s, 6H, Ta-CH3), 5.55 (s, 4H, Cp-H), 6.16 (s, 4H, Cp-H). [MezSi(ll5-CsH4hTa(CH3h][BF41 (3). ([SpTaMezJ[BF4]). A 50 mL round bottom flask equipped with stir bar was charged with 1 (508 mg, 1.23 mmol) and (C6Hs)3CBF4 (406 mg, 1.23 mmol) and a medium swivel frit assembly was attached. On the vacuum line, 30 mL methylene chloride was added by vacuum transfer at -78°C. The solution immediately turned bright yellow in color and precipitate began to form. The reaction mixture was allowed to warm slowly to 25°C. After 19 hr of stirring, the solvent was removed in vacuo and Et20 (25 mL) was added by vacuum transfer. After 2 hr of stirring, a pale yellow-orange solution was filtered away from a bright yellow precipitate. The solid was washed with Et20 (4 x 10 mL) and then solvent was removed in vacuo to provide 3 as a bright yellow powder; 525 mg (89.6%). lH NMR (CD2Cb): 8 = 0.63 (s, 6H, (CH3)2Si), 0.72 (s, 6H, Ta-CH3), 6.07 (s, 4H, Cp-H), 7.35 (s, 4H, Cp-H). 19F NMR (CD2Ch): 8 = -75.5. MezSi(11S-CsH4)zTa(CH2)CH3 (4). (SpTa(CH2)CH3). (transient). lH NMR (CD 2Cb): 8 = 4.59 (s, 2H, Cp-H), 5.67 (s, 2H, Cp-H), 5.75 (s, 2H, Cp-H), 5.90 (s, 2H, Cp-H), 10.28 (s, 2H, Ta-CH2), Me2Si and Ta-Me resonances not located. Me 2Si(ll5-CsH4)zTa(ll2-CHz=CHz)CH3 (5). (SpTa(112-CHz=CH2)CH3). A 50 mL round bottom flask equipped with stir bar was charged with 3 (206 mg, 424 mmol) and LiCH(SiMe3)2 (70.2 mg, 424 mmol) and a fine swivel frit assembly 104 was attached. On the vacuum line, 25 mL methylene chloride was added by vacuum transfer at -78°C. The reaction solution was frozen to -196°C and 1 atm ethylene was admitted to the reaction apparatus. The -196°C bath was replaced with a -78°C bath and the reaction mixture was allowed to warm slowly to 25°C. After 43 hr stirring, solvent was removed in vacuo and 25 mL pentane was added by vacuum transfer. After 2 hr of vigorous stirring, a yellow solution was filtered away from a tan solid. The solid was washed with pentane (4 x 10 mL) and then the solvent was removed in vacuo. In the dry box, the collection flask was transferred to another fine swivel frit apparatus. On the vacuum line, 25 mL pentane was added by vacuum transfer, the swivel frit apparatus was backfilled with Ar and the solution was cooled to -78°C. A cold filtration was used to separate the yellow supernatent from the pale tan solid. Solvent was removed in vacuo to afford 5 as a pale tan solid; 24 mg (13.5%). lH NMR (benzene-d6): 8 = -0.02 (s, 3H, (CH3)2Si), 0.10 (s, 3H, (CH3)2Si), 0.48 (s, 3H, Ta-CH3), 0.96 (t, 2H, CH2=CH2), 1.23 (t, 2H, CH2=CH2), 3.74 (s, 2H, Cp-H), 4.56 (s, 2H, Cp-H), 5.25 (s, 4H, Cp-H). 13C NMR (benzene-d6): 8 = -8.89, -6.88 ((CH3)2Si), -4.54 (Ta-CH3), 18.89, 26.53 (CH2=CH2), 78.74, 87.83, 94.81, 106.45, 123.37 (Cp). Me2Si(11S-CsH4)zTa(CH2=CHCH3)CH3 (6a (endo), 6b (exo)). (SpTa(CH2=CHMe)Me). Me2Si(llS-CsH4)(1l5-3-CHMe2-CsH3)zTaCl2. (iPrSpTaCl2). In the dry box a 50 mL round bottom flask equipped with stir bar was charged with TaCls (602 mg, 1.68 mmol) and Zn dust (55 mg, 0.84 mmol, 0.5 equiv) and a fine swivel frit assembly was attached. DME (25 mL) was added by vacuum transfer at -78°C, then the cold bath was removed to slowly warm the reaction mixture to 25°C. After 12 hr of stirring, an olive-green solution was filtered away from a gray precipitate and solid was washed with recycled solvent (2 x 15 mL). In the dry box, a 250 mL round bottom flask equipped with stir bar was charged with Li2iPrSp (407 mg, 1.68 mmol) and DME (75 mL) was added to provide a pale yellow solution. While stirring this solution at 25°C, the olive-green solution was slowly added dropwise via a pipette. Upon addition the solution changed to re dbrown in color. A fine swivel frit assembly was attached and the reaction mixture was stirred for 16 hr. DME was removed in vacuo and then diethyl ether (50 mL) was added by vacuum transfer. After stirring for 2 hr, solvent was removed in vacuo and petroleum ether (50 mL) was added b y vacuum transfer. 105 The reaction mixture was stirred for 12 hr, and then solvent was removed in vacuo. Methylene chloride (70 mL) was added by vacuum transfer and then a red-brown solution was filtered from an off-white precipitate. The solid was washed with recycled solvent (3 x 30 mL) and then solvent was removed in vacuo to leave a red-black residue in the collection flask. Drying the product under high vacuum provides a black solid. Yield not determined. EPR spectrum consistent with the previously reported spectrum for this complex.l3 [ (1,2-SiMe2)2(1l5-CsH2-4-CMe3Hll 2-CsH-3,5-(CHMe2h}]NbC12. (tBuThpNbCl2). In the dry box a 100 mL round bottom flask equipped with stir bar was charged with Li2tBuThp (417 mg, 0.86 rnrnol) and NbC4(THF)2 (327 mg, 1 equiv) and a fine swivel frit assembly was attached. Diethyl ether (50 mL) was added by vacuum transfer at -78°C, and with the cold bath intact the reaction mixture was left to slowly warm to 25°C. After 120 hr of stirring, solvent was removed in vacuo and petroleum ether (50 mL) was added by vacuum transfer. After stirring for 2 hr, solvent was removed in vacuo and methylene chloride (50 mL) was added by vacuum transfer. A red-brown solution was filtered away from a brown solid, and then the solid was washed with recycled solvent (4 x 30 mL). Solvent was removed in vacuo to leave a brown-black residue in the collection flask. Drying the product under high vacuum provides a black solid; 300 mg (73.9%). This product was analyzed by ambient temperature EPR spectroscopy in methylene chloride solvent; a characteristic ten line pattern was observed for the Nb(IV) nucleus (93Nb = 100%, S = 9 /2) . [(1,2-SiMe2h(CsH3h](Ta(CH3)3Cl)z (Rp(TaMe3Cl)z). In the dry box a 100 mL round bottom flask equipped with stir bar was charged with K2Rp (289 mg, 0.97 mmol) and tetrahydrofuran (60 mL) was added to provide an off-white slurry. In another flask, TaCbMe3 was dissolved in tetrahydrofuran (10 mL). With rapid stirring in the absence of room light, the TaCbMe3 solution was slowly added via pipette to the ligand slurry. A medium swivel frit assembly was attached to the reaction flask and reaction was continued for 12 hr in the absence of room light. Solvent was removed in vacuo, and petroleum ether (60 mL) was added by vacuum transfer. The petroleum ether slurry was stirred for 12 hr in the absence of room light. A yellow solution was filtered away from a yellow precipitate, and the solid was washed with recycled solvent (2 x 40 mL). Solvent was removed in vacuo to provide a yellow-orange residue in the collection flask and a 106 bright yellow solid above the frit. lH NMR analysis of the bright yellow solid reveals that the bridged-dinuclear complex, Rp(TaMe3Cl)2, is the major product. No yield was determined. lH NMR (benzene-d6): 8 = 0.40 (s, 12H, (CH3)2Si), 1.09 (s, 9H, Ta-CH3), 4.89 (d, 4H, Cp-H, J = 2.8), 6.29 (t, 2H, Cp-H, J = 2.8). (n-Bu3Snh[(1,2-SiMezh(CsH3h1 ((n-Bu3SnhRp). In the dry box a 100 mL round bottom flask equipped with stir bar was charged with Li2Rp (1.82 g, 5.53 mmol) and diethyl ether (50 mL). While stirring rapidly, n-Bu3SnCl (3.0 mL, 11.1 mmol, 2 equiv) was slowly added dropwise via syringe. After the addition was complete, a fine swivel frit assembly was attached. After 96 hr stirring at 25°C, a viscous orange solution was filtered away from a white solid. The solid was washed with recycled solvent (3 x 30 mL) and then solvent was removed in vacuo to provide an orange oil in the collection flask. No yield determined. lH NMR (benzene-d6): 8 = 0.38 (s, 12 H, (CH3)2Si), 0.46-1.71 (n-Bu3Sn, overlapping multiplets), 6.49 (s, 2H, Cp-H), 6.85 (s, 4H, Cp-H). [(1,2-SiMezh(4-CHMez-CsH3)(CsH4)] and [(1,2-SiMezh(3-CHMezCsH3)(CsH4)]. (iPrRpHz). A 500 mL round bottom flask equipped with stir bar was charged with Li2iPrSp (10.37 g, 42.81 mmol) and a fine swivel frit assembly was attached. On the vacuum line, 300 mL THF was added via cannula transfer. At -78°C, Me2SiCh (5.2 mL, 42.8 mmol) was added by vacuum transfer and the pale yellow reaction mixture was allowed to warm slowly to 25°C. The reaction mixture was stirred for 20 hr, and then the THF was removed in vacuo. Petroleum ether (150 mL) was added via cannula transfer, and the resulting yellow solution was filtered away from the white solid. The solid was washed with petroleum ether (3 x 50 mL) and then solvent was removed in vacuo to afford iPrRpH2 as a pale yellow oil; 9.08g (74.0%). Liz[ (1,2-SiMezh(4-CHMez-CsHz)(CsH3)] and Liz[ (1,2-SiMezh(3-CHMezCsHz)(CsH3)]. (LiziPrRp). A 250 mL round-bottom flask equipped with stir bar was charged with iPrRpH2 (3.88 g, 13.54 mmol) and a medium swivel frit assembly was attached. On the vacuum line, 125 mL Et20 was added via cannula transfer. At 0°C, 1.6 M n-BuLi (18.6 mL, 29.8 mmol) solution was added via syringe against an Ar counterflow. The reaction mixture was allowed to warm slowly to 25°C. Upon stirring a white precipitate crashed out of the yellow solution. The reaction mixture was stirred for 40 hr, and then the yellow 107 supernatent was filtered away from the white solid. The white solid was washed with Et20 (2 x 50 mL), and then the Et20 was removed in vacuo. Petroleum ether (150 mL) was added to the apparatus via cannula transfer, and the white solid was washed with petroleum ether (2 x 50 mL). Petroleum ether was removed in vacuo and the white solid was dried under high vacuum for 4 hr affording Li2iPrRp; 4.37g (86.8%). Both isomers are isolated in a 3: 2 ratio. Major isomer lH NMR (THF-ds): 8 = 0.19 (s, 12H, (CH3)2Si), 1.12 (t, 6H, ((CH3CH2)20), 1.20 (d, 6H, (CH3)2CH, 6.4 Hz), 3.13 (s, 1H, (CH3)2CH, 8.3 Hz), 3.39 (q, 4H, ((CH3CH2)20), 5.95- 6.20 (overlapping resonances, Cp-H). Minor isomer lH NMR (THF-ds): 8 = 0.27 (s, 12H, (CH3)2Si), 1.12 (t, 6H, ((CH3CH2)20), 1.20 (d, 6H, (CH3)2CH, 6.4 Hz), 2.89 (s, 1H, (CH3)2CH), 3.39 (q, 4H, ((CH3CH2)20), 5.95- 6.20 (overlapping resonances, Cp-H). [(1,2-SiMez)z(4-CMe3-CsH3HCsH4)] (7). (tBuRpHz). A 500 mL round bottom flask equipped with stir bar was charged with Li2tBuSp (4.55 g, 17.76 mmol) and a fine swivel frit assembly was attached. On the vacuum line, 250 mL THF was added via cannula transfer. At -78°C, Me2SiCb (2.2 mL, 17.76 mmol) was added by vacuum transfer and the yellow reaction mixture was allowed to warm slowly to 25°C. The reaction mixture was stirred for 20 hr, and then the THF was removed in vacuo. Petroleum ether (150 mL) was added via cannula transfer, and the resulting yellow solution was filtered away from the white solid. The solid was washed with petroleum ether (4 x 50 mL) and then solvent was removed in vacuo leaving an orange-yellow oil. Under an Ar counterflow the collection flask was transferred to a Kugelrohr assembly and then the orangeyellow oil was Kugelrohr distilled at l00°C and <1 torr yielding 7 as a pale yellow-white waxy solid; 2.68 g (50.2%). Li 2 [(1,2-SiMez)z(4-CMe3-CsHzHCsH3)] (8). (LiztBuRp). A 250 mL round- bottom flask equipped with stir bar was charged with tBuRpH2 (3.32 g, 11.05 mmol) and a medium swivel frit assembly was attached. On the vacuum line, 100 mL Et20 was added via cannula transfer. At 0°C, 1.6 M n-BuLi (15.2 mL, 24.3 mmol) solution was added via syringe against an Ar counterflow. The reaction mixture was allowed to warm slowly to 25°C. Upon stirring a white precipitate crashed out of the yellow solution. The reaction mixture was stirred for 48 hr, and then the yellow supernatent was filtered away from the white solid. The white solid was washed with Et20 (4 x 50 mL), and then the Et20 was removed 108 in vacuo. Petroleum ether (75 mL) was added to the apparatus via cannula transfer, and the white solid was washed with petroleum ether (2 x 50 mL) . Petroleum ether was removed in vacuo and the white solid was dried under high vacuum for 4 hr affording 8 as a Et20 adduct; 1.63 g (46.9%). IH NMR (THF-ds): 8 = 0.19 (s, 12H, (CH3)2Si), 1.12 (t, 6H, ((CH3CH2)20), 1.26 (s, 9H, (CH3)3C), 3.39 (q, 4H, ((CH3CH2)20), 6.03 (t, 1H, Cp-H), 6.11 (s, 2H, Cp-H), 6.14 (d, 2H, Cp-H). [(1,2-SiMez)2(4-CMe3-CsHz)(CsH3)]ZrClz (9). (tBuRpZrClz). A 25 mL round bottom flask equipped with stir bar was charged with 8 (282 mg, 0.726 mmol) and ZrCl4 (169 mg, 1 equiv) and a fine swivel frit assembly was attached. On the vacuum line, 15 mL toluene was added by vacuum transfer at -78°C. The cold bath was removed to allow the solution to slowly warm to 25°C. After 18.5 hr, a yellow-orange solution was filtered away from a white solid. The solid was washed with toluene (3 x 10 mL) and solvent removed in vacuo. Petroleum ether (15 mL) was added by vacuum transfer, the reaction mixture stirred briefly, and solvent removed in vacuo to provide 9 as a pale yellow solid; 107 mg (32.0%). IH NMR (benzene-d6): 8 = 0.29 (s, 6H, (CH3)2Si), 0.52 (s, 6H, (CH3)2Si), 1.45 (s, 9H, (CH3)3C), 6.24 (t, 1H, Cp-H, 2.8 Hz), 6.82 (d, 2H, Cp-H, 1.4 Hz), 6.83 (d, 2H, Cp-H, 1.4 Hz). 13C NMR (benzene-d6): -4.33, 2.51 ((CH3)2Si), 31.99 ((CH3)3C), 33.27 ((CH3)3C), 114.67, 114.91, 115.60, 136.91, 140.30, 144.16 (Cp). Propylene Polymerization Using 9 as catalyst (neat olefin, 0°C) . A 6 oz. high pressure glass reactor equipped with a septum port, large stir bar, and pressure gauge (0-200 psig) was charged with MAO (500 mg, 8.6 mmol) . The reactor was connected to a propylene line (120 psig), and the vessel purged with propylene for approximately 10 minutes. Next the vessel was placed in a 0°C ice water bath and propylene (-25 mL, -0.6 mol) condensed inside. The propylene inlet valve was then closed, and a solution containing the zirconocene catalyst (2.5 mg, 0.0054 mmol) in toluene (0.25 mL) was added to the vigorously stirred MAO/ propylene suspension via a 1 mL Hamilton gas tight syringe through the septum. (The addition requires significant force since the pressure in the reactor is -95 psig.) The reaction mixture was stirred for 25 minutes at 0°C, and then excess propylene was vented through an oil bubbler via a needle in the septum port. In the fume hood, the top was removed from the glass vessel and the reaction quenched with methanol (6 mL) and dilute methanol-HCl (10 mL. 3 :1, v /v). Addition of methanol (50 mL) and 20 minutes of stirring afforded a white 109 solid that was dried at high vacuum at 60°C for 3 hr. Activity: 769 g polymer1g catalyst/hr. Polymer tacticity was determined by 13C NMR, using pentad level analysis as described by Bovey.4 7 A small amount of the polymer sample was dissolved in a 9 : 7 (v /v) mixture of 1,2-dichlorobenzene and benzene-d6, and 13C NMR data was acquired at 306 K. [(1,2-SiMe2)z(4-CMe3-CsH2HCsH3)]Ta(CH2)CH3 (10). (tBuRpTa(CH 2 )CH 3 ). A 250 mL round bottom flask equipped with stir bar was charged with 8 (626 mg, 1.61 mmol). A 100 mL addition funnel with two Kontes was charged with TaCl2Me3 (478 mg, 1 equiv) and a small stir bar. The addition funnel was attached to the top of the reaction flask and a 180° needle valve was placed on top of the addition funnel. On the vacuum line, 125 mL THF was added to the reaction flask by vacuum transfer at -78°C and 25 mL THF was transferred to the addition funnel. While maintaining the reaction solution at -78°C, the apparatus was backfilled with Ar and left exposed to a mercury bubbler during the slow, dropwise addition of the TaChMe3 solution to the ligand solution. After 30 minutes, addition was complete and the reaction solution was orange in color. The cold bath (in a recrystallizing dish) was left intact to allow the solution to slowly warm to 25°C. After 1 day of stirring, THF was removed in vacuo and petroleum ether (75 mL) was added and the reaction mixture stirred briefly, and solvent then removed in vacuo. Inside the dry box a swivel frit assembly was attached to the reaction flask. On the vacuum line, toluene was added by vacuum transfer to provide a brown solution and off-white precipitate. The supernatent was filtered away from the solid and then the solid was washed with toluene (4 x 50 mL) and solvent removed in vacuo. Petroleum ether (50 mL) was added by vacuum transfer, the reaction mixture stirred briefly, and solvent removed in vacuo to provide a brown thick oil. In the dry box, the reaction product was dissolved in petroleum ether (4 mL) and cooled slowly to provide a tan precipitate. The supernatent was removed, the solid washed with chilled petroleum ether (2 x 1 mL), and then the solid was dried under high vacuum. 