Oxo, imido, and borollide complexes of tantalum and zirconium Citation Quan, Roger Weihong (1994) Oxo, imido, and borollide complexes of tantalum and zirconium. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/0351-pe35. https://resolver.caltech.edu/CaltechTHESIS:07052012-161238837 Abstract The preparation of reactive oxo, imido, and borollide complexes on tantalum and zirconium will be described. Metathesis of Cp* 2 Ta(=O)Cl with AgPF 6 afforded [Cp* 2 TaF 2 HPF 6 ], which presumably formed from P-F activation of PF6 - . When AgS0 3 CF 3 was used, [Cp* 2 Ta(=O)][S0 3 CF 3 ] was isolated; however, it was unreactive toward styrene, methane, or benzene. Exposure to water resulted in the 1,2-addition product, [Cp* 2 Ta(OH) 2 ][S0 3 CF 3 ]. Finally, treating Cp* 2 Ta(=O)H with [Ph 3 C][B(C 6 F 5 ) 4 ] afforded [Cp* 2 Ta(=O)][B(C 6 F 5 ) 4 ]. Even with this non-coordinating counterion, the complex was found to be surprisingly unreactive. To prepare an imido complex, treating Cp*TaCl 4 with four equivalents of lithium anilide affords Cp*Ta(=NPh)(NHPh) 2 . This complex reacts readily with substituted anilines to generate Cp*Ta(=NPh')(NHPh') 2 and with alcohols such as pinacol to afford Cp*Ta(OCMe 2 CMe 2 O) 2 , products whereby both the imido and amido groups are exchanged. Exposing Cp*Ta(=NPh)(NHPh) 2 to C0 2 resulted in the isolation of Cp*Ta(OCONPh)(η 4 -OCONHPh) 2 with both the formal [2+2] addition of C0 2 across the imido group and insertion of C0 2 into the amido group. Finally, bis-imido complexes were prepared by treating Cp*Ta(=NPh)(NHPh) 2 to one equivalent of HCl to yield Cp*Ta(=NPh) 2 or by treating Cp*TaCl 4 with four equivalents of lithium 2,6-diisopropylanilide to yield Cp*Ta(=NPh") 2 . The borollide ligand, (C 4 H 4 BN i Pr 2 ) 2- , ligand is introduced by treating Cp*ZrCl 3 with one equivalent of Li 2 (C 4 H 4 BN i Pr 2 )•THF to generate Cp*(C 4 H 4 BN i Pr 2 )ZrCl•LiCl. This complex contains a η 5- coordinated borollide ligand, as shown by an X-ray crystal structure analysis. Alkylation and arylation with trimethylsilylmethyllithium, benzylpotassium or phenyllithium yielded Cp*(C 4 H 4 BN i Pr 2 )ZrR complexes. These catalysts polymerizes ethylene, but only oligomerizes α-olefins. In addition, Cp*(C 4 H 4 BN i Pr 2 )ZrCl•LiCl has been found to exhibit the formal heterolytic cleavage of HCl and CH 3 I, affording Cp*(C 4 H 4 BNH i Pr 2 )ZrCl 2 and Cp*(C 4 H 4 BN i Pr 2 )ZrCl(I), respectively. Finally, treatment of Cp*(C 4 H 4 BN i Pr 2 )ZrCl•LiCl with LiNH t Bu generated the zwitterionic complex, Cp*(C 4 H 4 BNH i Pr 2 )Zr=N t Bu. Item Type: Thesis (Dissertation (Ph.D.)) Subject Keywords: 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: Unknown, Unknown Defense Date: 1 November 1993 Record Number: CaltechTHESIS:07052012-161238837 Persistent URL: https://resolver.caltech.edu/CaltechTHESIS:07052012-161238837 DOI: 10.7907/0351-pe35 Default Usage Policy: No commercial reproduction, distribution, display or performance rights in this work are provided. ID Code: 7169 Collection: CaltechTHESIS Deposited By: INVALID USER Deposited On: 05 Jul 2012 23:26 Last Modified: 16 Apr 2021 23:00 Thesis Files Preview PDF - Final Version See Usage Policy. 21MB Repository Staff Only: item control page

Oxo, Imido, and Borollide Complexes of Tantalum and Zirconium Thesis by Roger W . Quan 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 1994 (Submitted November 1. 1993) ii For Dad, Mom , William , Feng, and Tony 111 I shall pass through this world but once. Any good that I can do, or any kindness that I can show another human being, let me do it now and not defer it. For I shall not pass this way again . Author unknown lV First, I want to thank John Bercaw for giving me the opportunity to work in the group. John is a great advisor and leader for the group, providing the optimal situation for a graduate student to grow and learn from him, other graduate students and post-docs within the group. Other members of the Caltech faculty and staff who have helped during my stay include Bill Schaefer, Dick Marsh, and Larry Henling for solving the crystal structures which are shown in these chapters. Fenton Harvey assisted in all of the analyses. Joe Ziller at the Univerisity of California-Irvine solved the secorid structure in Chapter 3 and Terry Burkhardt at Exxon obtained the GPC data for the polyethylene samples in Chapter 4. Former and current Bercaw group members have been instrumental in my learning and experience here. LeRoy Whinnery was a guiding hand during my initial experiences with handling reactions on the vacuum line. Pam Shapiro was a source of inspiration through candidacy. In 213, Donnie Cotter worked on the line with me and put up with me listening to Pirate Radio until he could stand it no more and left to work with Sharad!!! (Just kidding.) Without Bryan Coughlin, it would have been quite different working here. During our five years here, it seems like I was always asking Bryan questions about life, love, and the pursuit of a Ph.D. My other classmate, Eric Kelson, helped with the electrochemistry described in Chapter one. Andy Kiely has been a great vaccurn line mate and coach of the Hogs this last year, allowing me playing time at third base and continuing the Bryan tradition of letting me bat lead-off. (Bo knows enough chemistry for another Ph.D, Andy!!!) Another 213 companion, Bob Blake provided the lab with easy listening tapes which included Van Halen, Scorpions and Metallica. Rock on!! Howie rules, Bob!! Sharad Hajela made coffee many mornings during the writing of this document while Mike Abrams (Coffee Czar) provided the beans. Tim Herzog kept me on my toes when he carne to bat during batting practice while Shannon Stahl was the recipient of a "few" high throws to first base. The group has also been fortunate to have some outstanding post-docs here. John Power seemed to always have a reference for you if y ou needed one. Gui Bazan started the project described in Chapter 4 by introducing the ligand to both scandium and zirconium. Helpful discussions with Jon Mitchell on imido chemistry provided insight into its chemistry. Finally, v Eugene Mueller shocked me by seemingly writing as much as I did when he read my thesis chapters. Outside of the group, Sunney Chan has been a second father for me. Laura Mizoue has been a great dinner companion and a great friend as well. A special thanks to Gary, Nancy and Benjamin Shreve for providing a place to go to for Thanksgiving dinner. Others in the Lewis group have provided a source of relaxation and fun, especially during my last year here. Paul Laibinis has been a great roommate. How can one not miss Colby Stanton's "Are you busy?", Ming Tan's promptness (NOT!) on dinner and movie excursions, or Janet Kesselman's threat to dump a glass of water on you (of course for a good reason!!). Financial support for this work was provided by the National Science Foundation. vi Abstract: The preparation of reactive oxo, imido, and borollide complexes on tantalum and zirconium will be described. Metathesis of Cp*2Ta(=O)Cl with AgPF6 afforded [Cp*2TaF2HPF6], which presumably formed from P-F activation of PF6-. When AgS03CF3 was used, [Cp*2Ta(=O)][S03CF3] was isolated; however, it was unreactive toward styrene, methane, or benzene. Exposure to water resulted in the 1,2-addition product, [Cp*2Ta(OH)2][S03CF3]. Finally, treating Cp*2Ta(=O)H with [Ph3C][B(C~s)4] afforded [Cp*2Ta(=O)][B(C~s)4]. Even with this non-coordinating counterion, the complex was found to be surprisingly unreactive. To prepare an imido complex, treating Cp*TaCl4 with four equivalents of lithium anilide affords Cp*Ta(=NPh)(NHPh)2. This complex reacts readily with substituted anilines to generate Cp*Ta(=NPh')(NHPh'h and with alcohols such as pinacol to afford Cp*Ta(OCMe2CMe20h, products whereby both the imido and amido groups are exchanged. Exposing Cp*Ta(=NPh)(NHPhh to C02 resulted in the isolation of Cp*Ta(OCONPh)(ll2-0CONHPhh with both the formal [2+2] addition of C02 across the imido group and insertion of C02 into the amido group. Finally, bis-irnido complexes were prepared by treating Cp*Ta(=NPh)(NHPhh to one equivalent of HCl to yield Cp*Ta(=NPhh or by treating Cp*TaCl4 with four equivalents of lithium 2,6-diisopropylanilide to yield Cp*Ta(=NPh"h. The borollide ligand, (C4H4BNiPr2)2-, ligand is introduced by treating Cp*ZrCl3 with one equivalent of Li2(C4H4BNiPr2)·THF to generate Cp*(C4H4BNiPr2)ZrCl·LiCl. This complex contains a ,s_ coordinated borollide ligand, as shown by an X-ray crystal structure analysis. Alkylation and arylation with trimethylsilylmethyllithium, benzylpotassium or phenyllithium yielded Cp*(C4H4BNiPr2)ZrR complexes. These catalysts polymerizes ethylene, but only oligomerizes a-olefins. In addition, Cp*(C4H4BNiPr2)ZrCl·LiCl has been found to exhibit the formal heterolytic cleavage of HCl and CH3I, affording Cp*(C4H4BNHiPr2)ZrCl2 and Cp*(C4H4BN(CH3)iPr2)ZrCl(I), respectively. Finally, treatment of Cp*(C4H4BNiPr2)ZrCl·LiCl with LiNHtBu generated the zwitterionic complex, Cp*(C4H4BNHiPr2)Zr=NtBu. Vll TABLE OF CONTENTS Acknowledgments iv Abstract vi Table of Contents vii List of Figures viii List of Tables ix Chapter 1: Homogeneous and Heterogeneous Oxo and Imido Complexes 1 Chapter 2: Reactive Cationic Tantalum Oxo Complexes 9 Chapter 3: [2+2] Cycloaddition, Insertion, and Substitution Reactions of Tantalum Imido and Amido Complexes 42 Chapter 4: Polymerization and Heterolytic Cleavage Reactions with Zirconium Borollide Complexes 92 viii LIST OF FIGURES Chapter 1 Figure 1. Representative examples of homogeneous oxidation reactions. 