10 was isolated as a tan powder; 30 mg (3.7%). lH NMR (benzene-d6): 8 = 0.19 (s, 3H, (CH3)2Si), 0.21 (s, 3H, (CH3)2Si), 0.27 (s, 3H, Ta-CH3), 0.31 (s, 3H, (CH3)2Si), 0.35 (s, 3H, (CH3)2Si), 1.41 (s, 9H, (CH3)3C), 5.50 (t, 1H, Cp-H, 2.4 Hz), 5.85 (s, 1H, Cp-H), 5.90 (d, 1H, Cp-H, 1.5 Hz), 6.46 (d, 1H, Cp-H, 1.8 Hz), 6.53 (s, 1H, Cp-H), 9.43 (d, 1H, Ta=CH2, 9.3 Hz), 9.74 (d, 1H, Ta=CH2, 9.3 Hz). 110 [(1,2-SiMezh(4-CMe3-CsHz)(CsH3)](Ta(CH3hClh. (tBuRp(TaMe3Cl) 2 )]. lH NMR (benzene-d6): o= 0.43 (s, 6H, (CH3)2Si), 0.47 (s, 6H, (CH3)2Si), 1.06 (s, 9H, Ta-CH3), 1.09 (s, 9H, Ta-CH3), 1.28 (s, 9H, (CH3)3C), 5.87 (d, 2H, Cp-H, 3.0 Hz), 6.24 (t, 1H, Cp-H), 6.42 (s, 2H, Cp-H). [(1,2-SiMezh{Tl 5-CsHr4-CMe3HT1 2 -CsH-3,5-(CHMezh}]Ta(CH3)3 (11). (tBuThpTaMe3). All synthetic manipulations were carried out in the absence of ambient light. A 250 mL round bottom flask equipped with stir bar was charged with K2tBuThp (1.05 g, 2.27 mmol) and a medium swivel frit assembly was attached. A 50 mL round bottom flask equipped with stir bar was charged with TaCbMe3 (674 mg, 2.27 mmol) and a 180° needle valve was attached. On the vacuum line, Et20 (250 mL) was added to the swivel frit assembly by vacuum transfer to provide an off-white slurry, and Et20 (25 mL) was added to the latter assembly by vacuum transfer to provide a bright yellow solution. The K2tBuThp slurry was cooled to -78°C and the solution of TaCl2Me3 was slowly added via cannula transfer. After 15 minutes of stirring at -78°C, the dry ice/ acetone bath was replaced with a 0°C ice water bath and the reaction apparatus was covered in foil to exclude light. The reaction mixture was stirred for 3 hr, and then an orange solution was filtered away from an off-white solid. The solid was washed with Et20 (3 x 25 mL), and solvent was removed in vacuo to provide 11 as an orange residue; 354.3 mg (25.6%). lH NMR (benzene-d6): o = 0.38 (s, 6H, (CH3)2Si), 0.48 (s, 6H, (CH3)2Si), 1.12 (s, 9H, (CH3)3C), 1.16 (d, 3H, (CH3)2CH, 6.6 Hz), 1.38 (d, 6H, (CH3)2CH, 6.9 Hz), 1.49 (s, 9H, Ta-CH3), 2.72 (m, 2H, (CH3)2CH), 6.6 Hz), 6.51 (s, 1H, Cp-H), 6.59 (s, 1H, Cp-H). BC NMR (benzened6): o= -28.52 (Ta-CH3), -0.60, 5.24 ((CH3)2Si), 21.61, 25.39, 31.63 ((CH3)2CH), 31.93 ((CH3)3C), 32.67 ((CH3)3C), 73.99, 74.05, 75.83, 75.88 (CsH1), 102.36, 118.32, 123.41, 129.63 (CsH2). [(1,2-SiMezh{Tl5-CsHz-4-CMe3HT1 5-CsH-3,5-(CHMez)z}]Ta(CHz)CH3 (12). (tBuThpTa(CH 2 )CH3). A 250 mL round bottom flask equipped with stir bar was charged with K2tBuThp (2.68 g, 5.82 mmol) and TaCbMe3 (1.73 g, 5.82 mmol) and a 180° needle valve was attached. On the vacuum line, 125 mL toluene was added to the reaction flask by vacuum transfer at -78°C. The dry ice / acetone bath cooling bath was removed and the reaction mixture was allowed to warm slowly to 25°C. The reaction mixture was stirred for 72 hr, and then the solvent was removed in vacuo. In the dry box, Et20 (150 mL) was added to the reaction 111 mixture and then the contents were filtered through a bed o f Celite and washed with Et20 (5 x 25 mL) . A 250 mL round bottom flask equipped with stir bar w as ch arged with the brown mother liquor and a fine swivel frit assembly was attached. On the vacuum line the Et20 was removed in vacuo and then 50 mL pentane was added by vacuum transfer. A brown supernatent was filtered away from a yellow precipitate, and the solid was washed with p entane (2 x 25 mL). Solvent was removed in vacuo to provide 12 as a yellow solid; 723 m g (20.9%). lH NMR (benzene-d6): 8 = 0.24 (s, 3H, (CH3)2Si), 0.36 (s, 3H , (CH3)2Si), 0.44 (s, 3H, (CH3)2Si), 0.45 (s, 3H, Ta-CH3), 0.51 (s, 3H, (CH3)2Si), 1.10 (d, 3H, (CH 3)2CH, 7.0 Hz), 1.12 (d, 3H, (CH3)2CH, 5.9 Hz), 1.16 (d, 3H, (CH 3)2CH, 6.6 H z), 1.39 (d, 3H , (CH3)2CH, 6.6 Hz), 1.49 (s, 9H, (CH3)3C), 2.55 (m, 1H, (CH3)2CH, 5.4 Hz), 3.38 (m, 1H, (CH3)2CH, 5.7 Hz), 5.91 (s, 2H, Cp-H), 6.57 (s, 1H, Cp-H), 9.30 (d, 1H, Ta=CH2, 9.8 Hz), 9.58 (d, 1H, Ta=CH2, 9.8 Hz). l3C NMR (benzene-d6): 8 = -2.01 (Ta-CH3), -1.82, -1.40, 3.78, 4.00 ((CH3)2Si), 21.61, 22.20, 28.04, 28.90, 30.18, 30.64 ((CH 3)2CH), 31.16 ((CH3)3C), 33.05 ((CH3)3C), 102.71, 118.67, 123.74 (C5 H 3), 211.26 (Ta=CH2). [ (1,2-SiMez)z{T]5-CsHz-4-CMe3H11 5-CsH-3,5-(CHMez)z}]Ta(T]2-CHz=CHz)H (13). (tBuThpTa(T]2-CHz=CHz)H). A 25 mL round bottom flask equipped w ith stir bar was charged with 12 (121 m g, 0.203 mmol) and a reflux condensor and 180° needle valve were attached. On the vacuum line, 15 mL to luen e was added to the reaction flask by vacuum transfer providing a yellow-brown solution. The apparatus was backfilled with Ar and then heated to reflux. After 72 hr at reflux, the toluene was removed in vacuo, pentane (10 mL) was added by vacuum transfer and then removed in vacuo to provide a brow n solid in 96SYo yield (116 mg) . l H NMR (benzene-d6): 8 = -2.06 (s, 1 H , Ta-H), 0.43 (s, 3H, (CH3)2Si), 0.55 (s, 3H , (CH3)2Si), 0.63 (s, 3H, (CH3)2Si), 0.68 (s, 3H, (CH3)2Si), 0.78 (d, 3H, (CH3)2CH, 6.6 Hz), 0.97 (s, 9H, (CH3)3C), 1.10 (d, 3H, (CH3)2CH, 7.3 H z), 1.11 (d, 3H, (CH3)2CH , 7.2 Hz), 1.37 (d, 3H , (CH3)2CH, 6.6 Hz), 2.97 (m, 1H, (CH3)2CH, 6.9 Hz), 3.40 (m, 1H, (CH3)2CH, 6.5 Hz), 4.13 (s, 1H, Cp-H), 5.81 (s, 1H, Cp-H), 6.35 (s, 1H, Cp-H). 13C NMR (benzene-d6): 8 = -1.53, -0.78, 5.00, 6.14 ((CH3)2Si), 21.75, 23.08 (CH2=CH2), 28.67, 29.18, 29.63, 30.44, 31.93, 33.04, 30.83 ((CH3)2CH, (CH3)3C), 98.36, 110.66, 111.18, 137.72 (Cp) . [(1,2-SiMez)z{115-CsHz-4-CMe3H115-CsH-3,5-(CHMez)z}]Ta(T]2-CHz=CH(CH3))H (14a). (tBuThpTa(T]2-CHz=CHMe)H). A J-Young NMR tube was charged with 112 13 (10.8 mg, 0.0182 mmol) and dissolved in benzene-d6 to provide a red-brown solution. On the vacuum line, the solution was frozen at -196°C and the NMR tube was degassed. Propylene (0.182 mmol) was condensed into the NMR tube at this temperature, the tube was closed and warmed to 25°C. After 19 days at 25°C, a 10: 1 ratio of 14a: 13 was observed. lH NMR (benzene-d6): 8 = -1.86 (s, 1 H, Ta-H), -0.27 (br s, 1H, CH2=CH(CH3)), -0.19 (m, 2H, CH2=CH(CH3)), 0.42 (s, 3H, (CH3)2Si), 0.54 (s, 3H, (CH3)2Si), 0.61 (s, 3H, (CH3)2Si), 0.66 (s, 3H, (CH3)2Si), 0.97 (d, 3H, (CH3)2CH, 6.8 Hz), 1.01 (s, 9H, (CH3)3C), 1.11 (d, 3H, (CH3)2CH, 6.9 Hz), 1.16 (d, 3H, (CH3)2CH, 7.1 Hz), 1.35 (d, 3H, (CH3)2CH, 6.6 Hz), 2.32 (d, 3H, CH2=CH(CH3), 6.6 Hz), 3 .10 (m, 1H, (CH3)2CH, 6.3 Hz), 3.38 (m, 1H, (CH3)2CH, 7.0 Hz), 4.19 (s, 1H, Cp-H), 5.55 (s, 1H, Cp-H), 6.32 (s, 1H, Cp-H). 13C NMR (benzene-d6): 8 = -1.56, -0.91, 3.94, 4.17 ((CH3)2Si), 13.95, 21.77, 21.91 (CH2=CH(CH3)), 23.10, 28.68, 29.19, 29.40, 29.51, 30.67, 30.83, 32.03 ((CH3)2CH, (CH3)3C), 98.32, 110.14, 112.65, 126.66, 139.34, 147.42 (Cp). [(1,2-SiMe2)2{1l 5-CsH2-4-C(CH3>JH11 5-CsH-3,5-(CHMe2)2}]Ta(ll2CH2=CH(C6Hs))H (14b). (tBuThpTa(ll2-CH2=CHPh)H). A J-Young NMR tube was charged with 13 (20.0 mg, 0.0337 mmol) and dissolved in benzene-d6 to provide a red-brown solution. A small amount of a styrene/benzene-d6 solution was added (0.4044 mmol, 12 equiv) and reaction was monitored at 25°C by lH NMR spectroscopy. After 79 days at 25°C, a 10: 1 ratio of 14b : 13 is observed. lH NMR (benzene-d6): 8 = -1.10 (s, 1 H, Ta-H), 0.35 (s, 3H, (CH3)2Si), 0.48 (s, 3H, (CH3)2Si), 0.56 (s, 3H, (CH3)2Si), 0.58 (s, 3H, (CH3)2Si), 0.60 (d, 3H, (CH3)2CH, 6.7 Hz), 0.95 (d, 3H, (CH3)2CH, 7.0 Hz), 1.08 (s, 9H, (CH3)3C), 1.14 (d, 3H, (CH3)2CH, 7.1 Hz), 1.18 (d, 3H, (CH3)2CH, 6.7 Hz), 1.29 (m, 2H overlapping, CH2=CHPh), 2.80 (t, 1H, CH2=CHPh, 12.5 Hz), 3.19 (m, 2H overlapping, (CH3)2CH, 7.2 Hz), 3.63 (s, 1H, Cp-H), 5.62 (s, 1H, Cp-H), 6.43 (s, 1H, Cp-H), 6.82 (t, 1H, C6Hs, para, 7.1 Hz), 7.23 (t, 2H, C6Hs, meta, 8.0 Hz), 7.47 (d, 2H, C6Hs, ortho, 7.9 Hz). 13C NMR (benzene-d6): 8 = -1.84, -0.71, 3.89, 8.82 ((CH3)2Si), 21.29, 22.40 (CH2=CHPh), 28.91, 29.42, 29.80, 31.26, 32.26, 33.13 ((CH3)2CH), 30.67 ((CH3)3C), 78.67, 81.34, 87.07, 102.93, 110.45, 112.08, 121.52, 126.31, 2 not located (Cp ), not located ((CH3)3C), 142.41, 148.40, 156.48, 1 not located (C6Hs) . References 1. Brintzinger, H.H.; Fischer, D.; Miilhaupt, R.; Rieger, B.; Waymouth, R.M. Angew. Chern. Int. Ed. Engl. 1995, 34, 1143. 113 2. (a) Kaminsky, W.; Kuiper, K.; Brintzinger, H.H.; Wild, F.W.P. Angew. Chem. Int. Ed. Engl. 1985,24,507. (b) Roll, W.; Brintzinger, H.H.; Rieger, B.; Zolk, R. Angew. Chem. Int. Ed. Engl. 1990, 29, 279. (c) Wiesenfeldt, H.; Reinmuth, A.; Barsties, X.X.; Evertz, K.; Brintzinger, H.H. J. Organomet. Chem. 1989, 369, 359. 3. Ewen, J.A.; Jones, R.L.; Razavi, A .; Ferrara, J.D. J. Am. Chem. Soc., 1988, 110, 6255. 4. Herzog, T.A.; Zubris, D.L.; Bercaw, J.E. f. Am. Chem. Soc., 1996, 118, 11988. 5. (a) Ewen, J.A. J. Am. Chem. Soc. 1984, 106, 6355. (b) Grassi, A.; Zambelli, A.; Resconi, L.; Albizzati, E.; Mazzocchi, R. Macromolecules 1988, 21 , 617. 6. Pino, P.; Galimberti, M . f. Organomet. Chem., 1989, 370, 1. 7. Gilchrist, J.H.; Bercaw, J.E. J. Am. Chem. Soc., 1996, 118, 12021. 8. a) Chernega, A .N .; Green, M .L.H.; Suarez, A .G. Can. J. Chem. 1995, 73, 1157. b) Bailey, N.J.; Cooper, J.A .; Gailus, H .; Green, M .L.H.; James, J.T.; Leech, M .A. J. Chem. Soc. Dalton Trans . 1997, 3579. c) Bailey, N.J.; Green, M .L.H.; Leech, M .A .; Saunders, J.F.; Tidswell, H.M. f. Organomet. Chem . 1997,538, 111. d) Conway, S.L; Doerrer, L.H.; Green, M.L.H.; Leech , M.A. Organometallics 2000, 19, 630. 9. Antinolo, A.; Martinez-Ripoll, M.; Mugnier, Y.; Otero, A .; Prashar, S.; Rodriguez, A.M. Organometallics 1996, 15, 3241. 10. Shin, J.H.; Parkin, G . Chem. Comm. 1999, 887. 11. Schrock, R.R.; Sharp, P .R. J. Am. Chem. Soc. 1978, 100, 2389. 12. Parkin, G .; Bunel, E.; Burger, B.J.; Trimmer, M.S.; Asselt, A.V.; Bercaw, J.E. J. Mol. Cat., 1987, 41, 21. 13. Chirik, P .J. Ph.D. Thesis California Institute of Technology, 2000. 14. Chirik, P.J.; Bercaw, J.E., unpublished results. 15. A more efficient synthesis of 1 has been developed elsewhere; addition of a THF solution of Li2Sp to a solution of TaChMe3 at -78°C permits isolation of 1 in 50-60% yield. Piers, W .E.; Cook, K.S.C., personal communication. 16. (a) Klazinga, A .H.; Teuben, J.H. J. Organomet. Chem. 1980, 194,309. (b) Burger, B.J.; Santarsiero, B.D.; Trimmer, M.S.; Bercaw, J.E. J. Am. Chem. Soc. 1988, 110, 3134. 17. Doherty, N.M.; Bercaw, J.E. f. Am. Chem. Soc. 1985, 107, 2670. 114 18. Klazinga, A.H.; Teuben, J.H. J. Organomet. Chern. 1978, 157, 413. 19. Gibson, V.C.; Bercaw, J.E.; Bruton, W.J. Jr.; Sanner, R.D. Organometallics 1986, 5, 976. 20. Chirik, P.J.; Zubris, D .L.; Ackerman, L.J.; Bercaw, J.E. manuscipt in preparation. 21. Benson, S.W. Thermochemical Kinetics 2nd Ed.; Wiley and Sons, New York, 1976. 22. Burger, B.J.; Santarsiero, B.D.; Trimmer, M.S.; Bercaw, J.E. J. Am. Chern. Soc. 1988, 110, 3134. 23. Dictionary of Inorganic Compounds. 24. Fowles, G.W.A.; Tidmarsh, D .J.; Walton, R.A. Inorg. Chern. 1969, 8, 631. 25. Cotton, F.A.; Duraj, S.A.; Roth, R.J. Inorg. Chern. 1984, 23, 4046. 26. Fowles, G.W.A.; Tidmarsh, D.J.; Walton, R.A. Inorg. Chern. 1969, 8, 631. 27. Van Baalen, A.; Groenenboom, C.J.; De Liefde Meiijer, H.J. J. Organomet. Chern . 1974, 74, 245. 28. TaCl4(CH3CN)z was prepared by reduction of TaCls by Al in CH3CN solvent for 96 hours at 25°C. TaC4(THF)z was isolated as a viscous redbrown oil, as described previously. 29. Siemeling, U.; Jutzi, P.; Neumann, B.; Stammler, H.G.; Hursthouse, M.B. Organometallics 1992, 11, 1328. 30. Cano, A.; Cuenca, T.; G6mez-Sal, P.; Royo, B.; Royo, P. Organometallics 1994, 13, 1688. 31. Bulls, A.R. Ph.D. Thesis California Institute of Technology, 1988. 32. Mengele, W.; Diebold, J.; Troll, C.; Roll, W.; Brintzinger, H .-H. Organometallics 1993, 12, 1931. 33. Miyake, S.; Bercaw, J.E. J. Mol. Cat. A Chern. 1998, 128, 29. 34. Veghini, D.; Henling, L.M.; Burkhardt, T.J.; Bercaw, J.E. J. Am. Chern . Soc., 1999, 121, 564. 35. Zubris, D.L., Chapter 1. 36. Herzog, T.A. Ph.D. Thesis California Institute of Technology, 1996. 115 37. Coughlin, E.B. Ph.D . Thesis California Institute of Technology, 1994. 38. Chirik, P.J.; Zubris, D.L.; Henling, L.M.; Bercaw, J.E. manuscript in preparation. 39. Lucas, C.R.; Green, M.L.H.; Forder, R.A.; Prout, K.]. Chem. Soc. Chem. Comm. 1973, 97. 40. Fisher, J.D.; Wei, M .-Y.; Willett, R.; Shapiro, P . J. Organometallics, 1994, 13, 3324. 41. Enantiomeric forms are not considered in the total isomer count. 42. Lowry, T.H.; Richardson, K.S. Mechanism and Theory in Organic Chemistry 3rd Ed.; Harper Collins, New York, 1987. 43. Burger, B. J.; Bercaw, J. E. New Developments in the Synthesis, Manipulation , and Characterization of Organometallic Compounds, 1987; Vol. 357. ACS Symposium Series. 44. Marvich, R. H.; Brintzinger, H. H.]. Am. Chem. Soc. 1971, 93,203. 45. Cowley, A. H .; Kemp, R. A . Synth. React. Inorg. Metal-Org. Chem. 1981, 11, 591. 46. Perrin, D. D.; Armagrego, W. L. F. Purification of Laboratory Chemicals, 3rd ed.; Pergamon Press: New York, NY, 1988. 47. Zambelli, A .; Locatelli, P.; Bajo, G.; Bovey, F. A. Macromolecules 1975, 8, 687. 116 Appendix A: GPC Data GPC data for select polypropylene and polypentene samples that appear in Table 8 of Chapter 1. This data was collected with the assistance of Dr. Steve A . Cohen at BP Amoco Chemical. Two of the samples contain a higher molecular weight component: "Samples 20391-050-4 and 20391-050-8 exhibited a long, low amplitude shoulder on the high mol. wt. side of the peaks. This shoulder was verified by a rerun of 050-8 and all four measurements were averaged for the reported data." 117 TEST: GPC_0630: GPC- POLYPROPYLENE I POLYETHYLENE COMPONENT NAME RESULT VALUE UNITS ============================================================= Entry 9 = 20391-050-1 No. Avg. Mol. Wt. Wt. Avg. Mol. Wt. Z Avg. Mol. Wt. Z+1 Avg. Mol. Wt. Wt. Avg./No. Avg. (PDI) Std. Dev. (No. Avg.) Std. Dev. (Wt. Avg.) Std. Dev. (Z Avg.) Std. Dev. (Z+1 Avg.) Std. Dev. (Wt. / No. Avg) - (PDI) ----1 _, 16.0 32.1 51.9 75.0 2.0 0.1 0.0 0.3 1.0 1000 g/mol 1000 g / mol 1000 g / mol 1000 g/mol 0.0 A~cco Multichron V2.ii Analysis N- : (POSPC) 20 20052799,9,1. 