5 Figure 2. Representative examples of homogeneous metal imido mediated reactions. 6 Figure 1. Frontier molecular orbitals of bent metallocenes. 12 Figure 2. ORTEP diagram of [Cp*2TaF2JPF6 (20). 20 Figure 3. ORTEP diagram of [Cp*2Ta(OH)2)[S03CF3] (22). 22 Figure 4. ORTEP diagram of [Cp*2Ta(OH)(Cl))[S03CF3] (23). 23 Figure 1. Frontier molecular orbitals for a bent metallocene and [Cp*M(=NR)] fragment. 51 Figure 2. ORTEP diagram of Cp*Ta(=NPh)(NHPhh (32) with 50% probability ellipsoids. 56 Figure 3. ORTEP diagram of Cp*Ta(OCONPh)(TJ2-0CONHPhh 61 Chapter 2 Chapter 3 (36). Chapter 4 Figure 1. ORTEP diagram of Cp*(C4H4BNiPr2)ZrCl·LiCl(Et20h 104 (27). Figure 2. Hapticity of the zirconium borollide. 105 ix LIST OFTABLES Chapter 2 Table I 1H NMR Spectral Data for complexes 19- 25. 29 Table II 19F NMR Spectral Data for complexes 20- 24. 29 Table III 13C NMR Spectral Data for complexes 19- 25. 30 Table IV 31 P NMR Spectral Data for complex 20. 30 Table V. Crystal and Intensity Collection Data for [Cp*2TaF2][PF6] (20). 34 Table VI. Final Heavy Atom Parameters for [Cp*2TaF2HPF6] (20). 35 Table VII. Anisotropic Displacement Parameters for [Cp*2TaF2][PF6] (20). 37 Table VIII. Complete Distances and Angles for [Cp*2TaF2HPF6] (20). 38 Table IX. Assigned Hydrogen Atom Parameters for [Cp*2TaF2HPF6l (20). 41 Table I Fenske Hall Frontier Orbital Calculations for [Cp2Zr] fragment. 52 Table II Fenske Hall Frontier Orbital Calculations for CpNb(=NR) fragment. 52 Table III Selected Distances (A) and bond angles (deg) for Cp*Ta(=NPh)(NHPhh (32). 57 Table IV. lH NMR Spectral Data for complexes 30- 38. 68 Table V. 13C NMR Spectral Data for complexes 30 - 38. 69 Chapter 3 X Table VI. Crystal and Intensity Collection Data for Cp*Ta(=NPh)(NHPh)2 (32). 75 Table VII. Final Heavy Atom Parameters for Cp*Ta(=NPh)(NHPh)2 (32). 76 Table VIII. Anisotropic Displacement Parameters for Cp*Ta(=NPh)(NHPhh (32). 78 Table IX. Complete Distances and Angles for Cp*Ta(=NPh)(NHPh)2 (32). 79 Table X. Assigned Hydrogen Atom Parameters for Cp*Ta(=NPh)(NHPhh (32). 82 Table XI. Crystal and Intensity Collection Data for Cp*Ta(OCONPh)(Tt2-0CONHPh)2 (36). 83 Table XII. Final Heavy Atom Parameters for Cp*Ta(OCONPh)(Tt2-0CONHPh)2 (36). 84 Table XIII. Complete Distances for Cp*Ta(OCONPh)(Tt2-0CONHPh)2 (36). 86 Table XIV. Complete Angles for Cp*Ta(OCONPh)(Tt2-0CONHPh)2 (36). 88 Table XV. Assigned Hydrogen Atom Parameters for Cp*Ta(OCONPh)(Tt2-0CONHPh)2 (36). 90 lH NMR Spectral Data (Bo = (C4H4BNiPr2)) for complexes 28 - 38. 117 Chapter 4 Table I xi Table ll 13C NMR Spectral Data (Bo = (C4H4BNiPr2)) for complexes 28 - 38. 120 Table Ill. Crystal and Intensity Collection Data for Cp*(C4H4BNiPr2)ZrCl·LiCl(Et20h (27). 127 Table IV. Final Heavy Atom Parameters for Cp*(C4H4BNiPr2)ZrCl·LiCl(Et20h (27) . 128 Table V. Anisotropic Displacement Parameters for Cp*(C4H4BNiPr2)ZrCl·LiCl(Et20h (27). 130 Table VI. Complete Distances and Angles for Cp*(C4H4BNiPr2)ZrCl·LiCl(Et20h (27). 131 Table VII. Assigned Hydrogen Atom Parameters for Cp*(C4H4BNiPr2)ZrCl·LiCl(Et20h (27). 135 Chapter 1 Heterogeneous and Homogeneous Oxo and Imido Complexes ABSTRACT ................................................................................. 2 REFERENCES .............................................................................. 7 2 Abstract: A brief introduction to transition metal oxo and imido complexes is provided as background to Chapters 2 and 3. 3 Metal oxo and imido complexes have been prepared to model both important industrial processes and enzymatic reactions. Industrially, the oxidation of organic substrates is important in the conversion of feedstock hydrocarbons to profitable chemicals. For example, four million tons of aldehyde is produced annually from alkenes by the Wacker Process.l 0 II CH3C-H The mechanism of this catalytic process has been thoroughly investigated and, interestingly, oxygen is not directly involved in oxidizing ethylene.2 Rather, ethylene coordinates to PdCl2 and nucleophilic attack by water results in a palladium hydroxyethyl complex. The resulting palladium species is reoxidized by a process mediated by cuprous chloride with oxygen as the cooxidant) On the other hand, the oxidation of propene to acrolein by the heterogeneous metal-oxo catalyst, Bi203/Mo03, is not well understood . Bi 20 3/ Mo0 3 400°C 0 II CH2=CH-CH An oxo species is believed to be involved since stoichiometric conversion with Bi203/Mo03 is possible . The currently accepted mechanism is shown in Scheme I. The initial formation of an allyl species is followed by the formal addition reaction to the molybdenum-oxo bond, resulting in 3. The catalytic cycle is then completed by loss of acrolein and re-oxidation of the surface molybdenum by oxygen. 4 Scheme I ~\//0 0 II Bi, _.....Mo=O ~ 0 Bi, _.....Mo=O ~ 0 1 2 HO I y ~ ~H )~ HO I I y / y Bi, _.....Mo=O ~ 0 3 The related ammoxidation of propene to acrylonitrile can be accomplished using the bismuth molybdate catalyst that is used to synthesize acrolein. This methodology is used in the production of 8 billion pounds of acrylonitrile each year in the United States. Bi 20 3/ Mo0 3 400°C CH2=CH-C=N The proposed mechanism for the conversion is similar to that for the acrolein synthesis (Scheme I) except that ammonia reacts with surface oxo groups to form imido moieties. In fact, several models of the proposed intermediates have been prepared which are capable of simulating some of the steps in the catalytic cycle.4 Another important industrial process is the commercial conversion of butane and butene to maleic anhydride, which is utilized in the manufacture of resins, food additives and pharmaceuticals. Employing a vanadium phosphorous oxide catalyst, 1.3 billion pounds of maleic anhydride is produced annually.S The exact nature of the catalyst remains elusive, though a vanadium oxo species is the expected precursor. This uncertainty is typical of heterogeneous catalytic processes in which mechanistic studies are generally difficult. 5 In nature, enzymes utilize metal-oxo moieties in which the reaction center is embedded in a protein matrix. Though the protein is important in the enzyme's biological activity and stability, understanding the chemistry of the reaction site is thus more challenging. One example is cytochrome P-450 which catalyzes important biological processes such as steroid metabolism and drug detoxification. Cytochrome P-450 contains an iron heme which has been shown to use either dioxygen or oxygen-transfer reagents to form an iron (V) oxo species. It is this iron moiety which is capable of transferring an oxygen atom to various substrates. The related horseradish peroxidase also employs an oxo species formed from hydrogen peroxide or an alkyl hydroperoxide in its catalytic oxidations. Model systems for both of these enzymes have recently been prepared.6 Examples of oxidations mediated by homogeneous metal-oxo complexes include the cis-hydroxylation of olefins,7 epoxidation of olefins,8 C-H activation of alkanes,9 and oxygen transfer reactions.lO (Figure 1) Figure 1. Representative examples of homogeneous oxidation reactions. Os04 + Q ;-(~H \.__/OH M=Fe, 0 PhiO M=Mn, 0 PhiO While a metal-oxo bond is intimately involved in the formation of the diols, the epoxidations and C-H activation reactions by the iron and manganese porphyrins are postulated to employ high oxidation state metal-oxo species. These two porphyrin complexes model the iron (V) oxo heme species of cytochrome P-450. 