1.- "'·r---------------·------- 1111ght ...~...,. 3. 3.0 !2. i \ ~ 4:t. .;: 1. o.~,.. ~ .. .L .. "'·o,.l ..TI.l ..~ .~~ s.5 "·a 11.0 a.s 6.o a.s o.~2 • 5 Ino-llt 3 •0 IIDlaculr lle1D~ llagtOI : a.rau Title : PDO.• L - Ill : 1ININI M:llfUlred 011 21H1o\Y-t- at 01.: l7 - - ... ~1- et • • ---·=~ =~ Clllitl'eUotl : - 118 TEST: GPC_0630: GPC- POLYPROPYLENE I POLYETHYLENE RESULT VALUE COMPONENT NAME UNITS ============================================================= Entry 1 = 20391-050-2 No. Avg. Mol. Wt. Wt. A vg. Mol. Wt. Z A vg. Mol. Wt. Z+1 Avg. Mol. Wt. Wt. Avg./No. Avg. (PDI) Std. Dev. (No. Avg.) Std. Dev. (Wt. Avg.) Std. Dev. (Z Avg.) Std. Dev. (Z+1 Avg.) Std. Dev. (Wt./No. Avg) - (PDI) 86.0 195 356 562 2.3 1000 g/mol 1000 g / mol 1000 g/mol 1000 g/mol 1.6 0.4 2.5 6.7 0.1 AIDco Multlchron V2.11 Analya1s Nlln : (?OGPCJ 20 20052799. iO, i. -~--~ -.nt : S.OIO llel!!l!t f"rKtlon 4.~--------------------------------------~~~~1 I ll. \ !z. ~ s. ... ' •• rF-J&-~~2.--;'6._._.........,.3!-::.o'-'-~3~.5~:ooc::x:'=J-4.~a_._.-L..};t-''--'--'U;h.~..........Hf--'-'--'-i-'P'-'-'-.tll.6 IID~cul.. lle~t tnet......t -Y-- : ~. .1 ntla : """"' U..JO :-.. AIICI'Ilrelll an at oa: •s ....,.rteol an ihllll-11118 at oe 113 Uaaiol ...: PPII!1IIIO caltlll'eU. : - -~:- 119 TEST: GPC_0630: GPC- POLYPROPYLENE I POLYETHYLENE RESULT VALUE COMPONENT NAME UNITS ============================================================= Entry 11 = 20391-050-3 No. A vg. Mol. Wt. Wt. Avg. Mol. Wt. Z A vg. Mol. Wt. Z+1 Avg. Mol. Wt. Wt. Avg./No. Avg. (PDI) Std. Dev. (No. Avg.) Std. Dev. (Wt. Avg.) Std. Dev. (Z Avg.) Std. Dev. (Z+1 Avg.) Std. Dev. (Wt./No. Avg) - (PDI) 3.9 7.5 12.0 16.9 1.9 0.1 0.0 0.0 0.2 1000 g/mol 1000 g/mol 1000 g / mol 1000 g / mol 0.0 Amoco MUltichroa V2 . i1 Anal~BiB Nlllllil : [POSPC] 20 20052699, 4, 1. -Urlt : 1. CJOe l!VII!Ii-«!o-5 ~.~ ------------------ -------------*=1pt~IC~~~ sJ (\ 3 . 0~ §2. ~ .!! a. 1i ,t s. :1: 1. o. ~·~~~~-~. .l~.n~·~l.~·~~~~~.J ~ r..tr-t 3.11 lllttold : c:aJ~tU.. ~1Tltla: u.m -o : t0M211 ~11'111 M -Y..I.S& • "-Pai'Ud . . ~~- - ...,_,_ 4.0 4.6 6.0 IIDlonl.,. WeSJiht 11011101 tRill Qll: 114 : PI'IEIKD : :1!11115 !1.11 11.0 8.6 120 TEST: GPC_0630: GPC - POLYPROPYLENE I POLYETHYLENE RESULT VALUE COMPONENT NAME UNITS ============================================================= Entry 6 = 20391-050-4 No. Avg. Mol. Wt. Wt. Avg. Mol. Wt. Z Avg. Mol. Wt. Z+1 Avg. Mol. Wt. Wt. Avg./No. Avg. (PDI) Std. Dev. (No. Avg.) Std. Dev. (Wt. Avg.) Std. Dev. (Z Avg.) Std. Dev. (Z+1 Avg.) Std. Dev. (Wt./No. Avg) - (PDI) Analysis Naate : !0311l~... l.- 9.3 26.7 133 501 2.9 0.0 0.1 2.6 6.1 1000 g / rnol 1000 g / rnol 1000 g / rnol 1000 g / rnol 0.0 Aaoco Multlchroa V2.11 [PDGPC] 20 20052699,5, i . -- : IIIII t Frt1ct101'1 .&.o....----------------------==:oc:..:'-'-'-"=""1 3.t 3.1 . !a. - ,. ...~ z.oE~ u • .... ~ l.ll l. o. ~= a - 1 111:18 : , _ . swo• L-ID : fllpartlllll aa ~~ at 01: 54 ~ aa ae-tiAT-~ at 21: l8 ---:- C·ll - l a : 1101111 I'PIE11III 121 TEST: GPC_0630: GPC - POLYPROPYLENE I POLYETHYLENE COMPONENT NAME RESULT VALUE UNITS ============================================================= Entry 4 = 20391-050-5 No. Avg. Mol. Wt. Wt. Avg. Mol. Wt. Z A vg. Mol. Wt. Z+1 Avg. Mol. Wt. Wt. Avg./No. Avg. (PDI) Std. Dev. (No. Avg.) Std. Dev. (Wt. Avg.) Std. Dev. (Z Avg.) Std. Dev. (Z+1 Avg.) Std. Dev. (Wt./No. Avg) - (PDI) 13.4 34.0 57.0 1000 g / rnol 1000 g / rnol 1000 g/rnol 1000 g / rnol 81.1 2.5 0.6 0.0 0.4 1.0 0.1 Amoco NUltichro• V2.11 Analya1a Ha•e : [POGPC) 20 20052799, H, 1. ·~ ....nt: 1.1100 4 . - - - - - - - - - - - - - - - - - - - - - - - - = * : 9 1:.:.=..:.fNctton==, -t: -•llltle:- t.w m : -27 ..,.,1rea on - Y - 1 - et 04: 011 Aepa~ an lhU+--1- It I * ID ......... :: l'fiE1tiiD celiiiNtlOII 1!018 ,~ 122 TEST: GPC_0630: GPC- POLYPROPYLENE I POLYETHYLENE RESULT VALUE COMPONENT NAME UNITS ============================================================= Entry 13 = 20391-050-6 No. Avg. Mol. Wt. Wt. A vg. Mol. Wt. Z A vg. Mol. Wt. Z+1 Avg. Mol. Wt. Wt. Avg./No. Avg. (PDI) Std. Dev. (No. Avg.) Std. Dev. (Wt. Avg.) Std. Dev. (Z Avg.) Std. Dev. (Z+1 Avg.) Std. Dev. (Wt./No. Avg) - (PDI) 2.9 8.8 12.4 1.9 0.1 0.0 0.2 0.5 0.1 ~ca Analysis 20311!---tl 1000 g/mol 1000 g/mol 1000 g/mol 1000 g/mol 5.5 Nultlchrom Y2.11 Na•• : [pOGPC] 20 20052699. 6, 1. -unt : 1.«*1 ::Dr---------------------='lfll~tpll~tc.:.Fr.c=t,.,ton~~ !1. --t: Aclllllre• an ~T-M& u -·-=-- :I'PIElMOD 0111~-:- OWIMl TltlAI : u..m ,_. 1!1!: 4D AII>Orb. QCI lhUI-- •t 011: lloC 123 0630: GPC -POLYPROPYLENE I POLYETHYLENE TEST: GPC COMPONENT NAME RESULT VALUE UNITS ============================================================= Entry 14 = 20391-050-7 No. A vg. Mol. Wt. Wt. Avg. Mol. Wt. Z A vg. Mol. Wt. Z+1 Avg. Mol. Wt. Wt. Avg./No. Avg. (PDI) Std. Dev. (No. Avg.) Std. Dev. (Wt. Avg.) Std. Dev. (Z Avg.) Std. Dev. (Z+1 Avg.) Std. Dev. (Wt./No. Avg) - (PDI) 5.3 1000 g/rnol 1000 g / rnol 1000 g/rnol 1000 g/rnol 10.5 16.7 23.3 2.0 0.2 0.0 0.2 0.5 0.1 AIOCO MUlt1chrom V2. 11 Analysis Nau : [POGPC] 20 20052699. 7, 1. 20·1---7 - : 1.000 Wei F~IICtlon 4 ..~------------------~~-----------------=-=~==~ 3. IMtrll_,t : -pc a.....l Title : u.. JD ! 1- Acqut.r811 ae 1!7-IMY-18111 et 00:113 ~- ~•tDII:IU IMthod : PPIE1llll Callllrett.an : 1!0111! -~ = - 124 TEST: GPC_0630: GPC- POLYPROPYLENE I POLYETHYLENE COMPONENT NAME RESULT VALUE UNITS ============================================================= Entry 5 = 20391--050-8 No. Avg. Mol. Wt. Wt. Avg. Mol. Wt. Z A vg. Mol. Wt. Z+ 1 A vg. Mol. Wt. Wt. Avg./No. Avg. (PDI) Std. Dev. (No. Avg.) Std. Dev. (Wt. Avg.) Std. Dev. (Z Avg.) Std. Dev. (Z+1 Avg.) Std. Dev. (Wt./No. Avg) - (PDI) 1000 g/mol 1000 g / mol 1000 g / mol 1000 g / mol 4.5 11.6 69.0 285 2.6 0.1 0.3 5.0 23.2 0.0 AIOCO MUlt1chrom V2.11 Analysis Halle : [POGPC) 20 20052799, 13, 1. 2111311--- Almlmt: s.ooo .c.Gr----------------------'*~l~~Frw:~l:i~on~ ~t:: a - 1 Tttl8 : , _ u.o m : s- M41Srell ., 28-tiAY-~ -" oa a ....,_.. . . ..........- -" 011: ... ...tiiDd : PPIIE1liiiD c.lSIII'ftiMI : 2018 _.._...,_,.. 125 Appendix B: X-ray Crystallographic Data 126 Table 1. Crystal Data and Structure Analysis Details for dlzl[(Me2Si)2(4-CMe3-C5H2)(3,5-CMe2H-C5H1)]Y(J..L-Cl)2K(THF)r Empirical formula C32H54Cl2K1 0 2Si2Y1 725.86 Formula weight Crystallization solvent diethyl ether I tetrahydrofuran/ pentane irregular Crystal shape Crystal color Crystal size colorless 0.190 x 0.200 x 0.330 mm Data Collection Preliminary photograph(s) Type of diffractometer Wavelength Data collection temperature Theta range for 25 reflections used in lattice determination Unit cell dimensions rotation CAD-4 0.7107 A MoKa 160K 11 to 13° a = 10.204(2) A b = 16.220(6) A c = 23.074(7) A a= 90° 13= 91.02(2) 0 y= 90° Volume 3818.3(20) A3 z 4 monoclinic P 21 /n (# 14) 1.263 g / cm3 1528 1.0 to 25.0° 0 :s; h :s; 12,-19 :s; k :s; 15,-27 :s; 1 :s; 27 Crystal system Space group Density (calculated) F(OOO) Theta range for data collection Index ranges Data collection scan type Reflections collected Independent reflections ro scans 12148 6700 [Rint= 0.046; GOFmerge= 1.14] Reflections > 2cr(I) Absorption coefficient 6700 1.866 mm-1 Absorption correction Number of standards Decay of standards not applied 3 reflections measured every 60 min within counting statistics 127 Structure Solution and Refinement Primary solution method direct methods difference map calculated Secondary solution method Hydrogen placement Refinement method Data I restraints I parameters Treatment of hydrogen atoms full-matrix least-squares on p2 6700 I o I 330 R indices (all data) Type of weighting scheme used Weighting scheme used R1 = 0.1099, wR2 = 0.1191 sigma 2 2 w= 1 I cr (Fo ) 0.02 1.50 and -1.43 e·A-3 not refined, uiso fixed at 120% u eq of attached atom Goodness-of-fit on p2 1.65 Final R indices [1>2cr(l), 6700 reflections] R1 = 0.1099, wR2 = 0.1191 Max shift/ error Largest diff. peak and hole Programs Used Cell refinement Data collection Data reduction Structure solution Structure refinement CAD-4 Software (Enraf-Nonius, 1989) CAD-4 Software (Enraf-Nonius, 1989) CRYM (Duchamp, 1964) SHELXS-86 (Sheldrick, 1990) CRYM (Duchamp, 1964) Special Refinement Details A small, irregular, colorless crystal was mounted on a glass fiber with ParatoneN oil. Data were collected with 1.0° ro-scans. The GOFmerge was 1.14 (4027 multiples) in point group 2/m; Rmerge was 0.046 for 2989 duplicates with F 0 > 0. The individual backgrounds were replaced by a background function of 28 derived from the backgrounds of weak reflections. Weights ware calculated as 1/ <f(F0 2 ); variances (<i(F/ )) were derived from counting statistics plus an additional term, (0.0141?; variances of the merged data were obtained by propagation of error plus another additional term, (0.014<1> /. The refinement of F2 is as always against all reflections. The weighted R-factor wR and goodness of fitS are based on F2 , conventional R-factors Rare based on F, with F set to zero for negative F2 . The threshold expression of F2 > 2cr(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. The two tetrahydrofuran molecules are disordered and were not modeled 128 satisfactorily. One, modeled with only on position, has very large displacement parameters for two of the atoms. The other, modeled with two arrangements for the two outside carbon atoms, has a very unrealistic geometry for the minor site (C30B and C31B are 2.09(5)A apart). In fact, it is not possible to rule out the presence of a small fraction of diethyl ether at this location. There is also a much lesser disorder in one of the isopropyl groups. The disorder of these groups should have little effect on the rest of the structure. The K atom is coordinated to the two THF ligands, two chlorides (bridging to Y), and is also TJ 3 coordinated to the t-butyl cyclopentadienyl. This produces helical chains along the b-axis. Table 2. Bond lengths [A] and angles [0 ] for dlzl- [(Me2 Si) 2 (4CMe3-C5H2) (3,5-CMe 2H-C 5 H 1 ) ]Y (J..L-Cl) 2 K(THF) 2 • Y-Cll Y-Cl2 Y-K Y-Si1 Y-Si2 Y-C1 Y-C2 Y-C3 Y-C4 Y-C5 Y-C6 Y-C7 Y-C8 Y-C9 Y-ClO Y-CpA a Y-CpB b Si1-C1 Sil-C6 Si1-Cll Sil-C12 Si2-C2 Si2-C7 Si2-Cl3 Si2-C14 C1-C2 Cl-C5 C2-C3 C3-C4 C3-H3 C4-C5 2.587(2) 2.579(2) 4.266(2) 3.281(2) 3.268(2) 2.590(6) 2.586(6) 2.704(6) 2.828(6) 2.735(6) 2.545(6) 2.548(6) 2.750(6) 2.815(7) 2.737(7) 2.403 2.391 1.847(6) 1.856(7) 1.880(8) 1.856(9) 1.870(6) 1.873(6) 1.877(7) 1.865(7) 1.438(8) 1.428(9) 1.426(9) 1.423(9) 0.95 1.393(9) C4-C15 C5-H5 C6-C7 C6-C10 C7-C8 C8-C9 C8-C19 C9-C10 C9-H9 C10-C22 Cll-Hlla Cll-Hllb Cll-Hllc C12-H12a C12-H12b C12-H12c C13-H13a C13-H13b C13-H13c C14-H14a C14-H14b C14-H14c C15-C16 C15-C17 C15-C18 C16-H16a C16-H16b C16-H16c C17-H17a C1 7-H17b C17-H17c 1.504(9) 0.95 1.480(9) 1.420(9) 1.422(9) 1.397(9) 1.518(9) 1.402(9) 0.95 1.52(1) 0.95 0.95 0.95 0.95 0.95 0.95 0.95 0.95 0.95 0.95 0.95 0.95 1.52(1) 1.53(1) 1.52(1) 0.95 0.95 0.95 0.95 0.95 0.95 129 C18-H 18a C 18-H 18b C18-H 18c C 19-C20 C19-C21 C19-H 19 C20-H20a C20-H20b C20-H20c C21-H21a C21-H21b C21-H21c C22-C23 C22-C24 C22-H22 C23-H23a C23-H23b C23-H23c C24-H24a C24-H24b C24-H 24c K-Cll K-C12 K-01 K-02 K-C1 K-C2 K-C5 01-C25 01-C28 C25-C26 C25-H25a C25-H25b C26-C27 C26-H26a C26-H26b C27-C28 C27-H27a C27-H27b C28-H28a C28-H28b 02-C29 02-C32 C29-C30A C29-C30B C29-H29a C29-H29b C29-H29c C29-H29d 0.95 0.95 0.95 1.525(9) 1.54(1) 0.95 0.95 0.95 0.95 0.95 0.95 0.95 1.51(1) 1.53(1) 0.95 0.95 0.95 0.95 0.95 0.95 0.95 3.163(2) 3.189(2) 2.622(6) 2.751(6) 3.021(6) 3.224(6) 3.285(7) 1.52(2) 1.42(1) 1.33(2) 0.95 0.95 1.50(3) 0.95 0.95 1.45(2) 0.95 0.95 0.95 0.95 1.42(1) 1.43(1) 1.47(2) 1.48(3) 0.95 0.95 0.95 0.95 C30A-C31A C30A-C30B C30A-H30a C30A-H30b C31A-C31B C31A-C32 C31A-H 31a C31A-H 31b C30B-H30c C30B-H30d C30B-C31B C31B-C32 C31B-H31c C31B-H31d C32-H32a C32-H32b C32-H32c C32-H32d 1.50(2) 0.97(4) 0.95 0.95 1.06(4) 1.58(2) 0.95 0.95 0.95 0.95 2.09(5) 1.26(4) 0.95 0.95 0.95 0.95 0.95 0.95 CpA-Y-CpB CpA-Y-Cll CpA-Y-Cl2 CpB-Y-Cll CpB-Y-C12 Cll-Y-Cl2 C6-Si1-C1 C11-Sil-C1 C12-Si1-C1 C11-Si1-C6 C12-Si1-C6 C12-Si1-C11 C7-Si2-C2 C13-Si2-C2 C14-Si2-C2 C13-Si2-C7 C14-Si2-C7 C14-Si2-C13 C2-C1-Si1 C5-C1-Si1 C5-C1-C2 C1-C2-Si2 C3-C2-Si2 C3-C2-C1 C4-C3-C2 H3-C3-C2 H3-C3-C4 C5-C4-C3 C15-C4-C3 C15-C4-C5 115.0 113.1 111.0 109.3 111.1 95.74(6) 96.1(3) 107.4(3) 116.3(3) 116.3(3) 113.5(3) 107.1(4) 95.7(3) 116.8(3) 107.3(3) 115.5(3) 115.3(3) 106.1(3) 122.2(4) 127.2(5) 106.4(5) 123.8(4) 124.9(4) 106.3(5) 110.6(5) 124.7 124.7 105.3(5) 126.9(6) 127.4(6) 130 C4-C5-C1 H 5-C5-C1 H5-C5-C4 C7-C6-Si1 C10-C6-Si1 C10-C6-C7 C6-C7-Si2 C8-C7-Si2 C8-C7-C6 C9-C8-C7 C19-C8-C7 C 19-C8-C9 C10-C9-C8 H9-C9-C8 H9-C9-C10 C9-C10-C6 C22-C10-C6 C22-C10-C9 H11a-C11-Si1 H11b-C11-Si1 H11c-C11-Sil H11b-C11-H11a H11c-C11-H11a H11c-C11-H11b H12a-C12-Sil H12b-C12-Sil H12c-C12-Si1 H12b-C12-H12a H12c-C12-H12a H12c-C12-H12b H13a-C13-Si2 H13b-C13-Si2 H13c-C13-Si2 H 13b-C13-H13a H13c-C13-H13a H13c-C13-H13b H14a-C14-Si2 H14b-C14-Si2 H14c-C14-Si2 H14b-C14-H14a H14c-C14-H14a H14c-C14-H14b C16-C15-C4 C17-C15-C4 C18-C15-C4 C17-C15-C16 C18-C15-C16 C18-C15-C17 H16a-C16-C15 111.4(6) 124.3 124.3 122.3(5) 128.6(5) 106.1(5) 121.9(4) 127.8(5) 106.8(5) 108.5(6) 125.5(6) 125.8(6) 109.5(6) 125.3 125.3 108.9(6) 127.3(6) 123.6(6) 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 110.9(5) 109.0(5) 111.0(6) 108.7(6) 107.5(6) 109.8(6) 109.5 H16b-C16-C15 H16c-C16-C15 H16b-C16-H16a H16c-C16-H16a H16c-C16-H16b H17a-C17-C15 H17b-C17-C15 H17c-C17-C15 H17b-C17-H17a H17c-C17-H17a H17c-C17-H17b H18a-C18-C15 H18b-C18-C15 H18c-C18-C15 H18b-C18-H18a H18c-C18-H18a H18c-C18-H18b C20-C19-C8 C21-C19-C8 H19-C19-C8 C21-C19-C20 H19-C19-C20 H19-C19-C21 H20a-C20-C19 H20b-C20-C19 H20c-C20-C 19 H20b-C20-H20 a H20c-C20-H20 a H20c-C20-H20b H21a-C21-C19 H21b-C21-C19 H21c-C21-C19 H21b-C21-H21a H21c-C21-H21a H21c-C21-H21b C23-C22-C10 C24-C22-C10 H22-C22-C10 C24-C22-C23 H22-C22-C23 H22-C22-C24 H23a-C23-C22 H23b-C23-C22 H23c-C23-C22 H23b-C23-H23a H23c-C23-H 23a H23c-C23-H23b H24a-C24-C22 H24b-C24-C22 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 110.4(5) 113.2(5) 106.5 110.2(5) 109.7 106.7 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 113.5(7) 108.8(7) 107.6 110.7(7) 105.6 110.6 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 131 H24c-C24-C22 H24b-C24-H24a H24c-C24-H24a H24c-C24-H24b Cll-K-Cl2 Cll-K-01 Cll-K-02 Cl2-K-01 K-Cll-Y K-Cl2-Y C28-01-C25 C26-C25-01 H25a-C25-01 H25b-C25-01 H25a-C25-C26 H25b-C25-C26 H25b-C25-H25a C27-C26-C25 H26a-C26-C25 H26b-C26-C25 H26a-C26-C27 H26b-C26-C27 H26b-C26-H26a C28-C27-C26 H27a-C27-C26 H27b-C27-C26 H27a-C27-C28 H27b-C27-C28 H27b-C27-H27a C27-C28-01 H28a-C28-01 H28b-C28-01 H28a-C28-C27 H28b-C28-C27 H28b-C28-H28a C32-02-C29 C30A-C29-02 C30B-C29-02 H29a-C29-02 H29b-C29-02 H29c-C29-02 H29d -C29-02 109.5 109.5 109.5 109.5 74.19(6) 132.0(2) 130.4(1) 87.5(1) 95.26(6) 94.81(6) 116.1(8) 96(1) 112.6 112.6 112.6 112.6 109.5 107(2) 110.1 110.1 110.1 110.1 109.5 103(1) 111.1 111 .1 111.1 111 .1 109.5 96(1) 112.7 112.7 112.7 112.7 109.5 108.7(8) 107(1) 109(1) 110.0 110.0 109.5 109.5 H29a-C29-C30A H29b-C29-C30A H29c-C29-C30B H29d -C29-C30B H29b-C29-H29a H29d -C29-H29c C31A-C30A-C29 H 30a-C30A-C29 H30b-C30A-C29 H30a-C30A-C31A H 30b-C30A-C31A H30b-C30A-H30a C32-C31A-C30A H31a-C31A-C30A H31b-C31A-C30A H31a-C31A-C32 H 31b-C31A-C32 H 31b-C31A-H31a H30c-C30B-C29 H 30d-C30B-C29 H30d-C30B-H30c C31 B-C30B-C29 H 30c-C30B-C31B H30d-C30B-C31B C32-C31 B-C30B H31c-C31B-C32 H 31d-C31B-C32 H31d-C31B-H31c H31c-C31B-C30B H31d-C31B-C30B C31A-C32-02 C31B-C32-02 H32a-C32-02 H32b-C32-02 H 32c-C32-02 H 32d-C32-02 H 32a-C32-C31A H32b-C32-C31A H32c-C32-C31B H32d-C32-C31B H32b-C32-H 32a H32d-C32-H32c ~ CpA is the centroid of atoms C1, C2, C3, C4 and C5 b CpB is the centroid of atoms C6, C7, C8, C9 and C10 110.0 110.0 109.5 109.5 109.5 109.5 105(1) 110.5 110.5 110.5 110.5 109.5 98(1) 112.2 112.2 112.2 112.2 109.5 117.0 117.0 109.5 76(2) 117.0 117.0 92(2) 113.5 113.5 109.5 113.5 113.5 105.9(9) 103(2) 110.3 110.3 111.0 111.0 110.3 110.4 111.0 111.0 109.5 109.5 132 Table 3. Crystal Data and Structure Analysis Details for dlz2[(Me 2 Si) 2 (4-CMe 3 -C5 H 2 )(3,5-CMe 2H-C 5 H 1 )]Sc{J.1-Cl) 2 K(Et2 0) 2 • Empirical formula Formula weight Crystallization solvent Crystal shape Crystal color Crystal size C 32H 32Cl2K02ScSi2 659.72 diethyl ether I petroleum ether fragment colorless 0.19 x 0.30 x 0.67 mm Data Collection rotation Preliminary photograph(s) CAD-4 Type of diffractometer 0.71073 A MoKa Wavelength 160 K Data collection temperature Theta range for 25 reflections used 10.6 to 12.2° in lattice determination a = 12.328(5) A Unit cell dimensions b = 12.894(4) A c = 13.059(4) A 1943.3(11) A3 Volume z 2 Crystal system Space group Density (calculated) F(OOO) Theta range for data collection Index ranges triclinic PI (# 2) 1.127 glcm3 684 1.5 to 25.0° -15:::; h:::; 14,-15:::; k:::; 15, -16:::; l:::; 15 Data collection scan type Reflections collected Independent reflections omega scans 15191 7609 [Rint= 0.034] Reflections > 2cr(l) Average cr(l) I (net I) 5720 0.0499 0.519 mm-1 Absorption coefficient Absorption correction Number of standards Decay of standards a= 95.58(2) 0 13= 105.57(3t y = 100.41(3) 0 none 3 reflections measured every 60 min 1.2% 133 Structure Solution and Refinement Primary solution method direct methods Secondary solution method difference map calculated full matrix least-squares on f2 Hydrogen placement Refinement method Data I restraints I parameters Treatment of hydrogen atoms 7603 I 16 I 609 coordinates refined, U;so fixed at 120% U eq of attached atom Goodness-of-fit on p2 1.432 Final R indices [1>2cr(I), 5720 reflections] R1 = 0.0421, wR2 = 0.0731 R indices (all data) Type of weighting scheme used Weighting scheme used Max shift/ error Average shift I error Largest diff. peak and hole R1 = 0.0656, wR2 = 0.0806 sigma 2 w= 1 I <f(Fo ) -0.562 0.019 0.407 and -0.381 e-A-3 Programs Used Cell refinement Data collection Data reduction Structure solution Structure refinement CAD-4 Software (Enraf-Nonius, 1989) CAD-4 Software (Enraf-Nonius, 1989) CRYM (Duchamp, 1964) SHELXS-86 (Sheldrick, 1990) SHELXL-93 (Sheldrick, 1993) Special Refinement Details A colorless crystal was mounted on a glass fiber with Paratone-N oil. Data were collected with ro-scans. Weights ware calculated as 1/cr2 (F/ ); variances (cr2 (F 0 2 )) were derived from counting statistics plus an additional term, (0.0141) 2 ; variances of the merged data were obtained by propagation of error plus another additional term, (0.014<1> f The refinement of F2 is as always against all reflections. The weighted R-factor wR and goodness of fitS are b ased on F2 , conventional R-factors Rare based on F, with F set to zero for negative F2 • The threshold expression of F2 > 2cr(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. 134 Table 4. Bond lengths [A] and angles [0 ] for dlz2[(Me 2 Si) 2 (4-CMe3 -C5 H 2 )(3,5-CMe 2H-C 5 H 1 )]Sc{J.!-Cl} 2 K(Et2 0) 2 • Sc-CpA a Sc-CpB b Sc-C10 Sc-C6 Sc-C5 Sc-C1 Sc-Cll Sc-Cl2 Sc-C4 Sc-C2 Sc-C9 Sc-C7 K-01 K-02 K-03 K-04 K-Cll K-Cl2i K-Cl2 K-Ki Cl2-Ki Si1-C102 Si1-C101 Si1-C6 Si1-C1 Si2-C202 Si2-C5 Si2-C201 Si2-C10 C1-C2 C1-C5 C2-C3 C2-H2A C3-C4 C3-C31 C31-C32 C31-C34 C31-C33 C32-H32A C32-H32B C32-H32C C33-H33A C33-H33B C33-H33C C34-H34A 2.2351(8) 2.2820(9) 2.390(2) 2.399(3) 2.436(2) 2.438(2) 2.4488(10) 2.5070(13) 2.567(3) 2.574(2) 2.650(2) 2.679(3) 2.62(2) 2.704(4) 2.762(12) 2.952(9) 3.082(2) 3.1923(15) 3.2354(14) 4.735(2) 3.1923(15) 1.864(3) 1.866(3) 1.868(3) 1.871(3) 1.864(3) 1.865(3) 1.865(3) 1.871(3) 1.418(3) 1.446(3) 1.410(3) 0.92(2) 1.409(3) 1.520(3) 1.511(4) 1.529(4) 1.538(4) 1.01(3) 1.04(3) 0.96(4) 1.10(3) 1.11(4) 1.05(3) 1.01(4) C34-H34B C34-H34C C4-C5 C4-H4A C6-C7 C6-C10 C7-C8 C7-C71 C71-C73 C71-C72 C71-H71A C72-H72A C72-H72B C72-H72C C73-H73A C73-H73B C73-H73C C8-C9 C8-H8A C9-C10 C9-C91 C91-C93 C91-C92 C91-H91A C92-H92A C92-H92B C92-H92C C93-H93A C93-H93B C93-H93C C101-H10A C101-H10B C101-H10C C102-H10D C102-H10E C102-H10F C201-H20A C201-H20B C201-H20C C202-H20D C202-H20E C202-H20F 01-C112 01-C113 C111-C112 0.98(3) 1.00(4) 1.420(3) 0.87(2) 1.423(3) 1.472(3) 1.407(3) 1.511(3) 1.513(4) 1.534(4) 0.97(2) 0.99(3) 0.98(3) 0.96(3) 0.94(3) 0.98(3) 1.00(3) 1.400(3) 0.91(2) 1.432(3) 1.512(3) 1.529(4) 1.529(4) 0.94(2) 1.00(3) 0.95(3) 0.95(3) 0.95(3) 0.98(3) 0.93(3) 0.94(4) 0.92(4) 0.92(4) 0.98(3) 0.96(3) 0.96(3) 0.87(4) 0.91(4) 0.89(5) 0.96(3) 0.96(3) 0.95(3) 1.494(10) 1.520(9) 1.531(10) 135 C111-H111 C111-H111 C111-H 111 C112-H 112 C112-Hl12 C113-C114 C113-H113 C113-H113 C114-H114 C114-H114 C114-H114 03-C312 03-C313 C311-C312 C311-H311 C311-H311 C311-H311 C312-H312 C312-H312 C313-C314 C313-H313 C313-H313 C314-H 314 C314-H314 C314-H314 02-C212 02-C213 C211-C212 C211-H211 C211-H211 C211-H211 C212-H212 C212-H212 C213-C214 C213-H213 C213-H213 C214-H214 C214-H214 C214-H214 04-C413 04-C412 C411-C412 C411-H411 C411-H411 C411-H411 C412-H412 C412-H412 C413-C414 C413-H413 0.96 0.96 0.96 0.97 0.97 1.511(9) 0.97 0.97 0.96 0.96 0.96 1.469(8) 1.509(7) 1.519(8) 0.96 0.96 0.96 0.97 0.97 1.519(7) 0.97 0.97 0.96 0.96 0.96 1.445(6) 1.472(7) 1.529(8) 0.96 0.96 0.96 0.97 0.97 1.509(7) 0.97 0.97 0.96 0.96 0.96 1.484(8) 1.528(9) 1.547(9) 0.96 0.96 0.96 0.97 0.97 1.519(10) 0.97 C413-H 413 C414-H414 C414-H414 C414-H414 0.97 0.96 0.96 0.96 CpA-Sc-CpB C10-Sc-C6 C10-Sc-C5 C6-Sc-C5 C10-Sc-C1 C6-Sc-C1 C5-Sc-C1 C10-Sc-Cll C6-Sc-Cll C5-Sc-Cl1 C1-Sc-Cll C10-Sc-Cl2 C6-Sc-Cl2 C5-Sc-Cl2 C1-Sc-Cl2 Cl1-Sc-Cl2 C10-Sc-C4 C6-Sc-C4 C5-Sc-C4 C1-Sc-C4 Cll-Sc-C4 Cl2-Sc-C4 C10-Sc-C2 C6-Sc-C2 C5-Sc-C2 C1-Sc-C2 Cll-Sc-C2 Cl2-Sc-C2 C4-Sc-C2 C10-Sc-C9 C6-Sc-C9 C5-Sc-C9 C1-Sc-C9 Cl1-Sc-C9 Cl2-Sc-C9 C4-Sc-C9 C2-Sc-C9 C10-Sc-C7 C6-Sc-C7 C5-Sc-C7 C1-Sc-C7 Cll-Sc-C7 Cl2-Sc-C7 C4-Sc-C7 122.71(3) 35.79(8) 69.34(9) 80.26(9) 79.78(9) 69.01(9) 34.52(8) 135.96(7) 105.30(7) 139.13(6) 108.68(7) 106.84(7) 137.49(7) 108.46(7) 138.78(6) 94.52(4) 97.29(9) 113.09(9) 32.85(8) 54.45(8) 123.29(6) 84.36(7) 112.50(9) 96.32(9) 54.51(8) 32.72(8) 84.66(7) 123.10(6) 51.93(8) 32.49(8) 54.56(8) 97.45(8) 112.24(8) 119.06(6) 82.94(6) 117.02(8) 144.95(8) 54.43(8) 31.95(8) 112.20(9) 96.57(9) 81.53(6) 120.78(6) 145.04(8) 136 C2-Sc-C7 C9-Sc-C7 0 1-K-Cll 02-K-Cll 03-K-Cl1 04-K-Cl1 01-K-Cl2; 02-K-Cl2; 03-K-Cl2; 04-K-Cl2; Cll-K-Cl2; 01-K-Cl2 02-K-Cl2 03-K-Cl2 04-K-Cl2 Cll-K-Cl2 Cl2;-K-Cl2 01-K-K; 02-K-K; 03-K-K; 04-K-K; C ll-K-K; Cl2;-K-K; C l2-K-K; Sc-Cll-K Sc-Cl2-K; Sc-Cl2-K K;-Cl2-K C102-Si1-C101 C102-Sil-C6 C101-Sil-C6 C 102-Si1-C1 C 101-Si1-C1 C6-Sil-C1 C102-Sil-Sc C101-Si1-Sc C6-Si1-Sc C1-Si1-Sc C202-Si2-C5 C 202-Si2-C201 C5-Si2-C201 C202-Si2-C10 C5-Si2-C10 C201-Si2-C10 C202-Si2-Sc C5-Si2-Sc C201-Si2-Sc C10-Si2-Sc C2-C1-C5 115.34(8) 51.14(8) 109.2(3) 89.21(10) 102.7(2) 80.5(2) 106.9(3) 92.18(14) 113.9(2) 108.0(2) 142.36(3) 114.6(4) 139.90(11) 116.9(2) 144.5(2) 70.32(3) 85.12(4) 118.7(3) 123.25(15) 125.6(2) 139.9(2) 107.68(4) 42.91(2) 42.21(2) 99.58(4) 142.56(3) 94.43(4) 94.88(4) 105.8(2) 115.99(14) 114.53(14) 106.95(13) 119.3(2) 94.25(11) 103.58(11) 150.59(14) 49.38(7) 50.56(8) 108.85(14) 106.5(2) 116.29(15) 114.98(13) 94.59(11) 115.5(2) 105.05(12) 50.63(8) 148.46(14) 49.25(7) 106.7(2) C2-C1-Si1 C5-C1-Sil C2-C1-Sc C5-C1-Sc Si1-C1-Sc C3-C2-C1 C3-C2-Sc C1-C2-Sc C3-C2-H2A C1-C2-H2A Sc-C2-H2A C4-C3-C2 C4-C3-C31 C2-C3-C31 C4-C3-Sc C2-C3-Sc C31-C3-Sc C32-C31-C3 C32-C31-C34 C3-C31-C34 C32-C31-C33 C3-C31-C33 C34-C31-C33 C31-C32-H32A C31-C32-H32B H32A-C32-H32B C31-C32-H32C H32A-C32-H32C H32B-C32-H32C C31-C33-H33A C31-C33-H33B H33A-C33-H33B C31-C33-H33C H33A-C33-H33C H33B-C33-H33C C31-C34-H34A C31-C34-H34B H34A-C34-H34B C31-C34-H34C H34A-C34-H34C H34B-C34-H 34C C3-C4-C5 C3-C4-Sc C5-C4-Sc C3-C4-H4A C5-C4-H4A Sc-C4-H4A C4-C5-C1 C4-C5-Si2 124.0(2) 123.6(2) 78.94(14) 72.67(13) 93.08(10) 110.4(2) 78.80(14) 68.34(13) 125.0(15) 124.6(15) 117.8(14) 106.0(2) 127.1(2) 126.4(2) 69.88(14) 70.17(13) 130.6(2) 108.6(2) 110.1(3) 111.5(2) 108.9(3) 111.6(2) 106.1(3) 100.3(15) 108.4(19) 124.4(25) 112.1(21) 102.3(25) 108.9(28) 99.9(17) 109.8(21) 119.9(26) 111.6(17) 105.2(23) 110.0(26) 106.1(25) 108.8(17) 106.2(28) 112.4(20) 112.3(31) 110.6(26) 110.6(2) 79.09(14) 68.49(14) 128.1(15) 121.3(15) 120.2(15) 106.3(2) 126.5(2) 137 C1-C5-Si2 C4-C5-Sc C1-C5-Sc Si2-C5-Sc C7-C6-C10 C7-C6-Si1 C10-C6-Si1 C7-C6-Sc C10-C6-Sc Si1-C6-Sc C8-C7-C6 C8-C7-C71 C6-C7-C71 C8-C7-Sc C6-C7-Sc C71-C7-Sc C7-C71-C73 C7-C71-C72 C73-C71-C72 C7-C71-H71A C73-C71-H71A C72-C71-H71A C71-C72-H72A C71-C72-H72B H72A-C72-H72B C71-C72-H72C H72A-C72-H72C H72B-C72-H72C C71-C73-H73A C71-C73-H73B H73A-C73-H73B C71-C73-H73C H73A-C73-H73C H73B-C73-H73C C9-C8-C7 C9-C8-Sc C7-C8-Sc C9-C8-H8A C7-C8-H8A Sc-C8-H8A C8-C9-C10 C8-C9-C91 C10-C9-C91 C8-C9-Sc C10-C9-Sc C91-C9-Sc C9-C91-C93 C9-C91-C92 C93-C91-C92 121.6(2) 78.66(14) 72.81(13) 93.08(10) 107.4(2) 127.4(2) 122.3(2) 84.93(14) 71.77(13) 94.41(10) 107.8(2) 125.7(2) 126.4(2) 78.76(15) 63.12(13) 126.4(2) 113.0(2) 110.3(2) 109.6(2) 109.1(13) 107.2(13) 107.5(14) 108.8(15) 110.8(16) 111.6(22) 111.2(16) 107.9(22) 106.5(21) 109.2(17) 112.9(18) 110.3(24) 109.6(14) 107.4(21) 107.4(23) 110.1(2) 70.25(14) 71.39(14) 126.1(15) 123.7(16) 126.5(15) 108.3(2) 125.2(2) 126.3(2) 79.95(14) 63.71(13) 126.3(2) 112.4(2) 109.8(2) 110.5(3) C9-C91-H91A C93-C91-H91A C92-C91-H91A C91-C92-H92A C91-C92-H92B H92A-C92-H92B C91-C92-H92C H92A-C92-H92C H92B-C92-H92C C91-C93-H93A C91-C93-H93B H93A-C93-H93B C91-C93-H93C H 93A-C93-H93C H93B-C93-H93C C9-C10-C6 C9-C10-Si2 C6-C10-Si2 C9-C10-Sc C6-C10-Sc Si2-C10-Sc Si1-C101-H10A Si1-C101-H10B H10A-C101-H10B Si1-C101-H10C H10A-C101-H10C H10B-C101-H10C Si1-C102-H10D Si1-C102-H10E H10D-C102-H10E Si1-C102-H10F H10D-C102-H10F H10E-C102-H10F Si2-C201-H20A Si2-C201-H20B H20A-C201-H20B Si2-C201-H20C H20 A -C201-H20C H20B-C201-H20C Si2-C202-H20D Si2-C202-H20E H20D-C202-H20E Si2-C202-H20F H20D-C202-H20F H20E-C202-H20F C112-01-C113 C112-01-K C113-01-K C112-C111-H111 110.0(15) 107.9(15) 106.0(15) 114.0(17) 106.5(17) 113.2(25) 109.1(18) 104.2(24) 109.9(24) 114.0(19) 108.6(19) 106.6(26) 109.2(19) 110.0(26) 108.3(26) 106.4(2) 128.6(2) 122.0(2) 83.80(14) 72.44(13) 94.37(10) 111.4(21) 108.7(22) 113.4(29) 119.3(25) 103.4(30) 100.3(30) 111.0(17) 107.6(19) 108.8(25) 111.9(16) 104.5(23) 113.0(24) 111.0(27) 113.7(26) 99.6(34) 116.0(29) 103.7(36) 111.2(37) 112.5(17) 110.1(17) 107.5(23) 109.2(17) 111.1(24) 106.3(23) 91.7(12) 128.1(12) 132.4(12) 109.4(14) 138 C 112-C111-H111 H111-C 111-H111 C112-C111-H111 H111-C111-H111 H111-C111-H111 01-C112-C 111 01-C112-H112 C111-C112-H112 01-C112-H112 C111-C112-H112 H112-C112-H112 C114-C113-01 C114-C113-H113 01-C113-H113 C114-C113-H113 01-C113-H113 H113-C113-H 113 C113-C114-H114 C113-C114-H114 H114-C114-H114 C113-C114-H114 H114-C1 14-H114 H114-C114-H114 C312-03-C313 C312-03-K C313-03-K C312-C311-H311 C312-C311-H311 H311-C311-H311 C312-C311-H311 H311-C311-H311 H311-C311-H311 02-C212-H212 C211-C212-H212 H212-C212-H212 02-C213-C214 02-C213-H213 C214-C213-H213 02-C213-H213 C214-C213-H213 H213-C213-H213 C213-C214-H214 C213-C214-H214 H214-C214-H214 C213-C214-H214 H214-C214-H214 H214-C214-H214 C413-04-C412 C413-04-K 109.4(12) 109.5 109.6(13) 109.5 109.5 101.5(18) 111.3(10) 111.5(12) 111.4(9) 111.7(13) 109.4 100.5(11) 111.7(6) 111.7(9) 111.7(7) 111.7(7) 109.4 109.5(7) 109.5(7) 109.5 109.5(7) 109.5 109.5 116.5(11) 121.4(8) 109.9(7) 109.4(10) 109.6(10) 109.5 109.3(10) 109.5 109.5 110.4(4) 110.4(6) 108.6 110.9(6) 109.5(3) 109.4(5) 109.5(3) 109.5(4) 108.0 109.5(5) 109.5(5) 109.5 109.5(4) 109.5 109.5 106.4(9) 121.6(8) 03-C312-C311 03-C312-H312 C311-C312-H312 03-C312-H312 C311-C312-H312 H312-C312-H312 03-C313-C314 03-C313-H313 C314-C313-H313 03-C313-H313 C314-C313-H313 H313-C313-H313 C313-C314-H314 C313-C314-H314 H314-C314-H314 C313-C314-H314 H314-C314-H314 H314-C314-H314 C212-02-C213 C212-02-K C213-02-K C212-C211-H211 C212-C211-H211 H211-C211-H211 C212-C211-H211 H21 1-C211-H211 H211-C211-H 211 02-C212-C211 02-C212-H212 C211-C212-H212 C412-04-K C412-C411-H411 C412-C411-H411 H411-C411-H411 C412-C411-H411 H411-C411-H411 H411-C411-H411 04-C412-C411 04-C412-H412 C411-C412-H 412 04-C412-H412 C411-C412-H412 H412-C412-H412 04-C413-C414 04-C413-H413 C414-C413-H413 04-C413-H413 108.1(14) 110.1(6) 110.2(10) 110.2(7) 109.9(10) 108.4 103.2(7) 111.1(6) 111.1(5) 111 .1(6) 111.1(5) 109.1 109.5(4) 109.5(5) 109.5 109.5(5) 109.5 109.5 112.3(6) 125.0(5) 117.6(4) 109.5(5) 109.5(6) 109.5 109.5(6) 109.5 109.5 106.5(8) 110.4(4) 110.4(6) 118.0(8) 109.5(9) 109.5(13) 109.5 109.5(13) 109.5 109.5 101.1(11) 111.6(8) 111.5(13) 111.6(9) 111.5(13) 109.4 104.3(12) 110.9(5) 110.9(8) 110.9(7) 139 C414-C413-H413 H413-C413-H413 C413-C414-H414 C413-C414-H414 110.9(10) 108.9 109.5(9) 109.5(8) H414-C414-H414 C413-C414-H414 H414-C414-H414 H414-C414-H414 109.5 109.5(10) 109.5 109.5 Symmetry transformations used to generate equivalent atoms: (i), -x+ 1,-y+ 1,-z+1 a b CpA is the centroid of atoms C1, C2, C3, C4 and C5 CpB is the centroid of atoms C6, C7, C8, C9 and C10 Table 5. Crystal Data and Structure Analysis Details for dlz3Y{)l-[(Me2 Si) 2 (4-CMe 3-C 5 H 2 )(3,5-CMe2 H-C 5 H 1 )] 2 ().1-H) 2 }Y. Empirical formula Formula weight Crystallization Solvent Crystal Habit Crystal size Crystal color [C 24 H 39Si 2 Y] 2 [C 6 H 6 ] 2 [945.32][156.23] benzene-d6 square columns 0.48 x 0.22 x 0.17 mm3 colorless Data Collection Preliminary Photos Type of diffractometer Wavelength Data Collection Temperature Theta range for reflections used in lattice determination Unit cell dimensions none CAD-4 0.71073 A MoKa 85K Volume 16.6 to 20.3° a= 10.477(6) A b = 16.312(11) A c = 17.341(13) A 2861(3) A3 z 2 Crystal system Space group Density (calculated) F(OOO) Theta range for data collection Completeness to 8 = 25.00° Index ranges Data collection scan type monoclinic P21 /c 1.279 Mg/ m3 1168 1.75 to 25.0° 100.0 % -12::; h::; 12,-19::; k::; 19, 0 ::; l ::; 20 ffi scans ~= 105.12(6) 0 140 Reflections collected Independent reflections 11228 5031 [Rint= 0.031; GOFmerge= 1.11] Absorption coefficient 2.138 mm-1 Absorption correction Number of standards none 3 reflections measured every 75 min. Variation of standards within counting statistics, zero %. Structure solution and Refinement Structure solution program Primary solution method Secondary solution method Hydrogen placement Structure refinement program Refinement method Data I restraints I parameters SHELXS-97 (Sheldrick, 1990) Direct methods (See Special Refinement Details) All non-H in initial solution Difference Fourier map SHELXL-97 (Sheldrick, 1997) Full matrix least-squares on F2 Max shift/ error 5031 I o I 478 unrestrained 1.392 R1 = 0.0324, wR2 = 0.0550 R1 = 0.0525, wR2 = 0.0588 sigma w= 1 I cr2 (Fo 2 ) 0.012 Average shift/ error Largest diff. peak and hole 0.000 0.413 and -0.280 e.A-3 Treatment of hydrogen atoms Goodness-of-fit on F2 Final R indices [1>2cr(l)] R indices (all data) Type of weighting scheme used Weighting scheme used Special Refinement Details Direct methods and the Patterson method were unsuccessful at solving this structure in the true space group, P21 I c, although fragments were discernable. The structure was solved by Direct methods in space group P1 using a triclinic expansion of the data, which revealed the positions of all the non-hydrogen a toms as well as the positions of the hydride. Since Z=2 for the dimer it was clear that the molecule must sit on a center of symmetry. The dimer was translated to the center at 0,0,0 and the unique atoms were retained for refinement. All other hydrogen atoms were visible in the Fourier m ap and were included in the refinement without restraints. 