6 Homogenous reactions with imido complexes have been prepared for the oxyamination of olefins,11 azirdinations12 and imide exchange of carbodiimides.13 Figure 2. Representative examples of homogeneous metal imido mediated reactions. R 1. / 2. LAH/ H 20 tBuHN)-/OH R R =Me, Et Ts I Cu(acac) 2 (cat) Phi=NTs acac = acetylacetonate Ts = para-toluenesulfonyl Cl4 W=NPh CyN =C=NCy N d Cl 4W = NCy + PhN = C = NCy Cy=-D In summary both the oxo and imido metal complexes exhibit the ability to mediate important reactions. Chapters 2 and 3 present the preparation of oxo and imido complexes of an early transition metal. These compounds contain a basic heteroatom group (oxo or imido) attached directly to an electrophilic metal center. Chapter 4 presents the synthesis of electrophilic zirconium borollide complexes with a basic amine group that is not coordinated to the metal. 7 References 1. (a) Crabtree, R. H. The Organometallic Chemistry of the Transition Metals. John Wiley and Sons. New York, 1988. (b) Collman, J. P.; Hegedus, L. S.; Norton, J. R.; Finke, R. G. Principle and Applications of Organotransition Metal Chemistry . University Science Books. Mill Valley, California, 1987. 2. For a discussion on the lack of late metal transition metal oxo complexes, see: Mayer, J. M . Comments lnorg . Chern. 1988, 8, 125. 3. (a) Backvall, J. E.; Akermark, B. Ljunggren, S. 0. f. Am. Chern. Soc. 1979, 101, 2411. (b) Stille, J. K.; Divakaruni, R. f. Organomet. Chern . 1979, 169, 239. 4. (a) Maata, E. A.; Du, Y.; Rheingold, A. L. f. Chern. Soc., Chern. Commun. 1990, 756. (b) Maata, E. A .; Du, Y. f. Am. Chern . Soc. 1988, 110, 8249. (c) Rhodes, L. F.; Venanzi, L. M . lnorg . Chern. 1987, 26, 2692. (d) Chan, D. M. -T.; Fultz, W. C.; Nugent, W . A.; Roe, D. C.; Tulip, T. H. f. Am. Chern . Soc. 1985, 107, 251. 5. Centi, G .; Trifori, F.; Ebner, J. R.; Franchetti, V. M . Chern . Rev. 1988, 88, 55. 6. (a) McMurry, T. J.; Groves, J. T. In Cytochrome P-450 Ortiz de Montellano, P. R., Ed.; Plenum: New York, 1986, Chapter 1. 7. (a) Akashi, K.; Palermo, R. E.; Sharpless, K. B. f. Org. Chern . 1978, 43, 2063. (b) Sharpless, K. B.; Williams, D. R. Tetrahedron Letters 1975,35, 3045. 8. (a) see reference 6a (b) White, P. W . Biorganic Chemistry 1990, 18, 440. (c) Gunter, M. J.; Turner, P. Coordination Chemistry Reviews 1991, 108, 115. 9. (a) Groves, J. T .; Kruper, W. J.; Haushalter, R. C. f. Am. Chern. Soc. 1980, 102, 6375. (b) Hill, C. L.; Schoudt, B. C. f. Am. Chern. Soc. 1980, 102, 6374. (c) Groves, J. T.; Nemo, T. E.; Myers, R. S. f. Am. Chern. Soc. 1979, 101, 1032. 10. Holm, R. H . Chern. Rev. 1987, 87, 1401. 11. (a) Sharpless, K. B.; Patrick, D. W.; Truesdale, L. K.; Biller, S. A. f. Am. Chern. Soc . 1975, 97, 2305. (b) Patrick, D. W .; Truesdale, L. K.; Biller, S. A.; Sharpless, K. B. f. Org. Chern. 1978, 43, 2628. (c) Herranz, E.; 8 Sharpless, K. B. f. Org. Chern. 1978, 43, 2544. (d) Herranz, E.; Biller, S. A.; Sharpless, K. B. f . Am. Chern . Soc. 1978, 100, 3596. 12. (a) Allain, E. J.; Hager, L. P.; Deng, L.; Jacobsen, E. N . f. Am. Chern . Soc . 1993, 115, 4415. (b) Perez, P . J.; Brookhart, M.; Templeton, J. L. Organometallics 1993, 12, 261. (c) Evans, D. A.; Faul, M . M .; Bilodeau, M . T .; Anderson, B. A.; Barnes, D. M . f . Am. Chern . Soc . 1993, 115, 5328. (d) Evans, D. A.; Faul, M . M .; Bilodeau, M. T. f. Org. Chern. 1991, 56, 6744. (e) Mahy, J.-P.; Bedi, G.; Battioni, P.; Mansuy, D. f. Chern. Soc., Perkin Trans. 1988, 22, 1517. 13. Meisel, I.; Hertel, G.; Weiss, K. f . Mol. Catal. 1986, 36, 159. 9 Chapter 2 Cationic Tantalum Oxo Complexes ABSTRACT ....................................................... .......................... 10 INTRODUCTION ....................................................................... 11 RESULTS AND DISCUSSION .. ..... ......... .... ... ............. .. ... ... .... 18 CONCLUSION ............................................................................ 25 EXPERIMENTAL ............ ............................................................ 26 REFERENCES .............................................................................. 31 APPENDIX 1 ............................................... .. .. ............. ...... .... .... .. 34 10 The preparation of the reactive tantalum cation, [Cp*2Ta=O] + will be discussed. Metathesis of Cp*2Ta(=O)Cl with AgPF6 or TlPF6 afforded [Cp*2TaF2][PF6], which presumably formed from P-F activation of the counterion. When S03CF3-, a better non-coordinating anion, was used, Abstract: [Cp*2Ta(=O)][S03CF3] was isolated. However, this cation was unreactive toward styrene, methane, or benzene, but exposure to water resulted in the 1,2-addition product, [Cp*2Ta(OHh][S03CF3] . Finally, treating Cp*2Ta(=O)H with [Ph3C][B(C6fs)4] afforded [Cp*2Ta(=O)][B(C6Fs)4]. Even with this noncoordinating counterion, the complex was found to be surprisngly unreactive. ll Introduction Recent interest in the synthesis and reaction chemistry of metal ligand multiple bonds has been sparked by the successful modeling of some of the reactions described in Chapter 1.1 The lack of reactivity of many early transition metal-oxo complexes lies in the propensity of these metal-oxo bonds to assume triple bond character. 8- 0+ LnM=o: - - - L nM=O •• 1 n Comparing the potential reactivities of the two resonance forms, the oxygen atom of II is expected to be more nucleophilic and the metal center of II is expected to be more electrophilic than in I. Design of reactive early transition metal oxo complexes should therefore, included features that strongly favor resonance form II. Since the oxo ligand generally manifests maximal rc-bonding to a metal, complexes intended to exhibit resonance II's character are formidable design challenges. Recently, Wigley2 introduced the term "re-loaded" to describe situations in which the number of potential rc interactions with the ligands exceed the capacity of the metal, resulting in a formal electron count exceeding eighteen on the metal. Two such complexes are (OC)W(RC=CR)3 and Os(=NR)3. The inertness of these "20 electron" complexes is attributed to the "extra" lone pair residing on a ligand-based molecular orbital.3,4 Due to their electronic properties, the bent metallocenes provide a unique opportunity to study metal-oxo bond that have little triple bond character. As described by Hoffmann,S the cyclopentadienyl-metal bond is comprised of one cr and two rc interactions with three frontier orbitals located in the wedge between the cyclopentadienyl rings. The la1 molecular orbital is a dz2-like orbital; the b2 molecular orbital is a dxz orbital; and the 2a1 molecular orbital is a px-s hybrid-like orbital (Figure 1). 12 Figure 1. Frontier molecular orbitals of bent metallocenes. An oxo or imido ligand forms one cr bond with the 2a1 orbital and one 1t bond with the b2 orbital. However, the orbital from the oxygen or nitrogen that is available for a second 1t bond is orthogonal to the la1 orbital. For this reason , oxo or imido groups will be two electron donors in bent metallocene complexes with one (imido) or two (oxo) lone pairs residing on the heteroatom. Bent metallocene oxo complexes, therefore, will ideally fulfill our design of a complex with resonance form II character. For a d2 bent metallocene, the lone pair of electrons are localized in the la1 orbital and the metal is expected to be nucleophilic. Indeed, Geoffroy has shown that the d2 tungsten metallocene complex, Cp2W=O (1),6 undergoes formal [2+2] addition reactions with carbonyl groups, ketenes and isocyanates (Scheme !).7 Scheme I 2 1 .,......OXCF3 cp 2w......._ 0 CF3 4 13 Though the mechanism of the reaction is unknown, the conversion of the oxo complex (1) to the metallacycle (3) may proceed either by a concerted [2+2] cycloaddition through the transition state A or by nucleophilic attack of the oxo moiety to form B followed by ring closure (Scheme II). Scheme II 1 / 3 B Interestingly, the only cycloaddition product observed with phenylisocyanate is that with a W-N bond. This result implies either a preference for transition state A or W-N bond formation from the closure in B. Both of these processes result in the reduction of bond order for the C=N bond, which is weaker than the C=O bond. Previous work in this group8 has shown that the d2 complex Cp""2 W =0 (6) also contains a reactive oxo group. The W=O bond stretch occurs at 860 cm-1, indicative of a weak metal oxo bond. Typical metal-oxo stretches range from 800-1000 cm-1, so this tungsten-o~o bond stretch is indicative of a low W=O bond order. The lack of triple bond character and, thus, nucleophilicity at the oxygen atom is borne out in the reactivity of the complex which reacts with TMSCl and HBF4 to afford 7 and 8 respectively. (Scheme III) 14 Scheme III ~I ~Cl KOH 5 ~ ~ TMSCl ~TMS ~Cl 6 7 H 180 2 8 9 Interestingly, 6 undergoes oxo-exchange with labelled water. The reaction proceeds by a 1,2-addition/ elimination pathway via the dihydroxide intermediate. The syntheses of early transition metal reactive d0 metal oxo, imido,9 alkylidene, 10 phosphido,11 and sulfido 12 complexes have been achieved. These electrophilic complexes are expected to encourage cr coordination of the substrate prior to its reaction.13 Recently, Bergman 14 has provided evidence for the transient 16 electron intermediate [Cp*2Zr=Ol (12) by the thermolysis of Cp*2Zr(OH)Ph (10) or the deprotonation of Cp*2Zr(OH)(OS02CF3) (11). 15 Evidence of its intermediacy is provided by trapping 12 with either a nitrile or acetylene. (Scheme IV) Scheme IV ,.......OH ~ C p*2Zr . . . _ ---=------.Ph -C6H 6 10 0 Cp*2Zr(":>-R' ---rearranged ""f'" products R" 14a, R'= R"=Ph 13 b, R'= Me, R"=Ph In the presence of benzonitrile, the observed product is a six-membered metallacycle (13), which presumably arises from an initial cycloaddition step followed by the insertion of a second equivalent of the nitrile. Substituted acetylenes afford an oxametallacycle (14), which rearranges when heated at higher temperatures. Parkin 15 has confirmed this claim by preparing Cp*2Zr(=O)(NCsHs) (15) from the oxidation of Cp*2Zr(C0)2 with N20 in pyridine; 15 was found to undergo similar [2+2] cycloaddition chemistry. The crystal structure of the related (115-CsMe4Et)2Zr(O)(NCsHs) shows a Zr=O bond length of 1.80 A, which is shorter than other Zr-0 single bonds. The infrared absorption of 780 cm-1 is low in energy for metal-oxo bonds and indicates a bond with very little triple bond character. 16 Scheme V ~H - -H- -=2-0_-~ _N_H. . :2.P_h-~H ~H ~C5H5 ~HPh 16 15 17 < Zr.::::;;--- ~CsH.'Bu 18 Furthermore, 15 readily undergoes 1,2-addition chemistry with water and aniline across the reactive metal-oxo bond to afford the dihydroxy (16) and hydroxyamido (17) complexes. Interestingly, the pyridine adduct (18) is labile to substitution by other Lewis bases such as 4-tert-butylpyridine, suggesting the formation of [Cp,..2Zr=Ol as an intermediate from the dissociation of pyridine. In another example of 1,2-addition, the complex Cp,..zTa(= 180)H was found to undergo exchange of the oxo group with Dz160 without exchange of the hydride group.16 180 Cp,.. T/ + D 160 2 ' H 2 17 The oxygen exchange reaction does not proceed by initial a-migration to form [Cp*2TaOH] followed by the oxidation addition of water since this would also necessarily involve exchange of the hydride on Cp*2Ta(=O)H. While Bergman has demonstrated that the transient [Cp*2Zr=OJ undergoes [2+2] addition with diphenylacetylene and isocyanates, the isoelectronic [Cp2Zr=NtBu] fragment activates the C-H bond on benzene (see Chapter 3). Since the two complexes also differ in their ancillary ligand, one with Cp and the other with Cp*, direct comparisons of the two complexes are difficult. For this reason we have been interested in studying the reactivity of both the [Cp*2Ta=O]+ and [Cp*2Ta=NR)+ cations. With a formal positive charge on the metal, the cations are expected to be more reactive. This chapter presents the efforts in the synthesis of the [Cp*2Ta=OJ+ species. 18 Results and Discussion The preparation of a [Cp*2Ta=O]+ species was attempted by two strategies: (1) metathesis of chloride from Cp*2Ta(=O)Cl with silver salts and (2) hydride abstraction from Cp*2Ta(=O)H by a trityl salt. Scheme VI + Cp* 2Ta(=O)Cl + AgX ~ X Cp"2Ta(~O)H Ph3CX~ + The choice of the counterion, x-, is expected to be crucial since a coordinating anion is anticipated to reduce the reactivity while a non-coordinating anion should result in a maximally reactive species. Indeed, it might be too unstable to isolate.17 In order to investigate the metathesis reactions, an efficient synthetic route to Cp*2Ta(=O)Cl was needed. Previous work in this group has demonstrated that Cp*2Ta(=O)Cl can be prepared in low yield from Cp*2TaCl2 and hydrogen peroxide.18 Substituting iodosylbenzene for H202 afforded an alternate route to Cp*2Ta(=O)Cl in high yield. When Cp*2TaCl2 was added to a THF solution of iodosylbenzene over 1% sodium amalgam; the yield of Cp*2Ta(=O)Cl was 75%.19 Na / Hg, PhiO THF Cp*2Ta(=O)Cl 19 Initial metathesis reactions with silver tetraphenylborate resulted in complex mixtures of products. Hexafluorophosphate was predicted to be an innocent counterion (one not expected to interact with the tantalum center). To test this prediction, Cp*2Ta(=O)Cl was treated with thallium hexafluorophosphate. A yellow solid was isolated in less than 50% yield and it was crystallographically determined to be [Cp*2TaF2HPF6] (20) (Figure 2). 19 + Cp* 2Ta(=O)Cl + TlPF6 20 Presumably, [Cp*2Ta=O][PF6] was transiently formed by the metathesis of Cp*2Ta(=O)Cl, but subsequent P-F activation of the counterion by the highly electrophilic cation produced [Cp*2TaF2][PF6].20 In order to circumvent this problem, triflate was the next logical counterion to try. Treatment of Cp*2Ta(=O)Cl with AgS03CF3 afforded a solid, [Cp*2Ta(=O)](S03CF3], 21, which was spectroscopically characterized. + 21 The complex is surprisingly soluble in benzene, methylene chloride, and tetrahydrofuran, suggesting that 21 dissociates in polar solvents and remains undissociated in nonpolar solvents. When the complex was prepared in tetrahydrofuran, [Cp*2Ta(=O)(THF)](S03CF3] was isolated but the solvent was easily removed by heating the solid in vacuo. 20 Figure 2. ORTEP diagram of [Cp""2TaF2JPF6 (20) 21 While growing crystals of 21, two different types of crystals were observed and both were determined by X-ray crystallography.21 The ORTEP diagrams for both crystalline products (22 and 23) are shown in figures 3 and 4. ~H ~H + S0 3CF 3 22 ~H ~ Tcf' + S03 CF3 - 23 Complex 22 is the expected product from the 1,2- addition of H20 across the Ta=O moiety of [Cp*2Ta(=O)](S03CF3]. Water in the solvent during crystallization accounts for the isolation of 22. On the other hand, 23 is probably the result of Cp*2Ta(=O)Cl reacting with minute amounts of HS03CF3 present during the generation of 21 . This protonation reaction has been demonstrated independently. When Cp*2Ta(=O)Cl was treated with HS03CF3, the product was determined to be [Cp*2Ta(OH)(Cl)](S03CF3] (23) by its 1H NMR spectrum. [Cp*2Ta(OH)(Cl)t[S03CF3f 23 This protonation of the Ta=O bond is reversible, since treatment of 23 with triethylamine cleanly affords Cp*2Ta(=O)Cl. Though reactive with water and HS03CF3, 21 undergoes cycloaddition chemistry with neither styrene nor C-H activation of methane or benzene. As revealed in the crystal structures of both 22 and 23, the triflate anion hydrogen bonds with the hydroxyl group of the cation portion of the complex, indicating that triflate is not a completely innocent counterion and may be coordinated to the tantalum center in 21 . A coordinate triflate in 21 would reduce its reactivity toward substrates. 22 0 23 Figure 4. ORTEP diagram of [Cp*2Ta(OH)(Cl)](S03CF3] (23) 24 The search of a truly innocent counterion continued with perfluorotetraphenylborate.22 Treatment of Cp*2Ta(=O)H with [Ph3C](B(C6Fs)4] in benzene afforded a green solid that exhibits an IR stretch at 980 cm-1, which is indicative of a Ta=O bond. The product has been preliminarily determined to be [Cp*2Ta(=O)][B(C6Fs)4], 24. + 24 This compound was surprisingly unreactive with benzene at 12ooc though the counterion is not expected to be coordinated to the cation. In order to better understand the reaction chemistry of Cp*2Ta(=O)Cl and Cp*2Ta(=NPh)H, the Ta-O and Ta-N bond orders in these complexes were probed. Therefore, the electrochemistry of both oxo and imido complexes were obtained. An irreversible oxidative peak at 1.06 volts (versus SCE) dominates the cyclic voltammogram of Cp*2Ta(=O)Cl in acetonitrile. This result precludes the oxidation of Cp*2Ta(=O)Cl by silver (I). Interestingly, the electrochemistry of Cp*2Ta(=NPh)H and Cp*2Ta(=NPh)I (25) exhibited irreversible oxidative waves at 30 millivolts and 560 millivolts (versus SCE). This is consistent with the oxidation of both complexes with Ag+ salts. The electrochemistry and solution chemistry results are both in agreement with a molecular orbital representation in which the second lone pair of the nitrogen is not strongly bonded to the tantalum center. In addition, the photoelectron spectroscopy23 of Cp*2Ta(=O)X (X= H, Cl, CH3, Ph, OCH3) and Cp*2TaC=NPh)Y (Y = H, I) support a molecular orbital description in which the second metal-7t interaction for the [Cp*2Ta=X]+ fragment contains anti-bonding character. This molecular orbital is much higher in energy in the imido complexes when compared to the metal-oxo orbital and is consistent with the reactive nature of the imido ligand in the [Cp*2Ta=X] + fragment. 