2 The variances [ ~(Fo )] were derived from counting statistics plus an additional term, (0.0141) 2, and the variances of the merged data were obtained by propagation of error plus the addition of another term, (0.014<1> )2 • 141 Refinement of F 2 against ALL reflections. The weighted R-factor (wR) and goodness of fit (S) are based on F 2, conventional R-factors (R) are based on F, with F set to zero for negative F2 • The threshold expression of F2 > 2cr( F2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in d istances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. Table 6. Bond lengths [A] and angles [0 ] for dlz3Y{J..1-[(Me2 Si) 2 (4-CMe 3-C 5H 2)(3,5-CMe2H-C 5 H 1 )] 2 (f..1-H) 2 }Y. Y-Cent2 Y-Centl Y-Pln2 Y-Pln1 Y-C(9) Y-C(3) Y-C(8) Y-C(4) Y-C(2) Y-C(10) Y-C(6) Y-C(5) Y-C(7) Y-C(1) Y-H Si(1)-C(3) Si(1)-C(9)i Si(1)-C(21) Si(1 )-C(22) Si(2)-C(4)i Si(2)-C(24) Si(2)-C(8) Si(2)-C(23) C(1)-C(2) C(1)-C(5) C(1)-C(11) C(2)-C(3) C(2)-H(2) C(3)-C(4) C(4)-C(5) 2.3594(15) 2.3775(13) 2.3576(27) 2.3736(27) 2.613(3) 2.622(3) 2.626(3) 2.628(3) 2.664(3) 2.668(3) 2.676(3) 2.679(3) 2.680(3) 2.744(3) 2.11(2) 1.859(3) 1.871(3) 1.871(3) 1.872(3) 1.860(3) 1.871(3) 1.878(3) 1.879(3) 1.416(4) 1.422(4) 1.523(4) 1.415(4) 0.85(2) 1.438(3) 1.424(4) C(4)-Si(2)i C(5)-H(5) C(6)-C(10) C(6)-C(7) C(6)-H(6) C(7)-C(8) C(7)-C(18) C(8)-C(9) C(9)-C(10) C(9)-Si(1Y C(10)-C(15) C(11)-C(13) C(11)-C(14) C(11 )-C(12) C(12)-H(12A) C(12)-H(12B) C(12)-H(12C) C(13)-H(13A) C(13)-H(13B) C(13)-H(13C) C(14)-H(14A) C(14)-H(14B) C(14)-H(14C) C(15)-C(16) C(15)-C(17) C(15)-H(15) C(16)-H(16A) C(16)-H(16B) C(16)-H(16C) C(17)-H(17A) 1.860(3) 0.94(2) 1.410(4) 1.416(4) 0.89(2) 1.426(4) 1.517(3) 1.455(3) 1.422(4) 1.871(3) 1.519(4) 1.526(4) 1.528(4) 1.535(4) 1.00(3) 0.90(3) 0.98(3) 0.98(3) 0.94(3) 0.99(3) 0.96(2) 0.96(3) 0.99(3) 1.528(4) 1.529(4) 0.88(2) 0.96(3) 0.97(3) 0.95(3) 0.89(3) 142 C(17)-H(17B) C(17)-H(17C) C(18)-C(20) C(18)-C(19) C(18)-H(18) C(19)-H(19A) C(19)-H(19B) C(19)-H(19C) C(20)-H(20A) C(20)-H(20B) C(20)-H(20C) C(21)-H(21A) C(21)-H(21B) C(21)-H(21C) C(22)-H(22A) C(22)-H(22B) C(22)-H(22C) C(23)-H(23A) C(23)-H(23B) C(23)-H(23C) C(24)-H(24A) C(24)-H(24B) C(24)-H(24C) 0.97(2) 0.92(3) 1.527(4) 1.530(4) 0.95(2) 0.97(3) 0.94(2) 0.97(3) 0.89(3) 0.99(3) 0.94(3) 0.98(3) 0.98(3) 1.02(3) 0.91(3) 0.96(3) 0.88(3) 0.95(3) 0.93(3) 0.92(3) 0.93(3) 0.96(3) 0.94(3) C(61)-C(62) C(61)-C(66) C(61)-H(61) C(62)-C(63) C(62)-H(62) C(63)-C(64) C(63)-H(63) C(64)-C(65) C(64)-H(64) C(65)-C(66) C(65)-H(65) C(66)-H(66) 1.380(4) 1.380(4) 0.91(3) 1.377(4) 0.90(3) 1.383(4) 0.86(3) 1.376(4) 0.92(3) 1.378(4) 0.91(3) 0.90(3) Cent2-Y -Centl Pln2-Y-Pln1 C(9)-Y-C(3) C(9)-Y -C(8) C(3)-Y-C(8) C(9)-Y-C(4) C(3)-Y-C(4) C(8)-Y -C(4) C(9)-Y -C(2) C(3)-Y -C(2) C(8)-Y -C(2) 146.24(3) 151.7(1) 168.20(8) 32.24(8) 145.69(8) 145.98(8) 31.80(8) 168.58(8) 159.65(8) 31.03(8) 134.44(8) C( 4)-Y -C(2) C(9)-Y -C(lO) C(3)-Y -C(10) C(8)-Y-C(10) C(4)-Y-C(10) C(2)-Y-C(10) C(9)-Y-C(6) C(3)-Y-C(6) C(8)-Y-C(6) C(4)-Y-C(6) C(2)-Y-C(6) C(10)-Y -C( 6) C(9)-Y -C(5) C(3)-Y-C(5) C(8)-Y-C(5) C(4)-Y -C(5) C(2)-Y -C(5) C(10)-Y -C(5) C(6)-Y-C(5) C(9)-Y -C(7) C(3)-Y-C(7) C(8)-Y-C(7) C(4)-Y-C(7) C(2)-Y -C(7) C(10)-Y-C(7) C(6)-Y-C(7) C(5)-Y -C(7) C(9)-Y-C(1) C(3)-Y-C(1) C(8)-Y-C(1) C(4)-Y-C(1) C(2)-Y-C(1) C(10)-Y-C(1) C(6)-Y-C(1) C(5)-Y -C(1) C(7)-Y-C(1) C(9)-Y-H C(3)-Y-H C(8)-Y-H C(4)-Y-H C(2)-Y-H C(10)-Y-H C(6)-Y-H C(5)-Y-H C(7)-Y-H C(1)-Y-H C(3)-Si(1)-C(9Y C(3)-Si(1)-C(21) C(9Y-Si(1)-C(21) 51.22(8) 31.22(8) 159.28(8) 52.05(9) 134.18(9) 133.93(9) 51.27(9) 140.08(8) 51.35(9) 139.68(9) 109.08(9) 30.60(8) 134.75(8) 51.44(8) 159.41(8) 31.12(8) 50.02(9) 108.92(9) 108.58(9) 51.90(8) 134.36(8) 31.16(8) 158.97(8) 109.02(9) 51.10(8) 30.66(8) 133.29(8) 139.90(8) 51.42(8) 139.46(8) 51.37(8) 30.31(8) 108.72(9) 93.12(9) 30.36(8) 108.32(9) 92.0(6) 78.2(6) 74.0(6) 96.2(6) 96.5(6) 122.5(6) 122.8(6) 126.5(6) 93.1(6) 126.4(6) 105.27(12) 109.13(13) 117.71(13) 143 C(3)-Si(1)-C(22) C(9);-Si(1)-C(22) C(21)-Si(1)-C(22) C(4r-Si(2)-C(24) C(4Y-Si(2)-C(8) C(24)-Si(2)-C(8) C( 4);-Si(2)-C(23) C(24)-Si(2)-C(23) C(8)-Si(2)-C(23) C(2)-C(1)-C(5) C(2)-C(1)-C(11) C(5)-C(1 )-C(11) C(2)-C(1 )-Y C(5)-C(1)-Y C(11)-C(1)-Y C(3)-C(2)-C(1) C(3)-C(2)-Y C(1)-C(2)-Y C(3)-C(2)-H(2) C(1)-C(2)-H(2) Y-C(2)-H(2) C(2)-C(3)-C( 4) C(2)-C(3)-Si(1) C(4)-C(3)-Si(1) C(2)-C(3)-Y C( 4)-C(3)-Y Si(1)-C(3)-Y C(5)-C( 4)-C(3) C(5)-C(4)-Si(2Y C(3)-C(4)-Si(2Y C(5)-C(4)-Y C(3)-C(4)-Y siC2r-cc 4)-Y C(1 )-C(5)-C( 4) C(1)-C(5)-Y C( 4)-C(5)-Y C(1 )-C(5)-H(5) C(4)-C(5)-H(5) Y -C(5)-H(5) C(10)-C(6)-C(7) C(10)-C(6)-Y C(7)-C(6)-Y C(10)-C(6)-H(6) C(7)-C(6)-H(6) Y-C(6)-H(6) C(6)-C(7)-C(8) C(6)-C(7)-C(18) C(8)-C(7)-C(18) C(6)-C(7)-Y 110.11(13) 107.79(13) 106.75(14) 109.88(13) 105.75(12) 117.07(13) 109.98(12) 104.61(15) 109.52(12) 105.5(2) 127.2(2) 126.3(2) 71.73(15) 72.28(15) 129.54(17) 110.8(2) 72.83(15) 77.97(15) 126.0(17) 123.2(17) 117.5(17) 106.6(2) 129.41(19) 123.89(19) 76.15(15) 74.32(14) 117.66(11) 107.0(2) 129.6(2) 123.37(19) 76.43(15) 73.88(14) 116.23(11) 110.0(2) 77.36(15) 72.46(15) 124.2(15) 125.8(15) 118.4(15) 109.4(2) 74.38(15) 74.83(15) 126.5(15) 123.8(15) 122.2(15) 107.9(2) 126.8(2) 125.1(2) 74.51(14) C(8)-C(7)-Y C(18)-C(7)-Y C(7)-C(8)-C(9) C(7)-C(8)-Si(2) C(9)-C(8)-Si(2) C(7)-C(8)-Y C(9)-C(8)-Y Si(2)-C(8)-Y C(10)-C(9)-C(8) C(10)-C(9)-Si(1 r C(8)-C(9)-Si(1); C(10)-C(9)-Y C(8)-C(9)-Y Si(1);-C(9)-Y C( 6)-C(10)-C(9) C( 6)-C(10)-C(15) C(9)-C(10)-C(15) C(6)-C(10)-Y C(9)-C(10)-Y C(15)-C(10)-Y C(1)-C(11)-C(13) C(1)-C(11)-C(14) C(13)-C(11)-C(14) C(1)-C(11)-C(12) C(13)-C(11 )-C(12) C(14)-C(11 )-C(12) C(11)-C(12)-H(12A) C(11)-C(12)-H(12B) H(12A)-C(12)-H(12B) C(11)-C(12)-H(12C) H(12A)-C(12)-H(12C) H(12B)-C(12)-H(12C) C(11)-C(13)-H(13A) C(11)-C(13)-H(13B) H(13A)-C(13)-H(13B) C(11)-C(13)-H(13C) H(13A)-C(13)-H(13C) H (13B)-C (13)-H (13C) C(11 )-C(14)-H(14A) C(11)-C(14)-H(14B) H(14A)-C(14)-H(14B) C(11)-C(14)-H(14C) H(14A)-C(14)-H(14C) H(14B)-C(14)-H(14C) C(10)-C(15)-C(16) C(10)-C(15)-C(17) C(16)-C(15)-C(17) C(10)-C(15)-H(15) C(16)-C(15)-H(15) 72.33(14) 123.34(16) 107.1(2) 129.40(19) 123.36(19) 76.52(14) 73.36(14) 119.05(11) 107.7(2) 129.22(19) 122.70(19) 76.55(14) 74.40(14) 120.33(11) 107.9(2) 126.8(2) 125.3(2) 75.03(15) 72.24(14) 121.54(16) 111.6(2) 111.4(2) 108.9(2) 108.1(2) 108.0(2) 108.8(2) 110.1(15) 107.6(16) 109(2) 112.9(15) 107(2) 110(2) 112.1(14) 111.2(15) 109(2) 111.1(14) 105(2) 108(2) 109.2(15) 110.5(16) 107(2) 113.2(14) 107(2) 110(2) 112.5(2) 113.1(2) 110.1(2) 106.6(15) 106.1(15) 144 C(17)-C(15)-H(15) C(15)-C(16)-H(16A) C(15)-C(16)-H(16B) H(16A)-C(16)-H(16B) C(15)-C(16)-H(16C) H(16A)-C(16)-H(16C) H(16B)-C(16)-H(16C) C(15)-C(17)-H(17A) C(15)-C(17)-H(17B) H(17A)-C(17)-H(17B) C(15)-C(17)-H(17C) H(17A)-C(17)-H(17C) H(17B)-C(17)-H(17C) C(7)-C(18)-C(20) C(7)-C(18)-C(19) C(20)-C(18)-C(19) C(7)-C(18)-H(18) C(20)-C(18)-H(18) C(19)-C(18)-H(18) C(18)-C(19)-H(19A) C(18)-C(19)-H(19B) H(19A)-C(19)-H(19B) C(18)-C(19)-H(19C) H(19A)-C(19)-H(19C) H(19B)-C(19)-H(19C) C(18)-C(20)-H(20A) C(18)-C(20)-H(20B) H(20A)-C(20)-H(20B) C(18)-C(20)-H(20C) H(20A)-C(20)-H(20C) H(20B)-C(20)-H(20C) Si(1)-C(21)-H(21A) Si(1)-C(21)-H(21B) H(21A)-C(21)-H(21B) Si(1 )-C(21 )-H(21 C) H(21A)-C(21)-H(21C) H(21B)-C(21)-H(21C) 108.0(15) 111.7(15) 115.4(15) 109(2) 111.0(17) 105(2) 104(2) 112.3(18) 111.7(14) 107(2) 113.3(17) 105(2) 107(2) 113.1(2) 111.8(2) 110.5(2) 106.6(15) 107.5(15) 106.9(15) 111.0(15) 112.9(14) 103(2) 109.2(15) 112(2) 108(2) 110.0(16) 111.6(15) 107(2) 111.5(17) 110(2) 106(2) 112.3(16) 109.0(15) 110(2) 112.3(15) 109(2) 104(2) Si(1)-C(22)-H(22A) Si(1)-C(22)-H(22B) H(22A)-C(22)-H(22B) Si(1)-C(22)-H(22C) H(22A)-C(22)-H(22C) H(22B )-C (22)-H(22C) Si(2)-C(23)-H(23A) Si(2)-C(23)-H(23B) H(23A)-C(23)-H(23B) Si(2)-C(23)-H(23C) H(23A)-C(23)-H(23C) H(23B)-C(23)-H(23C) Si(2)-C(24)-H(24A) Si(2)-C(24)-H(24B) H(24A)-C(24)-H(24B) Si(2)-C(24)-H(24C) H(24A)-C(24)-H(24C) H(24B)-C(24)-H(24C) 110.2(17) 115.3(18) 104(2) 115(2) 106(2) 105(3) 111.6(17) 106.8(19) 110(2) 111.4(18) 107(2) 111(2) 105.8(17) 114.1(16) 109(2) 109.8(18) 110(2) 108(2) C(62)-C(61)-C(66) C(62)-C(61)-H(61) C(66)-C(61)-H(61) C(63)-C(62)-C(61) C(63)-C(62)-H(62) C(61)-C(62)-H(62) C(62)-C(63)-C(64) C(62)-C(63)-H(63) C(64)-C(63)-H(63) C(65)-C(64)-C(63) C(65)-C(64)-H(64) C(63)-C(64)-H( 64) C(64)-C(65)-C(66) C(64)-C(65)-H(65) C(66)-C(65)-H( 65) C(65)-C(66)-C( 61) C(65)-C(66)-H(66) C(61)-C(66)-H(66) 119.8(3) 119.3(18) 120.9(18) 120.0(3) 121.4(19) 118.6(19) 120 .2(3) 122.3(19) 117.5(19) 119.8(3) 121.6(17) 118.6(17) 120.1(3) 118.9(17) 120.9(17) 120.2(3) 116.8(17) 123.0(17) Symmetry transformations used to generate equivalent atoms: (i),-x,-y,-z Centl is the centroid formed by C1, C2, C3, C4 and C5. Cent2 is the centroid formed by C6, C7, C8, C9 and C10. Plnl is the plane formed by C1, C2, C3, C4 and C5. Pln2 is the plane formed by C6, C7, C8, C9 and C10. 145 Table 7. Crystal Data and Structure Analysis Details for dlz4[(Me 2 Si) 2 ( 4-CMe3 -C5 H 2 )(3,5-CMe2H -C 5 H 1 )] Sc{J.1-Me) 2 A1Me 2 • Empirical formula Formula weight Crystallization Solvent Crystal Habit Crystal size Crystal color Preliminary Photos Type of diffractometer Wavelength Data Collection Temperature Theta range for reflections used in lattice determination Unit cell dimensions Volume z Crystal system Space group Density (calculated) F(OOO) Theta range for data collection Completeness toe= 25.00° Index ranges Data collection scan type Reflections collected Independent reflections Absorption coefficient Absorption correction Number of standards Variation of standards C 28 H 50AlScSi2 514.80 toluene fragment 0.41 x 0.28 x 0.09 mm3 colorless Data Collection none CAD-4 0.71073 A MoKa 85K 10.9 to 16.8° a = 10.960(3) A a= 96.39(4) 0 b = 11.033(5) A 13= 104.22(4) 0 c = 12.835(8) A y = 94.01(3) 0 1487.5(12) A3 2 triclinic PI 1.149 mg / m3 560 1.65 to 25.0° 100.0 % -13::; h::; 12,-13 ::; k::; 13, -15::; 1::; 14 m scans 11200 5212 [Rint= 0.021; GOFmerge= 1.06 ] 0.371 mm-1 none 3 reflections measured every 75 min. within counting statistics, zero %. Structure solution and Refinement SHELXS-97 (Sheldrick, 1990) Structure solution program 146 Primary solution method Secondary solution method Hydrogen placement Structure refinement program Refinement method Data I restraints I parameters Treatment of hydrogen atoms Goodness-of-fit on F2 Final R indices [I> 2cr(I)] Direct methods All heavy atoms in initial solution Difference Fourier map SHELXL-97 (Sheldrick, 1997) Full matrix least-squares on F2 5212 I o I 489 unrestrained 1.725 R1 = 0.0305, wR2 = 0.0646 R indices (all data) Type of weighting scheme used Weighting scheme used R1 = 0.0387, wR2 = 0.0664 sigma w= 1 I [cr2 (Fo 2 ) Max shift I error Average shift/error Largest diff. peak and hole 0.001 0.000 0.336 and -0.213 e .A -3 Special Refinement Details Inspection of the structural geometry and the bond distances would suggest that the methyl groups (C25, C26, C27 & C28) are bonded to the aluminum atom. Methyl groups C(25) and C(26), those closest to scandium, are approximately 0.4A further from the scandium than would be expected for a Se-C single bond to an alkyl (See Table 3, Figures 5 and 6). This would suggest they are not strongly bond to scandium. However, the hydrogen atoms H(25C) and H(26C) are at a distance from scandium that would suggest a bonding interaction (See Table 3, Figures 5 and 6). The variances [ cr2 (Fo 2 )] were derived from counting statistics plus an additional term, (0.0141) 2 , and the variances of the merged data were obtained by propagation of error plus the addition of another term, (0.014<1> f Refinement of F 2 against ALL reflections. The weighted R-factor (wR) and goodness of fit (S) are based on F 2, conventional R-factors (R) are based on F, with F set to zero for negative F2 • The threshold expression of F 2 > 2cr( F2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined 147 by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. Table 8. Selected bond lengths [A] and angles [0 ] for dlz4[(Me 2 Si) 2 (4-CMe 3 -C 5H 2)(3,5-CMe2 H-C5 H 1 )]Sc{J..L-Me) 2 AlMe 2 • Pln1-Sc Pln2-Sc 2.213(1) 2.195(1) Centl-Sc Cent2-Sc 2.239(1) 2.233(1) Se-Al Sc-C(26) Sc-C(25) Sc-H(26C) Sc-H(25C) 2.9179(14) 2.414(2) 2.442(2) 2.21(2) 2.19(2) Al-C(27) Al-C(28) Al-C(25) Al-C(26) 1.971(2) 1.970(2) 2.081(2) 2.087(2) Angles around Sc Pln1-Sc-Pln2 Centl-Sc-Cent2 C(26)-Sc-C(25) H(25C)-Sc-H(26C) Angles around AI 104.32(7) 123.53(3) 88.48(8) 131.4(9) C(27)-Al-C(28) C(27)-Al-C(25) C(28)-Al-C(25) C(27)-Al-C(26) C(28)-Al-C(26) C(25)-Al-C(26) 111.13(10) 109.69(10) 110.14(9) 113.52(10) 103.45(10) 108.73(9) Angles around C(25) Al-C(25)-Sc 79.92(7) Al-C(25)-H(25A) Al-C(25)-H(25B) Al-C(25)-H(25C) 112(1) 90(1) 134(1) Sc-C(25)-H(25A) Sc-C(25)-H(25B) Sc-C(25)-H(25C) 107(1) 146(2) 63(2) Angles around C(26) Al-C(26)-Sc 80.47(7) Al-C(26)-H(26A) Al-C(26)-H(26B) Al-C(26)-H(26C) 108(1) 90(1) 139(1) Sc-C(26)-H(26A) Sc-C(26)-H(26B) Sc-C(26)-H(26C) Centl is the centroid formed by C1, C2, C3, C4 and C5. Cent2 is the centroid formed by C6, C7, C8, C9 and C10. Pln1 is the plane formed by C1, C2, C3, C4 and C5. Pln2 is the plane formed by C6, C7, C8, C9 and C10. 