25 Conclusion During the preparation of [Cp*2Ta=O]+, the counterion has been found to be crucial to its isolation. With PF6-, P-F bond activation led to the isolation of [Cp*2TaF2lPF6. Triflate anion proved to be less problematic. [Cp*2Ta=O][S03CF3] was isolated from the metathesis reaction, though the 1,2addition of water to afford [Cp*2Ta(OH)2][S03CF3] was a significant side reaction. Finally, when Cp*2Ta(=O)H was treated with [Ph3C][B(C6F5)4], [Cp*2Ta=O][B(C6Fs)4] was isolated and found to be surprisingly unreactive. These results agree with other findings that oxo complexes tend to be much less reactive than the isostructural imido complexes.24 The strong metal-oxo bond undoubtedly accounts for the observed inertness of these compounds. 26 Experimental General Considerations. All manipulations were performed using glovebox or high vacuum line techniques.25 Solvents were dried over LiAlH4 or Na / benzophenone and stored under vacuum over "titanocene."26 Benzene-d6 , tetrahydrofuran-ds, and methylene chloride-dz were dried over activated molecular sieves (4A, Linde) and stored over "titanocene" or Na/ benzophenone. Argon and nitrogen gases were passed over MnO on vermiculite and activated sieves. Iodosylbenzene27 was prepared as previously described. Silver triflate and thallium hexafluorophosphate were purchased from Aldrich and used without further purification. Many reactions were surveyed by NMR spectroscopy. Any experiment described herein but not explicitly listed below was carried out in a sealed NMR tube using -0.7 mL of the NMR solvent with the appropriate reagents. Cp*2Ta(=0)Cl (19). A large high pressure glass reaction vessel was charged with 2.5 g (11 mmol) iodosylbenzene, 25.9 g of 1% sodium amalgam, and 5.01 g (9 mmol) Cp*2TaCl2. Approximately 100 mL THF was then condensed on the solids at -780C. The reaction vessel was agitated for three days with the resultant solution appearing grayish white. The solution was filtered through Celite to remove the mercury and then transferred to a 100 mL round bottom flask equipped with a swivel frit assembly. The volatiles were removed in vacuo. Toluene was then condensed on the solid and the suspension was filtered to afford (3.48 g, 6.92 mmol) a white solid, 29. Yield = 77%. [Cp"'2TaF2]PF6 (20). A high pressure glass reaction vessel was charged with 460 mg (0.92 mmol) Cp*2Ta(=O)Cl and 320 mg (0.92 mmol) TlPF6. Approximately 20 mL of methylene chloride was condensed on the solids at -78°C and the resultant solution was heated at 8ooc for three days. The violet solution was then transfered to a 100 mL round bottom flask fitted with a swivel frit assembly. A white solid was filtered and the filtrate was concentrated. Toluene was added to the solution and filtration afforded 267 mg (0.42 mmol) of a yellow solid, 20. Yield= 46%. Analysis : Calculated (Found) C: 37.87 (37.50); H : 4.77 (4.70). 27 [Cp*2Ta=OUS03CF3] (21). A 50 mL round bottom flask was charged with 903 mg (1.80 mmol) Cp*2Ta(=O)Cl and 462 mg (1.80 mmol) silver triflate. A swivel frit assembly was attached and approximately 40 mL methylene chloride was condensed on the solids at -78°C. The resultant solution was allowed to warm slowly to room temperature and then stirred for 90 minutes. Filtration of a gray solid yielded an orange filtrate from which the volatiles were removed in vacuo. The solid was washed with petroleum ether to afford 468 mg (0.76 mmol) of a light brown solid, 21 . Yield = 42%. IR spectroscopy (KBr, cm-1): 1271.6, 1143.7, 1160.4, 1031.7, 980.3, 856.0, 637.1. Analysis: Calculated (Found) C: 40.91 (38 .79); H: 4.91 (4.60). [Cp*2Ta(=O)][B(C6Fs)4] (24). A 50 mL round bottom flask was charged with 200 mg (0.43 mmol) Cp*2Ta(=O)H and 394 mg (0.43 mmol) [Ph3C][B(C6Fs)4) and a swivel frit assembly was attached. Approximately 20 mL benzene was condensed on the solids at -78°C, and the solution was stirred at room temperature overnight. The volatiles were removed in vacuo and the solid was washed with petroleum ether to afford 355 mg (0.31 mmol) of a light green solid. Yield= 73%. IR spectroscopy (KBr, cm-1 ): 1513.0, 1463.9, 1085.9, 979.9, 774.7, 756.2, 684.1, 669.7. IR spectroscopy (nujol mull, cm-1 ): 1634.3, 1513.9, 1275.3, 1084.7, 979.7, 774.2, 756.0, 684.0, 661.4. Analysis: Calculated (Found) C: 46.10 (48.91); H : 2.64 (3.26). Cp*2Ta(=NPh)l (25). A high pressure glass vessel was charged with 795 mg (1.46 mmol) Cp*Ta(=NPh)H . Approximately 75 mL toluene was condensed onto the solid at -780C. Methyl iodide (250 j.!L, 4.02 mmol) was added via syringe against an argon flow. The reaction vessel was heated at 80°C for 48 hours, resulting in a red solution with a small amount of solid. This solution was transferred to a round bottom flask equipped with a swivel frit assembly. The solution was then concentrated and petroleum ether was added. Filtration afforded 701 mg (1.05 rnrnol) of 25 as an orange solid. Yield = 72 %. IR spectroscopy (nujol mull, cm-1): 1161.4, 1063.4, 1019.2. Analysis: Calculated (Found) C: 46.65 (46.51); H: 5.27 (5.41); N: 2.09 (1.80). 28 X-Ray Crystal Structure Determination of [Cp"'2TaF2JPF6 (20). The ORTEP drawing of [Cp"'2TaF2lPF6 is shown in figure 2. A yellow crystal was mounted in a greased capillary and then centered on a CAD-4 diffractometer. Unit cell parameters and an orientation matrix were obtained by a least squares calculation from the setting angles of 25 reflections with 15° < e < 17°. The data were corrected for absorption. Coordinates of the tantalum atom were obtained from a Patterson map; locations of the other non-hydrogen atoms were determined from successive structure factorFourier calculations. Calculations were performed with programs of the CRYM Crystallographic Computing System and ORTEP. Scattering factors and corrections for anamalous scattering were taken from a standard reference.28 Electrochemistry of Cp"'2Ta(=O)Cl, Cp"'2Ta(=NPh)H and Cp"'2Ta(=NPh)l. The electrochemical results were obtained on a BAS 100A Electrochemical Analyzer using two compartment sample cells. All the experiments were performed under an argon or nitrogen atmosphere utilizing a Ag+ I AgCl reference electrode and platinum gauze as an auxiliary electrode. For a typical experiment, 4-6 mg of the complex was added with approximately 340 mg of tert-butylammonium perchlorate or tertbutylammonium hexafluorophosphate. The Cp"'2Ta(=O)Cl data were acquired in acetonitrile while the Cp"'2Ta(=NPh)H and Cp"'2Ta(=NPh)I data were acquired in THF. 29 T abl e I . lH NMR S>pectra1 D ata f or compJ exes 19 - 25 Assignment 8 (ppm) Cs(CH3)5 1.85 (s) [Cp*2TaF2lPF6 (20) in CD2Cl2 Cs(CH3)5 2.23 (s) [Cp*2TaF2lPF6 (20) in THF-ds Cs(CH3)5 2.28 (s) [Cp*2Ta=OlS03CF3 (21) in CD2Cl2 Cs(CH3)5 2.04 (s) [Cp*2Ta=O]S03CF3 (21) Cs(CH3)5 1.78 (s) Cs(CH3)5 2.18 (s) Compound Cp*2Ta(=O)Cl (19) J (Hz) in C6D6 in C6D6 [Cp*2Ta=O]B(C6Fs)4 (24) in THF-ds 10.92 13.05 Cp*2Ta(=NPh)I (25) in THF-ds Cs(CH3)5 para-Cr,Hs ortho-C6Hs meta-C6H_5 2.08 (s) 6.33 (t) 7.20 6.40 (d) 7.50 6.90 (t) 7.50 T a ble II. 19p NMR S'pectra1 Data f or comp exes 20 - 24 Assignment 8 (p__Qm) [Cp*2TaF2lPF6 (20) in CD2Cl2 Ta-F 23.57 P-F 73.20 [Cp*2TaF2lPF6 (20) in THF-ds P-F 18 Ta-F -73.96 [Cp*2Ta=O]S03CF3 (21) CF3 -76.92 CF3 -77.19 Compound in CD2Cl2 [Cp*2Ta=OlS03CF3 (21) in CoD6 [Cp*2Ta=O]B(C6Fs)4 (24) in THF-ds -129.51 -161.87 -165.35 J (Hz) 707 707 30 T a bl e III 13C NMR S'2_ectra1 D ata f or comp. exes 19 - 25 Assignment 8 (EQ_m) Cp*2Ta(=O)Cl (19) Cs(CH3)5 in C606 Cs(CH3)5 11.31 129.24 [Cp*2TaF2JPF6 (20) Cs(CH3)5 10.72 in CD2Cl2 Cs(CH3)5 129.53 [Cp*2Ta=OJS03CF3 (21) Cs(CH3)5 Cs(CH3)5 11.51 Compound in CD2Cl2 [Cp*2Ta=O]S03CF3 (21) in C6D6 [Cp*2Ta=O]B(C6Fs)4 (24) in THF-ds 122.58 11.24 Cs(CH3)5 Cs(CH3)5 121.15 11.12 121.14 Cs(CH3)5 Cs(CH3)5 aromatic aromatic 135.49 137.68 aromatic 138.75 140.75 aromatic aromatic 147.52 150.83 aromatic Cp*2Ta(=NPh)I (25) in THF-ds 13.33 Cs(CH3)5 aromatic aromatic 117.40 118.14 118.95 128.44 160.28 Cs(CH3)5 aromatic aromatic T abl e IV . 31p NMR S,pectra1 D ata f or comp. ex 20 Assignment 8 (p_Qm) J (Hz) [Cp*2TaF2]PF6 (20) PF6 in CD2Cl2 PF6 18 110.65 713 Compound 31 References 1. (a) Nugent, W. A.; Haymore, B. L. Coord. Chern . Rev . 1980,31, 123. (b) Nugent, W. A.; Mayer, J. M. Metal- Ligand Multiple Bonds, John Wiley and Sons, New York, 1988. 2. Huber, S. R.; Baldwin, T. C.; Wigley, D. E. Organometallics 1993, 12, 91. 3. (a) Tate, D. P.; Augl, J. M.; Ritchey, W . M.; Ross, B. L.; Grasselli, J. G. f. Am. Chern. Soc . 1964, 86, 3261. (b) Tate, D. P.; Augl, J. M. f. Am. Chern. Soc . 1963,85,2174. 4. Schofield, M. H.; Kee, T. P.; Anhaus, J. T.; Schrock, R. R.; Johnson, K. H.; Davis, W . M . lnorg. Chern. 1991,30, 3595. (b) Anhaus, J. T.; Kee, T. P.; Schofield, M . H .; Schrock, R. R. f. Am. Chern . Soc . 1990, 112, 1642. 5. Lauher, J. W.; Hoffmann, R. f. Am. Chern . Soc. 1976, 98, 1729. 6. Green, M. L. H .; Lynch, A . H.; Swan, M . G. f. Chern . Soc. , Dalton Trans. 1972, 1445. 7. (a) Pilato, R. S.; Housemekerides, C. E.; Jernakoff, P.; Rubin, D.; Geoffroy, G. L.; Rheingold, A . L. Organometallics 1990, 9, 2333. (b) Jernakoff, P.; Geoffroy, G . L.; Rheingold, A . L.; Geib, S. J. f. Chern. Soc ., Chern. Commun. 1987, 1610. 8. Parkin, G.; Bercaw, J. E. Polyhedron 1988, 7, 2053. 9. See introduction of Chapter 3. 10. (a) Fryzuk, M. D.; Mao, S. S. H .; Zaworotko, M. J.; MacGillivray, L. R. f. Am. Chern . Soc. 1993, 115, 5336. (b) Fryzuk, M. D.; Mao, S. S. H .; Zaworotko, M. J.; MacGillivray, L. R. Abstract 293. 206th National ACS Meeting, Chicago, Illinois, 1993. (c) Finch, W. C.; Anslyn, E. V.; Grubbs, R. H. f. Am. Chern. Soc. 1988, 110, 2406. (d) Howard, T. R.; Lee, J. B.; Grubbs, R. H. f. Am. Chern. Soc. 1980, 102, 6876. (e) Tebbe, F. N.; Parshall, G. W .; Reddy, G . S. f. Am. Chern . Soc . 1978, 100, 3611. 11. (a) Hou, Z.; Breen, T. L.; Stephan, D. W. Organometallics 1993, 12, 3158. (b) Ho, J.; Hou, Z .; Drake, R. J.; Stephan, D. W. Organometallics 1993, 12 , 3145. (c) Ho, J.; Hou, Z.; Drake, R. J. Stephan, D. W. Abstracts 72 and 74. 206th ACS National Meeting, Chicago, Illinois, 1993. (d) Hou, Z.; Stephan, D. W. f. Am. Chern. Soc. 1992, 114, 10088. 12. (a) Brunner, H.; Kubicki, M. M.; Leblanc, J-C.; Moise, C.; Volpato, F.; 32 Wachter, J. f. Chern. Soc ., Chern. Commun. 1993, 851. (b) Nelson, J. E.; Parkin, G .; Bercaw, J. E. Organometallics 1992,11, 2181. 13. Crabtree, R. H. Angew. Chern. Int. Ed . Engl. 1993, 32 , 789. 14. (a) Carney, M. J.; Walsh, P. J.; Hollander, F. J.; Bergman, R. G. Organometallics 1992, 11, 761. (b) Carney, M. J.; Walsh, P. J.; Bergman, R. G. f. Am . Chern . Soc . 1990, 112, 6426. (c) Carney, M . J.; Walsh, P. J.; Hollander, F. J.; Bergman, R. G. f. Am. Chern . Soc. 1989, 111 , 8751. 15. Howard, W. A.; Waters, M.; Parkin, G. f. Am . Chern . Soc. 1993, 115, 4917. 16. Parkin, G .; Bercaw, J. E. f. Am . Chern. Soc. 1989, 111, 391. 17. Strauss, S. H . Chern . Rev. 1993, 93, 927. 18. van Asselt, A., Ph. D. Thesis, California Institute of Technology, 1987. 19. For a better synthesis of Cp*2Ta(=O)Cl see: Antonelli, D. M .; Schaefer, W . P.; Parkin, G .; Bercaw, J. E. Submitted manuscript to f. Organomet . Chern. 20. Jordan, R. F.; Dasher, W. E.; Echols, S. F. f. Am . Chern . Soc. 1986,108, 1718. 21. Quan, R. W.; Bercaw, J. E.; Schaefer, W . P. Acta. Cryst . 1991, C47, 2057. 22. (a) Lambert, J. B.; Zhang, S.; Stern, C. L.; Huffman, J. C. Science 1993, 260, 1917. (b) Hlatky, G . G .; Turner, H . W .; Eckman, R. R. f. Am . Chern . Soc. 1989, 111, 2728. (c) Turner, H. W. European Patent Application 1988 2 77 004. (d) Hlatky, G . G .; Turner, H. W. European Patent Application 1988 277 003. (e) Chien, J. C. W .; Tsai, W-M.; Raush, M . D. f. Am. Chern . Soc . 1991, 113 , 8570. (f) Xinmin, Y.; Stern, C. L.; Marks, T. J. f. Am. Chern . Soc . 1991, 113, 3623. 23. Wright, I. N.; Ph. D. thesis, Brasenose College, Oxford, 1991. 24. Antonelli, D. M .; Blake, R. E.; Bercaw, J. E. Unpublished results. 25. Burger, B.J.; Bercaw, J. E. In Experimental Org anometallic Chemis try ; Wayda, A. L., Darensbourg, M . Y. Eds.; ACS Symposium Series 357; 33 American Chemical Society, Washington, D. C. 1987. 26. Marvich, R. H .; Brintzinger, H . H . f. Am. Chern . Soc. 1971, 93, 2046. 27 Haltzman, H .; Sharefkin, J. G. Organic Synthesis vol. 43, 60. 28. International Tables for X-ray Crystallography, Volume IV, p. 71, p . 147; Birmingham, Kynoch Press, 1974. 34 Appendix 1. X-ray crystal structure data for [Cp*2TaF2HPF6l (20). Table V. Crystal and Intensity Collection Data for [Cp*2TaF2HPF6l (20). chemical formula crystal dimension, mm crystal system space group a,A b,A c, A p, deg · V, A3 C3oH3oFgTa all dimensions < 0.7 mm monoclinic P21 / c 11.582 (5) 12.514 (6) 15.712 (6) 90.34 (3) 2277.2 (17) Peale, g cm- 3 1.850 z 4 A.,A 0.711 !l, cm-1 52.33 23 temp, °C 28 rang, deg no. of reflections measured, total 3-50 3996 R 0.053 GOF 2.65 35 Table VI. Final Heavy Atom Parameters for [Cp•2TaF2HPF6l (20). :z:, y, z and Ueq" X 104 Atom :z: y z Ta 7753(.4) 2672(.3) 4843( .3) 417(1) F1 7052(8) 2373(6) 3776(5) 1109(28) F2 9122(6) 3342(6) 4484(6) 1191(30) Cp1 6394(9) 4120(8) 4590(7) 492(27) Cp2 7333(10) 4592(8) 4953(8) 591(33) Cp3 7504(11) 4137(9) 5793(8) 645(34) Cp4 6557(9) 3457(9) 5943(7) 507(27) CpS 5914(9) 3423(9) 5196(7) 518(27) Cp6 7442(9) 980(8) 5594(8) 500(28) Cp7 7707(10) 725(8) 4 714(8) 565(32) CpS 8862(9) 1073(7) 4574(7) 456(26) Cp9 9315(8) 1503(8) 5330(7) 448(25) Cp10 8452(9) 1461(8) 5953(6) 468(25) Mel 5921(11) 4371(10) 3736(8) 717(36) Me2 8165(13) 5409(10) 4552(11) 993(50) Me3 8438(13) 4493(12) 6425(10) 973( 47) Me4 6162(12) 3137(12) 6822(8) 844(41) Me5 4775(10) 2857(11) 5060(10) 822( 40) Me6 6381(12) 565(11) 6031(9) 853( 41) Me7 6920(12) 159(11) 4110(9) 878(42) Ueq 36 Table VI. (Continued) Atom y z Me8 9500(11) 990(10) 3747(8) 736(37) Me9 10521(10) 1893(10) 5451(9) 713(34) Me10 8677(11) 1620(11) 6899(8) 771(39) p 12667(3) 2420(3) 2766(2) 580(7) F3 13308(10) 3482(9) 2883(9) 1740(47) F4 12943(10) 2434(10) 1767(7) 1583( 44) F5 13811(9) 1820(10) 2942(7) 1586( 40) F6 11531(8) 3067(10) 2600(8) 1729( 44) F7 12007(10) 1342(9) 2637(8) 1735( 47) F8 12381(9) 2352(12) 3705(7) 1786(50) 37 Table VII. Anisotropic Displacement Parameters for [Cp•2TaF2HPF6l (20) . Atom Uu U·n ull U12 ull Ta F1 F2 Cp1 Cp2 Cp3 Cp4 CpS Cp6 Cp7 Cp8 Cp9 Cp10 Mel Me2 Me3 Me4 Me5 Me6 Me7 Me8 Me9 Me10 556( 3) 374(3) 323(2) 119(2) 69(2) 909 56 575 69 71 777 91 474 65 466 63 518 69 678 76 574 67 715 52 515 66 1959 96 386 59 358 42 -50 53 793 59~ -30 52 102(69) 506 71 536 67 549 355 58 313 55 288 52 651 81 512 67 298 63 137 52 -156~69) 629 74 704 86 505 63 543 66 775 89 449 760 90 1148 121 1047 105 845 995 105 888~103) 14 47 84 59 46 45) 151 116(69 -59(76) 181(88) 327(89) 81 57 5(67) 35(53) -21(50) -96(50) -116(69) -28(106) -431(100) 184(72) 83(73) 302(82) -338(88) 213(72) p F3 F4 F5 F6 F7 F8 1802t3l 94rl 316n rl 68l 447n 361r4) 60~ 1032rlll 482r9) 106~ 57ln 62rl -540!53) 74rl 164n 538n 9rl -17~53~ 55~ 537t6) -5~ 50~ 410 59) 616 81) 1465(146~ 920(113 492(73) 554n 815 97l 1026r08l -24~68~ 724~92 -221~75~ 804 94 888 98 937 99 10 75 943 109 1019 113 594 81) 144 71 921~96) -48~63) 947 98 548 16 678 84 617~75) 888 101) 648 20) 1560 94 1311 82 2263 1741 105 930 76) 1713 106) -153 86 597(77 1985 117) 1258 80) 1248 91) 3351 191) 1977 136 751 65) -598 83 38(99) 3 54) -25l68) 60rl 79~ 68~ 2526r51) -231~72l 147lt3l 1213~92) 139~ 1170r9) 1894r14) 2113r29l 642~79~ 478 72) 546 18) Ui,j values have been multiplied by 10 308 44 16 9 68 14 -708~100) 291 70) 539(76) -777(85) 555(103) 252(61) [;"23 59( 2 ) -287 ( 40) 684~ 58) -6 49) 36( 53) -182(60) -26( 54) - 29 ( 54 ) 168( 52) 24( 54 ) 31 ( 45 ) 52(48 ) 44( -! 7 ) 47 (67 ) 162 (92 ) -298 (86 ) 38 ( 73 ) -34(87 ) 372 (83 ) -189(82 ) -53( 64 ) 70( 73 ) 122(67 ) -69(15 ) -6(94 ) -27( 76) 786 (91 ) -744(105 ) -307(87 ) -49 (87 ) 4 The form of the displacement factor is: exp -27rl(U11 hla•' + U22 k 2 b•' + U33 f2c•' + 2Uuhka•b• + 2Ullhf.a•c• + 2U2Jkf.b•c• ) 38 Table VIII. Complete Distances and Angles for [Cp•2TaF2] [PF6] (20) . Dista.nce( A) Ta -CpA -CpB Ta Ta -Fl Ta -F2 Ta -Cpl -Cp2 Ta -Cp3 Ta Ta -Cp4 Ta -CpS Ta -Cp6 Ta -Cp7 Ta -CpS Ta -Cp9 Ta -CplO Cpl -Cp2 Cpl -CpS Cpl -Mel Cp2 -Cp3 Cp2 -Me2 Cp3 -Cp4 Cp3 -Me3 Cp4 -CpS Cp4 -Me4 CpS -MeS Cp6 -Cp7 Cp6 -CplO Cp6 -Me6 Cp7 -CpS Cp7 -Me7 CpS -Cp9 CpS -MeS Cp9 -CplO Cp9 -Me9 CplO -MelO p -F3 p -F4 p -F5 p -F6 p -F7 p -FS 2.105 2.119 l.S96(S) l.SS3(S) 2.432(11) 2.457(11) 2.3S3(12) 2.42S(11) 2.396(11) 2.451(11) 2.446(11) 2.416(10) 2.44S(l0) 2.444(10) 1.359(1S) 1.409(1S) 1.4S0(16) 1.4S0(17) l.S42(19) 1.410(16) 1.529(19) 1.3S6(15) l.Sl2(17) l.Sl2(17) 1.454(16) 1.430(15) l.S03(1S) 1.425(15) 1.490(1S) 1.403(14) 1.502(16) 1.403(14) 1.492(16) 1.521(16) 1.547(12) 1.565(12) 1.563(12) 1.517(12) 1.533(13) 1.604(12) Distance( A) Mel -HlMl Mel -H2Ml Mel -H3Ml Me2 -HlM2 Me2 -H2M2 Me2 -H3M2 Me3 -HlM3 Me3 -H2M3 Me3 -H3M3 Me3 -H4M3 Me3 -H5M3 Me3 -H6M3 Me4 -HlM4 Me4 -H2M4 Me4 -H3M4 MeS -HlMS MeS -H2M5 Me5 -H3M5 MeS -H4M5 Me5 -H5M5 Me5 -H6M5 Me6 -HlM6 Me6 -H2M6 Me6 -H3M6 Me7 -HlM7 Me7 -H2M7 Me7 -H3M7 MeS -HlMS MeS -H2MS MeS -H3MS Me9 -HlM9 Me9 -H2M9 Me9 -H3M9 MelO -HlMl MelO -H2Ml MelO -H3Ml 0.959 0.946 0.943 0.94S 0.959 0.950 0 .944 0.944 0.954 0.951 0.940 0.951 0.956 0.941 0.9S3 0.9S5 0.939 0.959 0.962 0.943 0.94S 0.947 0.946 0.952 0.952 0.925 0.969 0.950 0.957 0.936 0.942 0.954 0.946 0.932 0.942 0.971 39 Table VIII. (Continued) Angle( 0 ) CpA -Ta -CpB F1 -Ta -F2 CpA -Ta -F1 CpA -Ta -F2 CpB -Ta -F1 CpB -Ta -F2 CpS -Cp1 -Cp2 Mel -Cp1 -Cp2 Mel -Cpl -CpS Cp3 -Cp2 -Cp1 Me2 -Cp2 -Cpl Me2 -Cp2 -Cp3 Cp4 -Cp3 -Cp2 Me3 -Cp3 -Cp2 Me3 -Cp3 -Cp4 CpS -Cp4 -Cp3 Me4 -Cp4 -Cpl Me4 -Cp4 -CpS Cp4 -CpS -Cpl MeS -CpS -Cpl MeS -CpS -Cp4 CplO -Cp6 -Cp7 Me6 -Cp6 -Cp7 Me6 -Cp6 -CplO Cp8 -Cp7 -Cp6 Me7 -Cp7 -Cp6 Me7 -Cp7 -CpS Cp9 -CpS -Cp7 Me8 -CpS -Cp7 Me8 -CpS -Cp9 Cp10 -Cp9 -CpS Me9 -Cp9 -Cp8 Me9 -Cp9 -Cp10 Cp9 -CplO -Cp6 MelO -CplO -Cp6 MelO -CplO -Cp9 F4 -P -F3 FS -F3 -P F6 -F3 -P F7 -F3 -P 140.1 100.3( 4) 102.2 103.6 102.5 102.2 107. 