106(1) 145(1) 67(1) 148 Table 9. Bond lengths [A] and angles [0 ] for dlz4[(Me 2 Si) 2 (4-CMe3 -C5 H 2 )(3,5-CMe2 H-C 5 H 1 )]Sc(!-l-Me)2 AlMe 2 • Pln1-Sc Pln2-Sc Centl-Sc Cent2-Sc Sc-C(9) Sc-C(8) Sc-C(26) Sc-C(3) Sc-C(4) Sc-C(25) Sc-C(2) Sc-C(5) Sc-C(10) Sc-C(7) Sc-C(6) Sc-C(1) Si(1 )-C(22) Si(1)-C(3) Si(1)-C(21) Si(1)-C(8) Si(2)-C(23) Si(2)-C(24) Si(2)-C(4) Si(2)-C(9) Al-C(27) Al-C(28) Al-C(25) Al-C(26) C(1)-C(5) C(1)-C(2) C(1)-C(ll) C(2)-C(3) C(2)-H(2) C(3)-C(4) C(4)-C(5) C(5)-H(5) C(6)-C(7) C(6)-C(10) C(6)-H(6) C(7)-C(8) C(7)-C(15) C(8)-C(9) C(9)-C(10) C(10)-C(18) C(ll)-C(14) C(11)-C(13) 2.2134(1) 2.1950(14) 2.2387(1) 2.2331(10) 2.3759(18) 2.381(2) 2.414(2) 2.417(2) 2.423(2) 2.442(2) 2.575(2) 2.583(2) 2.6117(19) 2.619(2) 2.704(2) 2.715(2) 1.862(2) 1.864(2) 1.872(2) 1.882(2) 1.852(2) 1.866(2) 1.8729(19) 1.878(2) 1.971(2) 1.970(2) 2.081(2) 2.087(2) 1.414(2) 1.416(3) 1.528(2) 1.424(2) 0.969(19) 1.443(3) 1.420(3) 0.898(18) 1.407(3) 1.410(3) 0.903(18) 1.430(3) 1.519(3) 1.471(2) 1.419(2) 1.521(3) 1.517(3) 1.521(3) C(ll)-C(12) C(12)-H(12A) C(12)-H(12B) C(12)-H(12C) C(13)-H(13A) C(13)-H(13B) C(13)-H(13C) C(14)-H(14A) C(14)-H(14B) C(14)-H(14C) C (15)-C (17) C(15)-C(16) C(15)-H(15) C(16)-H(16A) C(16)-H(16B) C(16)-H(16C) C(17)-H(17A) C(17)-H(17B) C(17)-H(17C) C(18)-C(20) C(18)-C(19) C(18)-H(18) C(19)-H(19A) C(19)-H(19B) C (19)-H(19C) C(20)-H(20A) C(20)-H(20B) C(20)-H(20C) C(21)-H(21A) C(21)-H(21B) C(21)-H(21C) C(22)-H(22A) C(22)-H(22B) C(22)-H(22C) C (23)-H(23A) C(23)-H(23B) C(23)-H(23C) C(24)-H(24A) C(24)-H(24B) C(24)-H(24C) C(25)-H(25A) C(25)-H(25B) C(25)-H(25C) C(26)-H(26A) C(26)-H(26B) C(26)-H(26C) 1.530(3) 0.96(2) 0.96(3) 0.91(2) 0.98(2) 0.94(2) 0.96(2) 0.97(3) 1.02(3) 0.96(2) 1.522(3) 1.530(3) 0.977(18) 0.94(2) 0.99(2) 0.98(2) 0.96(2) 0.94(2) 0.92(2) 1.523(3) 1.530(3) 0.971(18) 0.96(2) 0.96(2) 0.95(2) 0.92(2) 0.95(2) 0.97(2) 1.01(2) 0.94(2) 0.93(2) 0.89(3) 0.94(3) 0.92(3) 0.95(3) 0.93(2) 0.89(2) 0.95(2) 0.96(2) 0.95(2) 0.99(2) 0.84(3) 0.92(3) 1.00(2) 0.93(2) 0.98(2) 149 C(27)-H(27A) C(27)-H(27B) C(27)-H(27C) C(28)-H(28A) C(28)-H(28B) C(28)-H(28C) 0.90(3) 0.87(3) 0.85(3) 0.95(2) 0.93(3) 0.93(3) Pln1-Sc-Pln2 Centl-Sc-Cent2 C(9)-Sc-C(8) C(9)-Sc-C(26) C(8)-Sc-C(26) C(9)-Sc-C(3) C(8)-Sc-C(3) C(26)-Sc-C(3) C(9)-Sc-C(4) C(8)-Sc-C(4) C(26)-Sc-C(4) C(3)-Sc-C(4) C(9)-Sc-C(25) C(8)-Sc-C(25) C(26)-Sc-C(25) C(3)-Sc-C(25) C(4)-Sc-C(25) C(9)-Sc-C(2) C(8)-Sc-C(2) C(26)-Sc-C(2) C(3)-Sc-C(2) C(4)-Sc-C(2) C(25)-Sc-C(2) C(9)-Sc-C(5) C(8)-Sc-C(5) C(26)-Sc-C(5) C(3)-Sc-C(5) C(4)-Sc-C(5) C(25)-Sc-C(5) C(2)-Sc-C(5) C(9)-Sc-C(10) C(8)-Sc-C(10) C(26)-Sc-C(10) C(3)-Sc-C(10) C(4)-Sc-C(10) C(25)-Sc-C(10) C(2)-Sc-C(10) C(5)-Sc-C(10) C(9)-Sc-C(7) C(8)-Sc-C(7) C(26)-Sc-C(7) C(3)-Sc-C(7) 104.32(7) 123.53(3) 36.02(6) 107.45(7) 138.07(7) 80.79(7) 69.51(7) 139.32(7) 69.24(7) 79.88(7) 109.71(7) 34.68(6) 139.82(7) 110.22(8) 88.48(8) 111.03(7) 140.31(7) 113.73(7) 97.55(7) 121.74(7) 32.95(6) 54.74(6) 85.61(7) 96.55(7) 112.65(7) 84.78(7) 54.55(7) 32.77(6) 121.98(7) 52.00(7) 32.63(6) 55.33(6) 82.76(7) 113.41(6) 97.33(7) 120.34(7) 146.36(6) 115.77(7) 55.27(7) 32.79(6) 120.28(7) 97.50(7) C(4)-Sc-C(7) C(25)-Sc-C(7) C(2)-Sc-C(7) C(5)-Sc-C(7) C(10)-Sc-C(7) C(9)-Sc-C(6) C(8)-Sc-C(6) C(26)-Sc-C(6) C(3)-Sc-C(6) C(4)-Sc-C(6) C(25)-Sc-C(6) C(2)-Sc-C(6) C(5)-Sc-C(6) C(10)-Sc-C(6) C(7)-Sc-C(6) C(9)-Sc-C(1) C(8)-Sc-C(1) C(26)-Sc-C(1) C(3)-Sc-C(1) C(4)-Sc-C(1) C(25)-Sc-C(1) C(2)-Sc-C(1) C(5)-Sc-C(1) C(10)-Sc-C(1) C(7)-Sc-C(1) C(6)-Sc-C(1) C(9)-Sc-H(25C) C(8)-Sc-H(25C) C(26)-Sc-H(25C) C(3)-Sc-H(25C) C(4)-Sc-H(25C) C(25)-Sc-H(25C) C(2)-Sc-H(25C) C(5)-Sc-H(25C) C(10)-Sc-H(25C) C(7)-Sc-H(25C) C(6)-Sc-H(25C) C(1)-Sc-H(25C) C(9)-Sc-H(26C) C(8)-Sc-H(26C) C(26)-Sc-H(26C) C(3)-Sc-H(26C) C(4)-Sc-H(26C) C(25)-Sc-H(26C) C(2)-Sc-H(26C) C(5)-Sc-H(26C) C(10)-Sc-H(26C) C(7)-Sc-H(26C) C(6)-Sc-H(26C) 112.66(7) 84.72(7) 116.74(7) 145.43(6) 52.21(6) 53.17(6) 53.27(6) 90.67(7) 122.77(6) 122.38(7) 91.13(7) 147.25(6) 146.33(6) 30.70(6) 30.61(6) 122.75(6) 123.04(6) 91.87(7) 53.54(6) 53.51(6) 92.31(7) 30.90(6) 30.83(6) 146.57(6) 147.53(6) 175.78(5) 122.7(7) 89.4(7) 109.6(7) 97.3(7) 131.4(7) 22.2(7) 80.5(7) 128.6(7) 114.9(7) 68.6(7) 84.3(7) 98.0(7) 85.3(6) 119.6(5) 23.9(5) 128.1(5) 93.8(5) 111.6(5) 127.0(5) 78.1(5) 66.4(5) 114.6(5) 84.4(5) 150 C(1)-Sc-H(26C) H(25C)-Sc-H(26C) C(22)-Si(1)-C(3) C(22)-Si(1)-C(21) C(3)-Si(1)-C(21) C(22)-Si(1)-C(8) C(3)-Si(1)-C(8) C(21)-Si(1)-C(8) C(22)-Si(1)-Sc C(3)-Si(1 )-Sc C(21)-Si(1)-Sc C(8)-Si(1)-Sc C(23)-Si(2)-C(24) C(23)-Si(2)-C( 4) C(24)-Si(2)-C( 4) C(23)-Si(2)-C(9) C(24)-Si(2)-C(9) C( 4)-Si(2)-C(9) C(23)-Si(2)-Sc C(24)-Si(2)-Sc C( 4)-Si(2)-Sc C(9)-Si(2)-Sc C(27)-Al-C(28) C(27)-Al-C(25) C(28)-Al-C(25) C(27)-Al-C(26) C(28)-Al-C(26) C(25)-Al-C(26) C(27)-Al-Sc C(28)-Al-Sc C(25)-Al-Sc C(26)-Al-Sc C(5)-C(1 )-C(2) C(5)-C(1 )-C(11) C(2)-C(1)-C(11) C(5)-C(1)-Sc C(2)-C(1)-Sc C(11)-C(1)-Sc C(1 )-C(2)-C(3) C(1)-C(2)-Sc C(3)-C(2)-Sc C(1)-C(2)-H(2) C(3)-C(2)-H(2) Sc-C(2)-H(2) C(2)-C(3)-C(4) C(2)-C(3)-Si(1) C(4)-C(3)-Si(1) C(2)-C(3)-Sc C (4)-C(3)-Sc 96.6(5) 131.4(9) 114.79(10) 107.25(11) 108.98(10) 116.43(10) 93.83(9) 115.12(10) 146.90(8) 49.92(6) 105.74(8) 48.85(6) 105.99(10) 120.56(9) 106.91(9) 114.15(9) 116.00(9) 93.26(8) 149.60(7) 104.36(8) 49.91(6) 48.48(6) 111.13(10) 109.69(10) 110.14(9) 113.52(10) 103.45(10) 108.73(9) 118.51(8) 130.29(7) 55.47(6) 54.67(6) 106.06(16) 126.35(16) 126.50(16) 69.41(10) 69.05(10) 135.25(12) 110.09(16) 80.05(11) 67.44(10) 124.5(11) 125.4(11) 121.3(11) 106.80(15) 127.13(14) 121.31(13) 79.60(11) 72.87(10) Si(1)-C(3)-Sc C(5)-C(4)-C(3) C(5)-C(4)-Si(2) C(3)-C(4)-Si(2) C(5)-C(4)-Sc C(3)-C(4)-Sc Si(2)-C( 4)-Sc C(1)-C(5)-C(4) C(1)-C(5)-Sc C(4)-C(5)-Sc C(1 )-C(5)-H(5) C(4)-C(5)-H(5) Sc-C(5)-H(5) C(7)-C(6)-C(10) C(7)-C(6)-Sc C(10)-C(6)-Sc C(7)-C(6)-H(6) C(10)-C(6)-H(6) Sc-C(6)-H(6) C(6)-C(7)-C(8) C(6)-C(7)-C(15) C(8)-C(7)-C(15) C(6)-C(7)-Sc C(8)-C(7)-Sc C(15)-C(7)-Sc C(7)-C(8)-C(9) C(7)-C(8)-Si(1) C(9)-C(8)-Si(1) C(7)-C(8)-Sc C(9)-C(8)-Sc Si(1 )-C(8)-Sc C(10)-C(9)-C(8) C(10)-C(9)-Si(2) C(8)-C(9)-Si(2) C(10)-C(9)-Sc C(8)-C(9)-Sc Si(2)-C(9)-Sc C(6)-C(10)-C(9) C(6)-C(10)-C(18) C(9)-C(10)-C(18) C(6)-C(10)-Sc C(9)-C(10)-Sc C(18)-C(10)-Sc C(14)-C(11)-C(13) C(14)-C(11)-C(1) C(13)-C(11)-C(1) C(14)-C(11)-C(12) C(13)-C(11)-C (12) C(1 )-C(11 )-C(12) 93.92(8) 106.63(15) 124.80(13) 123.62(13) 79.82(11) 72.45(10) 93.83(8) 110.41(16) 79.76(11) 67.41(10) 125.2(11) 124.4(11) 119.5(11) 109.59(16) 71.38(10) 71.05(10) 125.4(12) 124.9(12) 127.4(11) 108.16(16) 125.34(16) 126.10(16) 78.01(11) 64.41(10) 128.63(12) 106.68(15) 127.79(13) 122.00(13) 82.80(11) 71.80(10) 94.64(8) 107.23(15) 128.14(13) 121.48(13) 82.86(10) 72.18(10) 95.23(8) 108.23(16) 126.01(16) 125.44(16) 78.25(11) 64.51(9) 127.67(12) 108.91(18) 111.47(16) 111.52(16) 108.89(19) 108.18(19) 107.78(16) 151 C(11)-C(12)-H(12A) C(11)-C(12)-H(12B) H(12A)-C(12)-H(12B) C(11 )-C(12)-H(12C) H(12A)-C(12)-H(12C) H(12B)-C(12)-H(12C) C(11)-C(13)-H(13A) C(11 )-C (13 )-H(13B) H(13A)-C(13)-H(13B) C(11)-C(13)-H(13C) H(13A)-C(13)-H(13C) H(13B)-C(13)-H(13C) C(11)-C(14)-H(14A) C(11)-C(14)-H(14B) H(14A)-C(14)-H(14B) C(11)-C(14)-H(14C) H(14A)-C(14)-H(14C) H(14B)-C(14)-H(14C) C(7)-C(15)-C(17) C(7)-C(15)-C(16) C(17)-C(15)-C(16) C(7)-C(15)-H(15) C(17)-C(15)-H(15) C(16)-C(15)-H(15) C(15)-C(16)-H(16A) C(15)-C(16)-H(16B) H(16A)-C(16)-H(16B) C(15)-C(16)-H(16C) H(16A)-C(16)-H(16C) H(16B)-C(16)-H(16C) C(15)-C(17)-H(17A) C(15)-C(17)-H(17B) H(17A)-C(17)-H(17B) C(15)-C(17)-H(17C) H(17A)-C(17)-H(17C) H(17B)-C(17)-H(17C) C(10)-C(18)-C(20) C(10)-C(18)-C(19) C(20)-C(18)-C(19) C(10)-C(18)-H(18) C(20)-C(18)-H(18) C(19)-C(18)-H(18) C(18)-C(19)-H(19 A) C(18)-C(19)-H(19B) H(19A)-C(19)-H(19B) C(18)-C(19)-H(19C) H(19A)-C(19)-H(19C) H(19B)-C(19)-H(19C) C(18)-C(20)-H(20A) 109.9(13) 111.7(15) 111(2) 108.9(14) 108.3(19) 107(2) 111.1(13) 111.5(14) 106.7(19) 109.2(12) 110.3(18) 108.1(18) 111.1(14) 112.7(14) 107(2) 109.3(13) 108.8(19) 107.9(19) 112.87(16) 109.13(16) 109.76(17) 110.1(11) 107.3(11) 107.5(11) 111.7(12) 110.3(13) 106.3(17) 108.5(13) 111.1(18) 108.9(18) 109.7(12) 112.4(12) 107.9(16) 110.6(13) 107.6(17) 108.5(17) 113.11(16) 109.39(15) 109.71(16) 107.7(11) 108.2(10) 108.6(10) 109.2(12) 111.1(12) 106.6(17) 110.4(12) 108.5(16) 111.0(17) 111.3(12) C(18)-C(20)-H(20B) H(20A)-C (20)-H(20B) C(18)-C(20)-H(20C) H(20A)-C(20)-H(20C) H(20B)-C(20)-H(20C) Si(1)-C(21)-H(21A) Si(1)-C(21)-H(21B) H(21A)-C(21)-H(21B) Si(1 )-C(21 )-H (21 C) H(21A)-C(21 )-H(21 C) H(21B)-C(21)-H(21C) Si(1)-C(22)-H(22A) Si(1 )-C(22)-H(22B) H(22A)-C(22)-H(22B) Si(1)-C(22)-H(22C) H(22A)-C(22)-H(22C) H(22B)-C(22)-H(22C) Si(2)-C(23)-H(23A) Si(2)-C(23)-H(23B) H(23A)-C(23)-H(23B) Si(2)-C(23)-H(23C) H(23A)-C(23)-H(23C) H(23B)-C(23)-H(23C) Si(2)-C(24)-H(24A) Si(2)-C(24)-H(24B) H(24A)-C(24)-H(24B) Si(2)-C(24)-H(24C) H(24A)-C(24)-H(24C) H(24B)-C(24)-H(24C) Al-C(25)-Sc A l-C(25)-H(25A) Sc-C(25)-H(25A) Al-C(25)-H(25B) Sc-C(25)-H(25B) H(25A)-C(25)-H(25B) A l-C(25)-H(25C) Sc-C(25)-H(25C) H(25A)-C(25)-H(25C) H(25B)-C(25)-H(25C) Al-C(26)-Sc Al-C(26)-H(26A) Sc-C(26)-H(26A) Al-C(26)-H(26B) Sc-C(26)-H(26B) H(26A)-C(26)-H(26B) Al-C(26)-H(26C) Sc-C(26)-H(26C) H(26A)-C(26)-H(26C) H(26B)-C(26)-H(26C) 111.5(12) 104.6(16) 113.3(12) 103.9(16) 111.7(16) 113.4(11) 110.3(13) 108.1(16) 106.2(14) 107.9(17) 110.9(19) 108.3(16) 109.4(14) 111(2) 113.2(16) 109(2) 106(2) 113.7(14) 113.7(13) 109.0(19) 106.4(15) 105(2) 108.6(19) 110.2(12) 114.6(12) 107.8(17) 106.8(14) 110.3(18) 107.0(18) 79.92(7) 111.8(13) 106.6(13) 90.6(17) 145.9(17) 107(2) 134.1(16) 63.3(15) 105(2) 105(2) 80.47(7) 107.9(11) 106.3(12) 90.2(12) 145.1(12) 108.6(17) 139.0(12) 66.6(12) 104.4(16) 102.8(17) 152 Al-C(27)-H(27A) Al-C(27)-H(27B) H(27A)-C(27)-H(27B) Al-C(27)-H(27C) H(27A)-C(27)-H(27C) H(27B)-C(27)-H(27C) 117(2) 114(2) 100(3) 113(2) 102(3) 109(3) Al-C(28)-H(28A) Al-C(28)-H(28B) H(28A)-C(28)-H(28B) Al-C(28)-H(28C) H(28A)-C(28)-H(28C) H(28B)-C(28)-H(28C) 112.4(13) 109.8(15) 103.8(19) 115.5(16) 108(2) 107(2) Centl is the centroid formed by C1, C2, C3, C4 and C5. Cent2 is the centroid formed by C6, C7, C8, C9 and C10. Pln1 is the plane formed by C1, C2, C3, C4 and C5. Pln2 is the plane formed by C6, C7, C8, C9 and C10. Table 10. Crystal Data and Structure Analysis Details for dlzS[(Me2 Si) 2 (4-CMe3 -C5 H 2 )(3,5-CMe2 H-C 5H 1 )]YCH(SiMe3 ) 2 • Empirical formula Formula weight Crystallization solvent Crystal shape Crystal color Crystal size C31Hs7Si4Y 631.04 toluene-d8 six-sided plate colorless 0.22 x 0.37 x 0.37 mm Data Collection Type of diffractometer Wavelength Data collection temperature Theta range for 25 reflections used in lattice determination Unit cell dimensions CAD-4 0.71073 A MoKa 84K Volume 13 to 15° a= 16.262(4) A b = 11.833(6) A c = 17.978(9) A 3455(3) A3 z 4 Crystal system Space group Density (calculated) monoclinic P21 / n (#14) 1.213 g / cm3 1352 1.5 to 25.0° 100.0 % -15::; h::; 19,-14::; k::; 14,-21::; 1::; 21 F(OOO) Theta range for data collection Completeness to theta = 25.0° Index ranges a= 90° 0 ~= 92.94(3) y = 90° 153 Data collection scan type ro-scan 20178 6067 [Rint= 0.057; GOFmerge= 1.07] Reflections collected Independent reflections 4766 0.0533 1.845 mm-1 Reflections > 2cr(I) Average cr(I) I (net I) Absorption coefficient Absorption correction Max. and min. transmission Number of standards \jl-scan 1.08 and 0.91 3 reflections measured every 75 min 0.6% Decay of standards Structure Solution and Refinement Primary solution method Secondary solution method Hydrogen placement Refinement method Data I restraints I parameters Treatment of hydrogen atoms direct methods difference map calculated full-matrix least-squares on p2 6067 I o I 492 coordinates refined, U ;so fixed at 120% Ueq of attached atom Goodness-of-fit on p2 1.456 Final R indices [I>2cr(I), 4766 reflections] R1 = 0.0416, wR2 = 0.0598 R indices (all data) Type of weighting scheme used Weighting scheme used Max shift I error Average shift/ error Largest diff. peak and hole R1 = 0.0665, wR2 = 0.0640 sigma w= 1 I if(Fo2 ) 0.032 0.001 0.406 and -0.390 e-A-3 Programs Used Cell refinement Data collection Data reduction Structure solution Structure refinement CAD-4 Software (Enraf-Nonius, 1989) CAD-4 Software (Enraf-Nonius, 1989) CRYM (Duchamp, 1964) Bruker SHELXTL v5.1 Bruker SHELXTL v5.1 154 Special Refinement Details A small colorless six-sided plate was mounted on a glass fiber with Paratone-N oil. Data were collected with 1.0° ro-scans. Data that agreed poorly in a preliminary merging were recollected. The individual backgrounds were replaced by a background function of 28 derived from those reflections with I < 3cr(l). The GOFmerge was 1.07 (6067 multiples) in point group 2/m; Rmerge was 0.061 for 2233 duplicates with F0 > 0. \f'-scan data were used for the absorption correction. There was 0.6% linear decay. No outlier reflections were omitted from the refinement. A power failure occurred during the collection of reflection number 17290, shutting down the diffractometer and cooling unit; however, this event seems to have had no significant effect on the crystal or data set quality. Weights ware calculated as 1 / cr2 (F0 2 ); variances (cr2(F0 2 )) were derived from counting statistics plus an additional term, (0.0141?; variances of the merged data were obtained by propagation of error plus another additional term, (0.014<1> )2 • The refinement of F 2 is as always against all reflections. The weighted R-factor wR and goodness of fitS are based on F2 , conventional R-factors Rare based on F, with F set to zero for negative F 2 • The threshold expression of F 2 > 2cr(F 2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. There is one molecule in the asymmetric unit. During refinement two atoms, C25 and C26, exhibited elongated displacement ellipsoids indicating disorder. The central carbon of the CH(SiMe 3 ) 2 moiety, C25, exists in either of two conformations, with the H up or with the H down with respect to the wedge of the cyclopentadienyl rings. The inversion of the carbon primarily affects C26, a terminal methyl group, which can also be correspondingly down or up . Various models were tried which attempted to split both atoms into two sites each, ~0 .6A apart. None were very s u ccessful. The final model leaves the methyl carbon C26 as a single anisotropic atom and C25 split into C25A with a population of 0.719(11) with the hydrogen atom pointed towards the t-butyl group and C25B with a population of 0.281(11). Both partial atoms were refined isotropically with a single U iso· A more interesting feature of the structure is the interaction between theY atom and a Si-C bond (Si4-C29). The disordered coordinated carbon C25 of the CH(SiMe3) 2 moiety is shifted to one side of the wedge to allow the Si-C bond access to theY atom. Table 11. Bond lengths [A] and angles [ 0 ] for dlz5[(Me 2 Si) 2 (4-CMe3 -C5 H 2 )(3,5-CMe2 H-C 5 H 1 )]YCH(SiMe3 ) 2 • Y-CpA a Y-CpB c Y-Cen e 2.394 2.386 2.806 Y.