7(10) 12S.4(10) 126.8(10) 108.4(10) 128.1(11) 123.3(11) 106.6(10) 124.7(11) 128.0(11) 107.0(10) 123.S(l0) 126.9(10) 109.9(9) 122.8(10) 126.8(10) 106.9(9) 122.4(10) 129.4(10) 106.4(9) 12S.l(10) 128.2(10) 109.S(9) 12S.3(10) 12S.2(9) 108.2(9) 12S.3(9) 126.4(9) 109.0(9) 125.1(10) 124.0(9) 177.8(6) 91.l(6) 89.S(6) 89.2(6) Angle( 0 ) F8 -P -F3 FS -P -F4 F6 -P -F4 F7 -P -F4 F8 -P -F4 F6 -P -F5 F7 -P -F5 F8 -P -F5 F7 -P -F6 F8 -P -F6 F8 -·P -F7 H2Ml -Mel -HlMl H3Ml -Mel -HlMl H3Ml -Mel -H2Ml H2M2 -Me2 -HlM2 HlM2 -Me2 -HlM2 H3M2 -Me2 -H2M2 H2M3 -Me3 -H1M3 H3M3 -Mel -HlM3 H4M3 -Me3 -H1M3 HSM3 -Me3 -HlM3 H6M3 -Mel -HlMl H3Ml -Me3 -H2M3 H4Ml -Mel -H2M3 HSM3 -Me3 -H2M3 H6Ml -Mel -H2M3 H4Ml -Mel -H3M3 H5M3 -Me3 -H3M3 H6M3 -Mel -H3M3 HSMl -Me3 -H4M3 H6Ml -Me3 -H4M3 H6M3 -Me3 -H5M3 H2M4 -Me4 -HlM4 HlM4 -Me4 -HlM4 H3M4 -Me4 -H2M4 H2MS -MeS -HlMS HlMS -MeS -HlMS H4MS -MeS -H1MS HSMS -MeS -HlM5 H6MS -Me5 -HlMS 90.3(6) 90.9(6 ) 90.1 (6) 88.7(6) 90 .2(6 ) 88.2(6 ) 179.4(7) 89.1(6 ) 92.3( 7) 177.2(6) 90.S (6) 109.7 110.1 111.2 109.6 110.3 109.5 111.4 110.5 59.8 54.0 143.6 110.4 143.S 60 .2 53.6 53 .3 143.6 59.5 111.0 110.2 111.1 110.6 109.5 110.9 110.8 109.2 49.9 62.8 141.6 -tO Table VIII. (Continued) Angle( 0 ) H3M5 -Me5 -H2M5 H4M5 -Me5 -H2M5 H5M5 -Me5 -H2M5 H6M5 -Me5 -H2M5 H4M5 -Me5 -H3M5 H5M5 -Me5 -H3M5 H6M5 -Me5 -H3M5 H5M5 -Me5 -H4M5 H6M5 -Me5 -H4M5 H6M5 -Me5 -H5M5 H2M6 -Me6 -H1M6 H3M6 -Me6 -H1M6 H3M6 -Me6 -H2M6 H2M7 -Me7 -HlM7 H3M7 -Me7 - H1M7 H3M7 -Me7 -H2M7 H2M8 -Me8 -H1M8 H3M8 - Me8 -H1M8 H3M8 -Me8 -H2M8 H2M9 -Me9 -HlM9 H3M9 -Me9 -HlM9 H3M9 -Me9 -H2M9 H2Ml -MelO -HlMl H3Ml -MelO -HlMl H3Ml -MelO -H2Ml 110.5 141.9 50.9 63 .2 62.0 142.1 50.1 109.9 109.4 111.2 111.0 110.3 110.6 112.2 108.5 110.8 109.6 111.3 110.8 110.7 111.3 110.4 112.6 110.0 109.2 41 Table IX. Assigned Hydrogen Atom Parameters for [Cp""2TaF2HPF6l (20 ). :z:,y and z x 10 4 Atom H1M1 H2M1 H3M1 H1M2 H2M2 H3M2 H1M3 H2M3 H3M3 H4M3 H5M3 H6M3 H1M4 H2M4 H3M4 H1M5 H2M5 H3M5 H4M5 H5M5 H6M5 H1M6 H2M6 H3M6 H1M7 H2M7 H3M7 H1M8 H2M8 H3M8 H1M9 H2M9 H3M9 H1M10 H2M10 H3M10 :z: y z B 6558 5479 5466 8897 7857 8232 9168 8272 8398 8927 8857 8054 6821 5635 5808 4864 4554 4210 4575 4853 4200 6419 5720 6383 7360 6563 6356 10210 9649 9041 10922 10481 10868 9039 7968 9180 4476 5006 3791 5357 6113 5267 4280 4173 5252 4995 3889 4820 2926 2568 3742 2129 2901 3193 2511 2343 3368 -190 803 839 -351 651 -221 633 1700 614 1393 2568 1969 1014 1766 2236 3358 3769 3549 4822 4633 3960 6222 6954 6468 6151 6604 6890 7150 6773 7081 5230 4485 5414 5585 4625 4919 6039 5730 6596 3801 3757 4449 3852 3548 3356 5790 5731 4910 7120 7166 6958 6.8 6.8 6.8 9.4 9.4 9.4 9.2 9.2 9.2 9.2 9.2 9.2 8.0 8.0 8.0 7.8 7.8 7.8 7.8 7.8 7.8 8.1 8.1 8.1 8.3 8.3 8.3 7.0 7.0 7.0 6.1 6.7 6.7 7.3 7.3 7.3 42 Chapter 3 [2+2] Cycloaddition, Insertion, and Substitution Reactions of Tantalum Imido and Amido Complexes ABSTRACT ................................................................................. 43 INTRODUCTION .......... ............................ ................................. 44 RESULTS AND DISCUSSION ............ .... ........ .... .... ......... ....... 54 CONCLUSION ............................................................................ 63 EXPERIMENTAL ... .. .. .. . .. .. .. . .. .. ..... ...... .. .. ...... .. .. .. ... .. ...... .. .. ... .. . .. . 64 REFERENCES ... .. .. .. ... .. .. . .. .. ... .. ... .. .. . .. .. ... .. ... .. .. ... .. .. .......... .. .. ... . .. . 71 APPENDIX II ............................................ .... ......... .. .. .. ................ 75 43 The synthesis of reactive tantalum imido and amido complexes is described. Treatment of Cp*TaC4 with four equivalents of lithium anilide affords Cp*Ta(=NPh)(NHPh)2. This complex reacts readily with substituted anilines to generate Cp*Ta(=NPh')(NHPh'h and with alcohols such as pinacol to afford Cp*Ta(OCMe2CMe20h, products whereby both the imido and amido groups are exchanged. Exposing Cp*Ta(=NPh)(NHPhh to C02 resulted in the isolation of Cp*Ta(OCONPh)(T)2-0CONHPhh with both the formal [2+2] addition of C02 across the imido group and insertion of C02 into the amido group. Finally, bis-irnido complexes were prepared by exposing Cp*Ta(=NPh)(NHPhh to one equivalent of HCl to afford Cp*Ta(=NPhh or by treating Cp*TaCl4 with four equivalents of lithium 2,6-diisopropylanilide to yield Cp*Ta(=NPh"h with Ph" = 2,6-diisopropylphenyl. Abstract: 44 Introduction Since the first report of a transition metal imido complex forty years ago,l the number of complexes with this functional group has dramatically increased. The preparation of such complexes has been actively pursued because of the unique properties this ligand imparts to metal complexes. The imido group can act as a two or four electron donor and the metal valency can be deduced by the position of the substituent on the nitrogen.2 LM=N n •• / R n As a four electron donor with an sp hybridized nitrogen atom, the M-N-R bond angle is expected to be 180°. For a two electron donor with a pair of electrons in a nitrogen sp2 orbital, the M-N-R bond angle is expected to be 120°. All but one crystallographically characterized structures of terminal imido complexes have bond angles greater than 155°, suggesting that nearly all imido groups have triple-bond character. The imido moiety has been of major interest due to its potential in catalytic processes) For example, metalimido groups are important catalysts in the preparation of aziridines and amines.4 The great advantage of the imido group is the ability to control both the electronic and steric effects of the ligand. By using electron-donating or electron-withdrawing groups, the degree of rr bonding and the strength of the rr bond can be modulated. Furthermore, the steric bulk of the substituent on the nitrogen can also be used to adjust reactivity. For instance, bulky imido groups prevent dimerization reactions that lead to imido-bridged complexes. As one example, the Schrock alkylidene-imido complex (1) with the 2,6diisopropylphenyl imido group are stable, highly reactive catalysts for olefin metathesis .5 45 M ~y RO', .. M- / RO 1 However, a change to a 2,6-dimethylphenylimido group results in decomposition of the complex; presumably, there are bimolecular decomposition pathways available with the less sterically bulky group. Recently, several early transition metal complexes have been prepared which contain reactive imido groups. Wolczanski6 ,7 has generated a series of coordinative unsaturated transition metal complexes with bulky silylamide ligands. It was shown that the thermolysis of the alkyl complex 2 led to C-H activation, presumably through the transient 14 electron imido complex 3.8 In benzene, 2a produced 4 by the activation of the benzene C-H bond with concomitant loss of methane. Scheme I tBu 3SiNH "' tBu3SiNH-Zr -R tBu3SiNH / 2a, R = CH 3 b, R =Ph c, R = Cy 4 3 tBu 3SiND"' tBu3SiND-Zr -C6 Ds tBu3SiND/ 5 6 The intermediacy of a 14 electron bis(amido)imido complex 3 was confirmed when (tBu3SiNH)3ZrCH3 was thermolyzed in C6D6: 46 (tBu3SiND)(tBu3SiNH)2ZrC6Ds and (tBu3SiND)2(tBu3SiNH)2ZrC6Ds appeared and then reacted further to afford 5. Finally, methane activation was demonstrated by the thermolysis of (tBu3SiNH)3ZrCD3 with CH4. Complex 2a was the sole organometallic species isolated and CD3H was observed spectroscopically. The isolable titanium analog,9 (tBu3SiNH)2Ti(=NSitBu3)(Et20), has also been found to undergo C-H activation of benzene. However, the related five-coordinate (Ar'0)2Ti(=NPh)(py'h where Ar' = 2,6-diisopropylphenyl and py' = 4-pyrrolidinopyridine does not react with benzene or methane.lO Presumably, with the weaker rr-donation of the alkoxyl groups relative to the amido groups, the compound coordinates two nitrogen donors, leading to an unreactive complex. Bergman11 has provided evidence for the presence of the 16 electron [Cp2Zr=NR] (8) as a transient species from the thermolysis of Cp2Zr(NHR)CH3 (7). Scheme II /NHR ~ Cp2Zr"--C....::H:......