· ·PlnA b Y.··PlnB ct Y-C6 2.371(2) 2.356(2) 2.534(3) 155 Y-C7 Y-C1 Y-C2 Y-C4 Y-C5 Y-C3 Y-C10 Y-C8 Y-C9 Y-C25B Y-C25A Y-C29 Y. ··Si4 Y. ··H29C Si1-C11 Si1-C12 Si1-C1 Si1-C6 Si2-C13 Si2-C14 Si2-C2 Si2-C7 Si3-C25A Si3-C27 Si3-C26 Si3-C28 Si3-C25B Si4-C25A Si4-C31 Si4-C30 Si4-C25B Si4-C29 C1-C5 C1-C2 C2-C3 C3-C4 C3-H3 C4-C5 C4-C15 C5-H5 C6-C10 C6-C7 C7-C8 C8-C9 C8-C19 C9-C10 C9-H9 C10-C22 Cll-HllA 2.535(3) 2.549(3) 2.591(3) 2.842(3) 2.681(3) 2.737(3) 2.742(3) 2.743(3) 2.821(3) 2.377(10) 2.437(4) 2.751(4) 3.1673(16) 2.58(3) 1.859(3) 1.864(3) 1.869(3) 1.889(3) 1.847(3) 1.862(3) 1.874(3) 1.878(3) 1.859(4) 1.860(4) 1.865(4) 1.876(4) 1.888(11) 1.828(4) 1.858(4) 1.860(4) 1.882(11) 1.922(3) 1.429(4) 1.440(4) 1.419(4) 1.415(4) 0.90(3) 1.405(4) 1.521(4) 0.91(3) 1.437(4) 1.457(4) 1.424(4) 1.414(4) 1.518(4) 1.408(4) 0.91(3) 1.514(4) 0.91(3) C11-H11B C11-H11C C12-H12A C12-H12B C12-H12C C13-H13A C13-H13B C13-H13C C14-H14A C14-H14B C14-H14C C15-C16 C15-C18 C15-C17 C16-H16A C16-H16B C16-H16C C17-H17A C17-H17B C17-H17C C18-H18A C18-H18B C18-H18C C19-C21 C19-C20 C19-H19A C20-H20A C20-H20B C20-H20C C21-H21A C21-H21B C21-H21C C22-C24 C22-C23 C22-H22 C23-H23A C23-H23B C23-H23C C24-H24A C24-H24B C24-H24C C25A···C25B C25A-H25A C25B-H25B C26-H26A C26-H26B C26-H26C C27-H27A C27-H27B 0.94(3) 0.95(3) 0.94(3) 0.95(3) 0.95(3) 0.98(3) 0.91(3) 0.83(3) 0.97(3) 0.92(3) 0.89(3) 1.518(4) 1.523(4) 1.534(4) 1.00(3) 0.99(3) 0.97(3) 0.94(3) 1.00(3) 0.95(3) 1.04(3) 0.98(3) 0.93(3) 1.524(4) 1.529(4) 0.97(3) 0.96(3) 0.96(3) 0.91(3) 0.97(3) 0.95(3) 0.91(3) 1.517(4) 1.527(4) 0.93(3) 1.00(3) 0.88(3) 0.97(3) 0.98(3) 1.00(3) 0.95(3) 0.63(1) 0.9800 0.9800 0.99(4) 0.99(4) 0.89(4) 0.94(3) 0.93(3) 156 C27-H27C C28-H28A C28-H28B C28-H28C C29-H29A C29-H29B C29-H29C C30-H30A C30-H30B C30-H30C C31-H31A C31-H31B C31-H31C CpA-Y-CpB CpA-Y-C25A CpA-Y-C25B CpB-Y-C25A CpB-Y-C25B CpA-Y-Cen CpB-Y-Cen Cen-Y-C25A Cen-Y-C25B PlnA-PlnB C25B-Y-C29 C25A-Y-C29 C11-Si1-C12 C11-Si1-C1 C12-Si1-C1 C11-Si1-C6 C12-Si1-C6 C1-Si1-C6 C13-Si2-C14 C13-Si2-C2 C14-Si2-C2 C13-Si2-C7 C14-Si2-C7 C2-Si2-C7 C25A-Si3-C27 C25A-Si3-C26 C27-Si3-C26 C25A-Si3-C28 C27-Si3-C28 C26-Si3-C28 C27-Si3-C25B C26-Si3-C25B C28-Si3-C25B C25A-Si4-C31 C25A-Si4-C30 0.90(3) 0.88(3) 0.99(3) 0.96(3) 0.90(3) 0.94(3) 1.00(3) 0.94(3) 0.94(3) 0.91(3) 0.92(3) 0.87(3) 0.98(3) 116.1 127.5 113.2 109.1 123.6 121.5 115.3 52.3 52.4 80.7(1) 71.6(3) 72.15(12) 107.32(15) 109.24(14) 113.44(14) 115.14(14) 115.72(14) 95.65(12) 107.51(16) 119.13(14) 106.47(14) 112.79(14) 115.34(14) 95.48(12) 118.7(3) 111.3(2) 105.47(19) 107.9(2) 106.47(18) 106.4(2) 99.8(6) 116.2(4) 120.8(5) 118.6(3) 110.4(3) C31-Si4-C30 C31-Si4-C25B C30-Si4-C25B C25A-Si4-C29 C31-Si4-C29 C30-Si4-C29 C25B-Si4-C29 C5-C1-C2 C5-C1-Si1 C2-C1-Si1 C3-C2-C1 C3-C2-Si2 C1-C2-Si2 C4-C3-C2 C4-C3-H3 C2-C3-H3 C5-C4-C3 C5-C4-C15 C3-C4-C15 C4-C5-C1 C4-C5-H5 C1-C5-H5 C10-C6-C7 C10-C6-Si1 C7-C6-Si1 C8-C7-C6 C8-C7-Si2 C6-C7-Si2 C9-C8-C7 C9-C8-C19 C7-C8-C19 C10-C9-C8 C10-C9-H9 C8-C9-H9 C9-C10-C6 C9-C10-C22 C6-C10-C22 Si1-C11-H11A Si1-C11-H11B H11A-C11-H11B Si1-C11-H11C H11A-C11-H11C H11B-C11-H11C Si1-C12-H12A Si1-C12-H12B H12A-C12-H12B Si1-C12-H12C H12A-C12-H12C H12B-C12-H12C 108.0(2) 103.5(5) 129.3(6) 109.62(17) 105.70(16) 103.42(16) 104.9(4) 106.7(2) 129.8(2) 119.7(2) 106.3(2) 124.7(2) 124.2(2) 110.8(2) 122.1(17) 127.1(17) 105.8(2) 127.9(3) 125.2(2) 110.3(2) 124.3(17) 125.2(17) 106.7(2) 127.4(2) 122.5(2) 107.9(2) 129.0(2) 120.3(2) 107.6(2) 125.4(3) 126.4(2) 109.8(3) 125.6(17) 124.5(17) 107.9(2) 125.7(2) 126.0(2) 113.6(18) 114.8(17) 107(2) 110.1(17) 106(2) 105(2) 108.7(17) 112.1(18) 103(2) 113.7(18) 113(2) 106(2) 157 Si2-C13-H13A Si2-C13-H13B H13A -C 13-H13B Si2-C13-H 13C H 13A-C 13-H13C H13B-C13-H13C Si2-C14-H 14A Si2-C14-H14B H14A-C14-H14B Si2-C14-H14C H14A-C14-H14C H14B-C14-H14C C 16-C15-C4 C16-C15-C18 C4-C15-C18 C 16-C15-C17 C4-C15-C17 C 18-C15-C17 C15-C16-H16A C15-C16-H16B H16A-C16-H16B C15-C16-H16C H16A-C16-H16C H16B-C16-H16C C15-C17-H17A C15-C17-H17B H17A-C17-H17B C15-C17-H17C H17A-C17-H17C H17B-C17-H17C C15-C18-H18A C15-C18-H18B H18A-C18-H18B C15-C18-H18C H18A-C18-H18C H18B-C18-H18C C8-C19-C21 C8-C19-C20 C21-C19-C20 C8-C19-H19A C21-C19-H19A C20-C19-H19A C19-C20-H20A C19-C20-H20B H20 A -C20-H20B C19-C20-H20C H20A-C20-H20C H20B-C20-H20C C19-C21-H21A 109.2(17) 112.7(18) 104(2) 113(2) 103(3) 115(3) 108.5(17) 113.6(18) 107(2) 114.2(19) 102(2) 110(3) 111.3(2) 109.4(3) 111.4(2) 109.0(3) 108.0(2) 107.7(3) 111.4(18) 114.3(17) 105(2) 111.0(18) 109(3) 106(3) 111.9(18) 111.5(16) 108(2) 110.3(17) 110(2) 105(2) 111.5(17) 108.4(17) 109(2) 111.3(19) 111(2) 106(2) 113.7(3) 109.1(3) 110.2(3) 109.4(16) 105.9(17) 108.4(16) 112.9(17) 113.0(18) 105(2) 108.5(19) 112(3) 105(3) 109.6(18) C19-C21-H21B H21A-C21-H21B C19-C21-H21C H21A-C21-H21C H21B-C21-H21C C10-C22-C24 C10-C22-C23 C24-C22-C23 C10-C22-H22 C24-C22-H22 C23-C22-H22 C22-C23-H23A C 22-C23-H23B H23A-C23-H23B C22-C23-H23C H23A-C23-H23C H23B-C23-H23C C22-C24-H24A C22-C24-H24B H24A-C24-H24B C22-C24-H24C H24A-C24-H24C H24B-C24-H24C Si4-C25A-Si3 Si4-C25A-Y Si3-C25A-Y Si4-C25A-H25A Si3-C25A-H25A Y-C25A-H25A Si4-C25B-Si3 Si4-C25B-Y Si3-C25B-Y Si4-C25B-H25B Si3-C25B-H25B Y-C25B-H25B Si3-C26-H 26A Si3-C26-H26B H 26A-C26-H26B Si3-C26-H 26C H 26A-C26-H26C H26B-C26-H26C Si3-C27-H27A Si3-C27-H27B H27A-C27-H27B Si3-C27-H27C H27A-C27-H27C H27B-C27-H27C Si3-C28-H28A Si3-C28-H 28B 108.8(19) 109(2) 108.6(19) 110(3) 111(3) 113.1(3) 110.0(2) 110.0(3) 109.7(17) 105.9(17) 108.0(17) 109.7(16) 112.1(19) 110(2) 109.9(17) 109(2) 105(2) 111.1(16) 112.6(16) 105(2) 110.5(18) 110(2) 107(2) 118.5(2) 94.83(18) 139.3(3) 98.6 98.6 98.6 114.4(6) 95.4(4) 141.8(6) 99.1 99.1 99.1 103(2) 110(2) 100(3) 118(3) 116(3) 108(3) 107.8(19) 112.2(19) 110(3) 112(2) 109(3) 107(3) 106(2) 111.4(19) 158 H28A-C28-H28B Si3-C28-H28C H28A-C28-H28C H28B-C28-H28C Si4-C29-Y Si4-C29-H29A Y-C29-H29A Si4-C29-H29B Y-C29-H29B H29A-C29-H29B Si4-C29-H29C H29 A -C29-H29C H29B-C29-H29C Si4-C30-H30A Si4-C30-H30B H30A-C30-H30B Si4-C30-H 30C H30A-C30-H30C H30B-C30-H30C Si4-C31-H31A Si4-C31-H31B H31A-C31-H31B Si4-C31-H31C H31A-C31-H31C H31B-C31-H31C 107(3) 111(2) 112(3) 109(3) 83.34(11) 114.6(18) 72.8(18) 103.7(18) 172.3(18) 106(2) 115.6(16) 111(2) 104(2) 109(2) 110(2) 109(3) 113(2) 118(3) 97(3) 112(2) 108(2) 113(3) 112.8(19) 103(3) 109(3) CpA is the centroid of atoms C1, C2, C3, C4 and C5 PlnA is the best plane through atoms C1, C2, C3, C4 and C5 c CpB is the centroid of atoms C6, C7, C8, C9 and C10 d PlnB is the best plane through atoms C6, C7, C8, C9 and C10 a Cen is the centroid of atoms Si4 and C29 a b Table 12. Crystal Data and Structure Analysis Details for dlz6[(Me2 Si) 2 (11 5-4-CMe3 -C5 H 2 )(11 5 -3,5-CMe2 H-C 5H 1 )]Ta(CH2 )CH3 • Empirical formula Formula weight Crystallization solvent Crystal shape Crystal color Crystal size H 43Si2 Ta 592.73 diethyl ether I pentane twinned plate golden orange 0.07 x 0.18 x 0.19 mm C 26 Data Collection Type of diffractometer Wavelength Data collection temperature Theta range for 25 reflections used in lattice d etermination Unit cell dimensions Volume z Crystal system Space group CAD-4 0.71073 A MoKa 84K 13 to 18° a = 8.508(3) A b = 16.123(6) A c = 9.984(3) A 1266.3(8) A3 2 monoclinic a= 90° ~= 112.39(3) 0 y= 90° 159 Density (calculated) F(OOO) 1.555 g/cm3 Theta range for data collection Completeness to theta= 25° Index ranges Data collection scan type 600 2.21 to 25° 71.5% -10 ~ h ~ 10,-19 ~ k ~ 19,-11 ~ 1 ~ 11 co-scan Reflections collected Independent reflections 11978 1651 [Rint= 0.050; GOFmerge= 1.58] Reflections > 2cr(I) 1576 Average cr(l) I (net I) 0.0256 4.445 mm-1 Absorption coefficient Absorption correction Max. and min. transmission \If-scan 1.16 and 0.84 Number of standards Decay of standards 3 reflections measured every 75 min 0.5% Structure Solution and Refinement Primary solution method direct methods Secondary solution method difference map Hydrogen placement calculated Refinement method full-matrix least-squares on p2 Data I restraints I parameters 1651 I o I 140 Treatment of hydrogen atoms not refined, uiso fixed at 120% u .,q of attached atom Goodness-of-fit on p2 2.385 Final R indices [1>2cr(I), 1576 reflections] R1 = 0.0274, wR2 = 0.0659 R indices (all data) R1 = 0.0297, wR2 = 0.0664 sigma Type of weighting scheme used Weighting scheme used w= 1 I cr2 (Fo2 ) 0.017 Max shift/ error 0.001 Average shift/ error 1.577 and -0.823 e-A-3 Largest cliff. peak and hole Programs Used CAD-4 Software (Enraf-Nonius, 1989) Cell refinement CAD-4 Software (Enraf-Nonius, 1989) Data collection CRYM (Duchamp, 1964) Data reduction Bruker SHELXTL v5.1 Structure solution 160 Structure refinement Bruker SHELXTL v5.1 Special Refinement Details The crystals grow as twinned, golden orange plates. Samples were mounted on a glass fibers with Paratone-N oil. Finally a crystal was found for which a unit cell could be determined. Although this crystal was also twinned, orientation matrixes were obtained for both twin components. The reflection indices (h k 1) and (h' k' 1') for the two twin components are related as: 0 (h' k' !') -1 0 The twin may be described as a reflection twin across the [1 0 0] plane; the corresponding reciprocal space description is a rotation twin about the (1 0 axis as this axis is normal to the [1 0 0] plane. Since by the monoclinic symmetry, (h k 1) is equivalent to (h k 1), Two interpretations of the reciprocal lattice overlap are shown as additional figures. Data were collected with 1.0° (I)scans. Data which agreed poorly in a preliminary merging were recollected. The individual backgrounds were replaced by a background function of 28 derived from those reflections with I< 3cr(l). The first attempts at refinement included all measured reflections; those reflections which presumably included overlap between the two twin components were given two sets of indices corresponding to the two twins. A twin parameter relating the relative contributions of the two components was included in the least squares matrix. Various criteria were used to identified overlapping reflections. However none of these approaches were particularly successful, presumably since most reflections do not perfectly coincide. The measured intensities of these reflections would then not reflect the true sum of the two contributing components. Finally, all reflections with l = 3, 6, 9 and 11 were removed from the dataset; these reflections transform with h' deviating from integral values by 0.05, 0.10, 0.15 and 0.15, respectively. Therefore only the (h. k 0) reflections, which overlap perfectly with the (h -k 0) reflections of the twin, contain any twin contribution. The (h. -k 0) reflections were added as the symmetry equivalent (h. k 0) form. The GOF merge was 1.58 (1651 multiples) in point group 2 / m; due to the high redundancy of the data, there were no duplicates from which to calculate Rmerge· \f'-scan data were used for the absorption correction. There was 0.5% linear decay. No outlier reflections were omitted from the refinement. or Weights ware calculated as 1/ cr2 (F0 2 ); variances (cr2 (F0 2 )) were derived from counting statistics plus an additional term, (0.0141) 2; variances of the merged data were obtained by propagation of error plus another additional term, (0.014<1> )2 • The refinement of F2 is as always against all reflections. The weighted R-factor wR and goodness of fitS are based on F2 , conventional R-factors Rare based on F, with F set to zero for negative F 2 . The threshold expression of F2 > 2cr(F2 ) is 161 used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. The molecule lies on a mirror plane containing the Ta and bisecting both Cp rings; there is 1/2 molecule in the asymmetric unit. The t-butyl group is disordered about the mirror plane, as is seen in similar compounds. Splitting the three methyl carbon atoms into two sites each did not improve the model, so these atoms were left at single sites with elongated displacement ellipsoids. Unfortunately, the mirror plane also confuses the =CH2 and -CH 3 groups bound to the Ta. The principal axis of the displacement ellipsoid is perpendicular to the Ta to C bond. The h ydrogen atoms on this C15 were modeled with three calculated sites, as a normal CH3 group with one hydrogen atom pointing up with population one and the other two hydrogen atoms with population_. All hydrogen atoms were placed at calculated positions with U ;50 's fixed at 120% of the u eq of the attached atom. The minor twin component refined to a fractional population of 0.168(4). There are only two peaks greater than Ill e-A-3 in the final difference map: 1.57 e-A-3 (1.75A from H6) and 1.07 e-A-3 (0.79A from H6). Table 13. Bond lengths [A] and angles [0 ] for dlz6[(Me2 Si) 2 (TJ 5 -4-CMe 3 -C 5H 2 )(TJ 5-3,5-CMe2 H-C 5H 1 )]Ta(CH2 )CH3 • Ta-CpA a Ta-CpB c Ta···PlnA b Ta·· ·PlnB ct Ta-C15 Ta-C4 Ta-Cl Ta-C2 Ta-C5 Ta-C6 Ta-C3 Si-CS Si-C7 Si-Cl Si-C4 C1-C2 Cl-Cl(il C2-C3 C2-H2 C3-C9 C4-C5 C4-C4(i) C5-C6 C5-C12 C6-H6 2.129 2.139 2.117(4) 2.126(4) 2.155(7) 2.360(6) 2.369(5) 2.464(5) 2.514(5) 2.549(7) 2.579(7) 1.856(6) 1.857(7) 1.874(6) 1.891(5) 1.418(8) 1.449(10) 1.422(7) 0.9500 1.513(12) 1.434(8) 1.448(10) 1.416(7) 1.523(7) 0.9500 C7-H7A C7-H7B C7-H7C C8-H8A C8-H8B C8-H8C C9-C10 C9-Cll ClO-HlOA ClO-HlOB C10-H10C Cll-HllA Cll-HllB C12-C13 C12-C14 C12-H12 C13-H13A C13-H13B C13-H13C C14-Hl4A C14-H14B C14-H14C C15-H15A C15-H15B C15-H15C 0.9800 0.9800 0.9800 0.9800 0.9800 0.9800 1.440(10) 1.479(17) 0.9800 0.9800 0.9800 0.9600 0.9601 1.513(8) 1.524(8) 1.0000 0.9800 0.9800 0.9800 0.9800 0.9800 0.9800 0.9800 0.9800 0.9800 162 CpA-Ta-CpB CpA-Ta-C15 CpB-Ta-C15 PlnA-PlnB C15-Ta-C15<i> C8-Si-C7 C8-Si-C1 C7-Si-C1 C8-Si-C4 C7-Si-C4 C1-Si-C4 C2-C1-C1 <i> C2-C1-Si C1(i>_c1-Si C1-C2-C3 C1-C2-H2 C3-C2-H2 C2<il_C3-C2 C2-C3-C9 C5-C4-C4<i> C5-C4-Si C4(i>_C4-Si C6-C5-C4 C6-C5-C12 C4-C5-C12 C5-C6-C5<i> C5-C6-H6 Si-C7-H7A Si-C7-H7B H 7A-C7-H7B Si-C7-H7C H7A-C7-H7C H7B-C7-H7C Si-C8-H8A Si-C8-H8B H8A-C8-H8B Si-C8-H8C H8A-C8-H8C 125.4 107.1 107.4 67.0(3) 99.3(4) 106.9(3) 108.1(3) 116.5(3) 116.4(3) 116.7(3) 91.9(2) 106.8(3) 124.8(4) 122.55(17) 110.1(5) 124.9 124.9 106.0(7) 126.5(4) 107.5(3) 125.4(4) 122.23(16) 107.7(5) 125.2(5) 126.7(5) 109.4(7) 125.3 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 H8B-C8-H8C C10-C9-C10<il C10-C9-C11 C10-C9-C3 Cll-C9-C3 C9-C10-H10A C9-C10-H10B H10A-C10-H10B C9-C10-H10C H10A-C10-H10C H10B-C10-H10C C9-C11-H11A C9-C11-H11B H11A-C11-H11B C13-C12-C5 C13-C12-C14 C5-C12-C14 C13-C12-H12 C5-C12-H12 C14-C12-H12 C12-C13-H13A C12-C13-H13B H13A-C13-H13B C12-C13-H13C H13A-C13-H13C H13B-C 13-H13C C12-C14-H14A C12-C14-H14B H14A-C14-H14B C12-C14-H14C H14A-C14-H14C H14B-C14-H14C Ta-C15-H15A Ta-C15-H15B H15A-C15-H15B Ta-C15-H15C H15A-C15-H15C H15B-C15-H15C Symmetry transformations used to generate equivalent atoms: (i) x,-y+ 1 /2,z CpA is the centroid of atoms C1, C2, C3, C4 and C5 PlnA is the best plane through atoms C1, C2, C3, C4 and C5 c CpB is the centroid of atoms C6, C7, C8, C9 and C10 ct PlnB is the best plane through atoms C6, C7, C8, C9 and C10 a b 109.5 107.3(15) 106.5(9) 110.9(6) 114.3(8) 109.5 109.5 109.5 109.5 109.5 109.5 109.6 109.4 109.5 110.3(5) 109.1(4) 112.3(5) 108.4 108.4 108.4 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 163 Table 14. Crystal Data and Structure Analysis Details for dlz7Me 2 Si (C 5H 4 ) 2TaMe3 • Empirical formula Formula weight C 15H 23SiTa 412.37 Crystallization solvent Crystal shape Crystal color diethyl ether irregular chunk colorless 0.09 x 0.15 x 0.41 mm Crystal size Data Collection Type of diffractometer Wavelength CAD-4 0.71073 A MoKa Data collection temperature Theta range for 25 reflections used in lattice determination Unit cell dimensions 84K Volume z Crystal system Space group Density (calculated) F(OOO) Theta range for data collection Completeness to theta = 30° Index ranges Data collection scan type Reflections collected Independent reflections Reflections > 2cr(I) Average cr(I) I (net I) Absorption coefficient Absorption correction Max. and min. transmission Number of standards 16 to 19° a = 7.722(3) A b = 15.010(4) A c = 12.620(4) A 1462.7(8) A3 a= 90° 0 ~= 90.54(3) 'Y = 90° 4 monoclinic P 21 /n (# 14) 1.873 g/cm3 800 1.5 to 30° 100.0 % -10:::; h:::; 0,-21 :::; k:::; 21,-17:::; 1:::; 17 ro-scan 11938 4257 [Rint= 0.0234; GOFmerge= 1.73 ] 3974 0.0270 7.574 mm-1 'If-Scan 1.12 and 0.88 3 reflections measured every 75 min 164 Decay of standards no correction applied Structure Solution and Refinement Primary solution method Secondary solution method Hydrogen placement Refinement method Data I restraints I parameters direct methods difference map calculated full-matrix least-squares on p2 4257 I o I 224 Treatment of hydrogen atoms coordinates refined, Uiso fixed at 120% u eq of attached atom Goodness-of-fit on p2 2.555 Final R indices [l>2cr(l), 3974 reflections] R1 = 0.0350, wR2 = 0.0819 R indices (all data) Type of weighting scheme used Weighting scheme used Max shift I error Average shift I error Extinction coefficient Largest cliff. peak and hole R1 = 0.0377, wR2 = 0.0823 sigma 2 w= 1 I cr (Fo 2 ) 0.051 0.001 0.00133(16) 3.186 and -3.035 e·A-3 Programs Used Cell refinement Data collection Data reduction Structure solution Structure refinement CAD-4 Software (Enraf-Nonius, 1989) CAD-4 Software (Enraf-Nonius, 1989) CRYM (Duchamp, 1964) Bruker SHELXTL v5.1 Bruker SHELXTL v5.1 Special Refinement Details An irregular chunk was cut from a colorless blob and mounted on a glass fiber with Paratone-N oil. Data were collected with 1.1 o co-scans. Data which agreed poorly in a preliminary merging were recollected. The crystal turned brown during irradiation. The individual backgrounds were replaced by a background function of 29 derived from those reflections with I< 8cr(I). The GOFmerge was 1.73 (3408 multiples) in point group 2Im; Rmerge was 0.0207 for 3088 duplicates with F 0 > 0. '¥-scan data were used for the absorption correction. The three check reflections behaved erratically (or anisotrpically), showing changes of -2.6, -1.5 and 3.3% during data collection; accordingly, no correction was applied. Some reflections were lost due to a power failure (11589 -12116). The last reflections collected merged poorly and so the range 8900-12466 was deleted from the data 165 file, leaving 8899 reflections. As these were redundant data or recollections of poorly merging multiples, there are no gaps in the data. Weights ware calculated as 1/cr2 (F0 2 ); variances (~(F 02 )) were derived from counting statistics plus an additional term, (0.0141) 2; variances of the merged data were obtained by propagation of error plus another additional term, (0.014<1> )2 • The refinement of F 2 is as always against all reflections. The weighted R-factor wR and goodness of fitS are based on F2 , conventional R-factors Rare based on F, with F set to zero for negative F 2 . The threshold expression of F2 > 2cr(F2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. There is one molecule in the asymmetric unit. Although the~ angle of 90.54(3) 0 is -90° and the molecule possesses internal symmetry, the structure is clearly monoclinic. The 0 11 reflection was an outlier and omitted from the refinement. A SHELXL extinction coefficient refined to 0.00133(16). There are a number of large peaks in the final difference map; the three greater than 11.51 e-A-3 are all near theTa atom: 3.19 e-A-3 at 0.70 A from Ta, -3.04 e-A-3 at 0.65 A from Ta and 2.93 e -A-3 at 0.71 A from Ta. Table 15. Bond lengths [A] and angles [0 ] for dlz7Me 2 Si (C5 H 4 ) 2TaMe3 • Ta-CpA ~ Ta-CpB c Ta· ··PlnA b Ta···PlnB ct Ta-C14 Ta-C13 Ta-C15 Si-C11 Si-C12 Si-C1 Si-C6 C1-C5 C1-C2 C2-C3 C2-H2 C3-C4 C3-H3 C4-C5 C4-H4 C5-H5 C6-C7 C6-C10 C7-C8 C7-H7 2.125 2.125 2.124 2.125 2.277(6) 2.300(6) 2.310(6) 1.846(6) 1.856(6) 1.869(5) 1.874(5) 1.426(7) 1.432(7) 1.425(7) 0.82(7) 1.403(8) 0.90(7) 1.419(7) 0.93(7) 0.95(6) 1.420(7) 1.436(7) 1.420(7) 0.77(6) C8-C9 C8-H8 C9-C10 C9-H9 C10-H10 Cll-HllA Cll-HllB Cll-HllC C12-H12A C12-H12B C12-H12C C13-H13A C13-H13B C13-H13C C14-H14A C14-H14B C14-H14C C15-H15A C15-H15B C15-H15C CpA-Ta-CpB CpA-Ta-C13 CpA-Ta-C14 CpA-Ta-C15 1.398(8) 0.89(7) 1.407(7) 0.98(7) 0.90(7) 0.95(7) 0.92(7) 0.88(7) 0.97(7) 0.81(7) 1.00(6) 0.87(8) 0.95(7) 0.87(7) 0.86(8) 0.95(8) 0.94(8) 1.03(7) 1.00(8) 0.91(8) 128.3 99.0 115.8 98.2 166 CpB-Ta-C13 CpB-Ta-C14 CpB-Ta-C15 PlnA-PlnB C14-Ta-C13 C14-Ta-C15 C13-Ta-C15 C11-Si-C12 C11-Si-C1 C12-Si-C1 C11-Si-C6 C12-Si-C6 C1-Si-C6 C5-C1-C2 C5-C1-Si C2-C1-Si C3-C2-C1 C3-C2-H2 C1-C2-H2 C4-C3-C2 C4-C3-H3 C2-C3-H3 C3-C4-C5 C3-C4-H4 C5-C4-H4 C4-C5-C1 C4-C5-H5 C1-C5-H5 C7-C6-C10 C7-C6-Si C10-C6-Si C6-C7-C8 C6-C7-H7 C8-C7-H7 C9-C8-C7 C9-C8-H8 C7-C8-H8 98.2 115.9 98.6 55.0(2) 69.8(3) 70.6(3) 140.3(2) 115.7(3) 111.8(2) 111.9(2) 111.9(3) 110.0(2) 93.4(2) 105.7(4) 124.5(4) 124.2(4) 109.1(4) 124(5) 127(5) 107.8(5) 125(4) 127(4) 108.0(5) 129(4) 123(4) 109.4(4) 124(4) 127(4) 105.6(4) 124.4(4) 124.1(4) 109.3(5) 125(5) 125(5) 107.6(5) 130(4) 123(4) C8-C9-C10 C8-C9-H9 C10-C9-H9 C9-C10-C6 C9-C10-H10 C6-C10-H10 Si-C11-H11A Si-C11-H11B H11A-C11-H11B Si-C11-H11C H11A-C11-H11C H11B-C11-H11C Si-C12-H12A Si-C12-H12B H12A-C12-H12B Si-C12-H12C H12A-C12-H12C H12B-C12-H12C Ta-C13-H13A Ta-C13-H13B H13A-C13-H13B Ta-C13-H13C H13A-C13-H13C H13B-C13-H13C Ta-C14-H14A Ta-C14-H14B H14A-C14-H14B Ta-C14-H14C H14A-C14-H14C H14B-C14-H14C Ta-C15-H15A Ta-C15-H15B H15A-C15-H15B Ta-C15-H15C H15A-C15-H15C H15B-C15-H15C " CpA is the centroid of atoms C1, C2, C3, C4 and C5 b PlnA is the best plane through atoms C1, C2, C3, C4 and C5 c CpB is the centroid of atoms C6, C7, C8, C9 and C10 ct PlnB is the best plane through atoms C6, C7, C8, C9 and C10 108.5(5) 122(4) 129(4) 108.9(5) 129(4) 122(4) 112(4) 109(4) 103(6) 106(4) 112(6) 115(6) 109(4) 113(5) 115(6) 108(4) 108(5) 104(6) 119(5) 114(4) 102(6) 115(5) 100(7) 104(6) 109(5) 112(5) 98(6) 124(5) 113(7) 99(6) 111(4) 101(4) 96(5) 106(5) 104(6) 138(6) 167 Table 16. Crystal Data and Structure Analysis Details for dlz8[(Me 2 Si) 2 ('Jl 5-4-CMe 3 -C 5H 2 )('Jl 2-3,5-CMe 2 H-C 5H 1 )]TaMe3 • Empirical formula Formula weight Crystallization solvent Cz7H 46Si2Ta 607.77 diethyl ether I petroleum ether tapered block Crystal shape tangerine Crystal color 0.19 x 0.28 x 0.33 mm Crystal size Data Collection Preliminary photograph(s) rotation Type of diffractometer Bruker SMART 1000 ccd Wavelength 0.71073 A MoKa Data collection temperature 98K Theta range for 7898 reflections used in lattice determination 2.4 to 28.5° Unit cell dimensions a = 16.9762(8) A a= 90° P= goo b = 16.2378(8) A c = 9.8844(5) A 'Y =goo 2724.7(2) A3 Volume z 4 Crystal system Space group Density (calculated) F(OOO) Theta range for data collection Completeness to theta= 28.54° Index ranges Data collection scan type orthorhombic Pnma (# 62) 1.482 glcm3 1236 2.38 to 28.54o 96.6% -22 ~ h ~ 22, -21 ~ k ~ 21, -13 ~ 1 ~ 12 ffi scans at 6 fixed <p values 4647g 3468 [Rint= 0.06g8] Reflections collected Independent reflections Reflections > 2cr(I) Average cr(I) I (net I) Absorption coefficient Absorption correction Number of standards Decay of standards 321g 0.0216 4.134 mm-1 none first scans recollected at end of runs within counting statistics 168 Structure Solution and Refinement Primary solution method Secondary solution method Hydrogen placement Refinement method Data I restraints I parameters direct m ethods difference map calculated full-matrix least-squares on F2 3468 I o I 157 Treatment of hydrogen atoms not refined, uiso fixed at 120% u eg of attached atom Goodness-of-fit on F2 2.547 Final R indices [1>2cr(I), 3219 reflections] R1 = 0.0450, wR2 = 0.1515 R indices (all data) Type of weighting scheme used Weighting scheme used Max shift/ error Average shift/ error Largest diff. peak and hole R1 = 0.0479, wR2 = 0.1545 sigma w=1/[cr2 (F0 2 ) + (0.05P) 2 ] 0.020 0.001 10.876 and -4.558 e·A-3 Programs Used Cell refinement Data collection Data reduction Structure solution Structure refinement Bruker SAINT v6.02 Bruker SMART v5.606 Bruker SAINT v6.02 Bruker SHELXTL v5.1 Bruker SHELXTL v5.1 Special Refinement Details A tapered block was cut from a large irregular lumpish tangerine-colored crystal and was mounted on a glass fiber with Paratone-N oil. Six runs of data were collected with 18 second long, -0.25° wide w-scans at six values of <p (0, 120, 240, 60, 180, 90 and 300°) with the detector 5 em (nominal) distant at a e of -28°. The initial cell for data reduction was calculated from just under 1000 reflections chosen from throughout the data frames. For data processing with SAINT v6.02, all defaults were used, except: a fixed box size of 1.8 x 1.8 x 0.6 was used, profiles for the nine detector areas were blended, periodic orientation matrix updating was disabled, the instrument error was set to zero, n o Laue class integration restraints were u sed, and for the post-integration global least squares refinement, no constraints were applied. No decay correction was n eede d . A data set corrected with SADABS v. 2.0 (beta) showed no improvement and consequently was not used. The data were intense and a weighting scheme of w =1 / [if(F0 2 ) + (0.05P)2 ] was u sed, where P = [2F/ + max(F0 2 ,0)] I 3. 169 There is 1/2 molecule in the asymmetric unit; the molecule lies on the mirror plane (Wyckoff site c). The mirror plane bisects both cyclopentadienyl rings and contains five atoms: Ta, C3 and C6 (cyclopentadienyl carbons), C15 (central tantalum methyl carbon), and C16 (t-butyl carbon). The three methyl carbons on the t-butyl group are disordered about the mirror plane; consequently the population ratio is 50:50. This disorder is common in similar t-butyl substituted metallocenes. In particular this compound is essentially isostructural with the trimethysilyl-substituted analog, TMSThpTaMe3 (PJC 22). These structures differ in the orientation of the 4substituent on the cyclopentadienyl ring; in the latter case, one of the silyl-methyl bonds is oriented towards the center of the metallocene wedge. The orientation of this substituent is rotated 180° with respect to the t-butyl substituent of this structure. No reflections were specifically omitted from the final processed dataset; 2369 reflections were rejected, with 50 space group-absence violations, 218 inconsistent equivalents and no reflections suppressed. Refinement of F 2 was against all reflections. The weighted R-factor (wR) and goodness of fit (S) are based on F2 , conventional R-factors (R) are based on F, with F set to zero for negative F 2 • The threshold expression of F 2 > 2cr( F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. This dataset is typical for a tantalum containing compound on the CCD. There are many large peaks in the final difference map; the eight greater than Ill e-A-3 are: 10.88, -4.56, -1.67, 1.61, -1.60 and 1.19 e -A-3 at 0.55 to 1.37A from Ta, 1.01 e-A3 at 0.47A from ClO and 1.01 e-A-3 at 0.84A from C4. Table 17. Bond lengths [A] and angles [ for dlz8- [(Me2 Si) 2 (fl 5 -4CMe3-C5H2) (fl 2-3,5-CMe2 H -C 5 H 1 ) ]TaMe3 • 0 ] Ta-Cl Ta-C2 Ta-C3 Ta-C4 Ta-C14 Ta-C15 Ta···PlnAa Ta···PlnB b Ta-CpA c Ta···CpBct Ta-Cen e Si-Cl Si-C4 Si-C7 Si-C8 2.392(4) 2.484(4) 2.593(7) 2.465(4) 2.215(6) 2.222(7) 2.140(3) 2.129(7) 2.150 2.895 2.349 1.862(4) 1.863(4) 1.870(6) 1.871(6) Cl-C2 Cl-Cli C2-C3 C2-H2 C3-C16 C4-C5 C4-C4i C5-C6 CS-Cll C6-H6 C7-H7A C7-H7B C7-H7C C8-H8A C8-H8B C8-H8C 1.422(6) 1.458(9) 1.423(6) 0.9300 1.518(9) 1.423(6) 1.499(9) 1.408(5) 1.518(6) 0.9300 0.9600 0.9600 0.9600 0.9600 0.9600 0.9600 170 C9A-C16 C9A-H9A C9A-H9B C9A-H9C C10-C16 C10-H10A C10-H10B C10-H10C C9B-C16 C9B-H9D C9B-H9E C9B-H9F Cll-C13 Cll-C12 Cll-H11 C12-H12A C12-H12B C12-H12C C13-H13A C13-H13B C13-H13C C14-H14A C14-H14B C14-H14C C15-H15A C15-H15B C14-Ta-C14i C14-Ta-C15 PlnA-PlnB CpA-Ta···CpB CpA-Ta-Cen CpA-Ta-C14 CpA-Ta-C15 Cen-Ta-C14 Cen-Ta-C15 C1-Si-C4 C1-Si-C7 C4-Si-C7 C1-Si-C8 C4-Si-C8 C7-Si-C8 C2-C1-C1i C2-C1-Si C1i-C1-Si C1-C2-C3 C1-C2-H2 C3-C2-H2 C2i-C3-C2 1.663(12) 0.9600 0.9600 0.9600 1.493(14) 0.9600 0.9600 0.9600 1.447(13) 0.9600 0.9600 0.9600 1.532(6) 1.534(6) 0.9800 0.9600 0.9600 0.9600 0.9600 0.9600 0.9600 0.9600 0.9600 0.9600 0.9684 0.9563 113.4(4) 75.15(16) 112.75(24) 115.7 97.6 103.3 176.8 117.7 85.6 93.7(2) 115.4(3) 115.9(3) 108.1(2) 116.6(2) 106.8(4) 106.3(3) 125.1(3) 123.17(14) 111.4(4) 124.3 124.3 104.7(5) C2-C3-C16 C5-C4-C4i C5-C4-Si C4i-C4-Si C6-C5-C4 C6-C5-C11 C4-C5-C11 C5-C6-C5i C5-C6-H6 Si-C7-H7A Si-C7-H7B H7A-C7-H7B Si-C7-H7C H7A-C7-H7C H7B-C7-H7C Si-C8-H8A Si-C8-H8B H8A-C8-H8B Si-C8-H8C H8A-C8-H8C H8B-C8-H8C C16-C9A-H9A C16-C9A-H9B H9A-C9A-H9B C16-C9A-H9C H9A-C9A-H9C H9B-C9A-H9C C16-C10-H10A C16-C10-H10B H10A-C10-H10B C16-C10-H10C H10A-C10-H10C H10B-C1 0-H10C C16-C9B-H9D C16-C9B-H9E H9D-C9B-H9E C16-C9B-H9F H9D-C9B-H9F H9E-C9B-H9F C5-C11-C13 C5-C11-C12 C13-C11-C12 C5-C11-H11 C13-C11-H11 C12-C11-H11 C11-C12-H12A C11-C12-H12B H12A-C12-H12B C11-C12-H12C 127.4(3) 106.1(3) 129.1(3) 122.40(14) 109.5(4) 125.6(4) 124.9(4) 108.6(5) 125.7 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 111.0(4) 112.8(4) 109.0(4) 108.0 108.0 108.0 109.5 109.5 109.5 109.5 171 H12A-C12-H12C H12B-C12-H12C C11-C13-H13A C11-C13-H13B H13A -C13-H13B C11-C13-H13C H13A-C13-H13C H13B-C13-H13C Ta-C14-H14A Ta-C14-H14B H14A-C14-H14B Ta-C14-H14C 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 H14A-C14-H14C H14B-C14-H14C Ta-C15-H15A Ta-C15-H15B H15A-C15-H15B C9B-C16-C10i C9B-C16-C3 C10-C16-C3 C9B-C16-C9Ai C10-C16-C9A C3-C16-C9A Symmetry transformations used to generate equivalent atoms: (i) x,-y+ 1 / 2,z ~ PlnA is the best plane through atoms C1, C2, C3, C1i and C2i PlnB is the best plane through atoms C4, C5, C6, C4i and C5i CpA is the centroid of atoms C1, C2, C3, Cl' and C2i ct CpB is the centroid of atoms C4, C5, C6, C4' and C5' e Cen is the centroid of atoms C4 and C4' b c 109.5 109.5 109.2 109.7 109.1 111.3(10) 113.6(6) 108.5(7) 108.5(11) 105.2(9) 109.4(5)