_4CH3 7a, R = p-C6H 4-tBu b, R = tBu 8 9 C, R = 2,6-C6H 3(CH3)2 R I N Cp,ZrYR" R' lOa, b, c 11, R' = Me, R" = Ph 12, R' = Ph, R" = Ph 13, R' = Me, R" =Me The intermediate imido species 8 is capable of C-H activation of benzene, and the highly electrophilic nature of the metal center is shown by its coordination with donor ligands such as THF, as shown in the crystallographically characterized complex lOb. Though lOb contains a linear Zr-N-C linkage which suggests that the imido group is acting as a 4 electron 47 donor, it does not necessarily follow that Cp2Zr(=NR)THF is a 20 electron complex.12 Finally, thermolysis of the zirconium amido alkyls in the presence of alkynes results in the formation of azametallacyclobutenes (11, 12, 13). Exposure of these complexes to wet silica gel generates enamines that are hydrolyzed to ketones. A low valent late transition metal complex that contains a terminal imido group is rare.13 However, Cp*Ir=NtBu (15)14 has been prepared and the crystal structure reveals a Ir-N bond distance of 1.71A, which is typical of Ir-N triple bonds and the Ir-N-C linkage is nearly linear (bond angle of 1770). Furthermore, the imido complex does not coordinate acetonitrile or triphenylphosphine. These results indicate that 15 is an 18 electron complex; though it readily undergoes [2+2] cycloaddition reactions with carbon dioxide and isocyanides to form metallacycles such as 16. >9< [(TJs-CsMes)IrClzlz LiNHtBu Ir 0 14 1\. y N-tBu 0 15 16 Recently, a vanadium bisimido complex15 has been proposed as an intermediate in the C-H activation of methane and benzene. The precursor alkyl complexes (18) are formed by treating V(=NSitBu3)(NHSitBu3)Cl with an alkyllithium reagent. tBu 3SiN tBu3SiN \\ tBu3SiHN ''jV -Cl tBu3SiHN 17 LiR' \\ ..V-R' tBu3SiHN''f tBu 3SiHN 18a, R' =Me b, R' = nBu c, R' = CH 2CMe3 d, R' = CH 2SiMe 3 48 Subsequent thermolysis of 18a in the presence of 13CH4 resulted in the isotopically-labeled product 20. The formation of CH4, instead of CH3D, when 18a was heated in C6D6 indicates that the reaction does not proceed by a cr bond metathesis mechanism.16 These results suggest that the 16 electron bis(imido)amido complex, (RNH)V(=NRh, is an intermediate in these reactions. Scheme III tBu 3SiN tBu3SiN \\ \\ .. V-CH 3 ..v-c6Hs tBu3SiHN''/ tBu3SiHN 13 CH 4 tBu3SiHN''/ tBu 3SiHN 19 18a 20 21 This intermediate can be trapped by diethyl ether, THF, or pyridine to form 21 . The steric influence of the tert-butylsilyl groups is demonstrated by C-H activation exclusively at the methyl groups of mesitylene to afford 22. Cyclopentadienyl complexes with imido groups have also been examined. Wigleyl7 has synthesized a tungsten bisimido complex 24 that undergoes intramolecular C-H activation to form the "tuck-in" complex 26 (Scheme IV). 49 Scheme IV LiCp* 24 23 LiNH=P >95- ~~w:p 25a, R =Me b, R =Ph 26 The conversion of 24 to 26 presumably proceeds via the intermediate shown in Scheme V. Interesting, under the reaction conditions employed for the preparation of 25, 26 is not observed even though loss of alkane is known to be facile. 50 Scheme V LiNHAr' / 24 ~ I w..........._ .. Ar'-N 1/ N A(. 26 Ar' = N .... ,H \ Ar' Complex 24 has been structurally characterized and contains linear phenylimido linkages (W-N-Cipso = 1680 and 171 O). One of the W-Cp* ring carbon distances is short (2.33 A) while the other four W-Cp* carbon distances are greater than 2.43 A. Furthermore, the ring exhibits some electron localization to a 1,4-diene unit. This effect can be ascribed to a trans influence of the imido groups, resulting in a weakening of the double bond components of the 115-CsMes ring.18 Schrock19 has recently proposed that the 6 electron dianionic imido group is analogous to the 6 electron cyclopentadienide ligand. This line of reasoning leads to the question of whether the cyclopentadienyl group can be replaced by an imido group and what the effect of such a replacement would be on the reactivity of transition metal complexes.20 Recently, several tungsten (IV) bisirnido complexes were prepared, including W(=NArh(PMe2Phh (27) where Ar = 2,6-CJ-!3-1Pr2. 51 27 The four coordinate d2 complex is pseudotetrahedral with linear imido groups and two metal-nitrogen rr bonds for each imido moiety. With the 1 a and 2 rr interaction between the metal and each of the imido moieties, the W(=NArh is a 14 electron fragment and is both isolobal and isoelectronic with the Cp2Hf fragment. Recently, Gibson21 has carried out Fenske Hall calculations on the complex CpNb(=NMe)Cl2 in order to compare it with the group 4 metallocenes, Cp2MCl2. Both the Cp and imido ligands are 1 a, 2 rr donors with the a orbital of a1 symmetry and the rr orbitals of e1 symmetry. The metallocene system has been previously studied by Hoffmann.22 The Cp2M fragment contains 1a1, b2, and 2a1 symmetric frontier orbitals that contribute to the binding of ligands to the metal center. -¥ 2a 1 ~ )-x y -¥ R/ M ~ N b2 .. ~ IX z z 1a1 * Figure 1. Frontier molecular orbitals for a bent metallocene and [Cp*M(=NR)] fragment. 52 When comparing the results from the Fenske Hall calculations for CpNb(=NMe)Cl2 and Cp2MCl2, the frontier orbitals are similar in their molecular orbital compositions. The only significant difference lies in the 2a, orbital of the imido complex, which exhibits a substantial amount of dxz character. Table I. Fenske Hall Frontier Orbital Contributions for [Cp2Zr] fragment Orbital % Contribution Ligands Metal 1a1 11 84 dv2, 5 S h2 27 66 dyz, 7py 2a, 14 36 d 2 2-x2, 33 S, 17 Pz Table II. Fenske Hall Frontier Orbital Contributions for CpNb(=NR) fragment Orbital % Contribution Ligands Metal 1a, 12 79 dy2, 9 s h2 41 2a1 24 57 dvz, 2 dxv 23 d 2 2.._x2, 19 dxz, 18s, 14 Pz, 2 Px The resultant orbital is directed out of the normal wedge of the bent metallocene and could result in differences in the reaction chemistry of metallocene and half-sandwich imido complexes. The reactive imido complexes discussed in this introduction are electrophilic (12 to 16 electron metal centers) and many contain bulky ancillary ligands (tert-butylsilyl and 2,6-diisopropylphenyl) in order to prevent dimerization. Furthermore, the coordinative unsaturation of the metal plays a role in the reactivity of these complexes.23 As mentioned in the introduction to chapter two, the goal was the preparation of "rr-loaded" 53 complexes in which an oxo or imido group would not be maximally bonded to the metal center. Therefore, this chapter will describe the preparation and reaction chemistry of several complexes which contain the [Cp*Ta(=NR)] fragment. Specifically, the synthesis and reaction chemistry of Cp*Ta(=NPh)(NHPhh will be described, which contains both reactive imido and amido groups. Furthermore, the preparation of two bis-imido complexes will be presented. 54 Results and Discussion The preparation of reactive tantalum imido complexes was attempted by treating readily available Cp*TaCl424 with trimethylsilyl amines and lithium amides or anilides. If a mono-imido complex (28) can be prepared, introduction of a second oxo, imido, or alkylidene group should be facile. (Scheme VI) Scheme VI Cp*TaC1 4 2TMSNHR or 2LiNHR 28 R =alkyl or aromatic group X= 0 , NR, CR2 29 When Cp*TaC4 was treated with two equivalents of trimethylsilyltert-butylamine, Cp*Ta(NHtBu)Cl} (30) was isolated as the only product. Cp*TaCl 4 + 2tBuNHTMS - - - - - 800C I 3 days CH 2Cl 2 30 55 Similarly, when PhNHTMS was used, Cp*Ta(NHPh)Cb (31) was formed as the exclusive product. Recently, it has been reported that heating the reaction mixture at sooc for 10 days affords the imido complexes, Cp*Ta(=NR)Cl2.25 However, subsequent attempts to deprotonate Cp*Ta(NHtBu)Cl3 or Cp*Ta(NHPh)Cl3 to generate imido complexes were unsuccessful. Complexes with imido and amido functionalities were produced when lithium amides and anilides were employed. The complex Cp*Ta(=NPh)(NHPhh (32) was prepared by treating Cp*TaCl4 with four equivalents of lithium anilide in THF. A yellow product was isolated in good yield. T_H_F_ _ Cp*TaC1 4 + 4LiNHPh _ _ ~ ... NHPh O ~, NHPh N ; 32 Complex 32 exhibited a singlet at 5.90 ppm for the equivalent amido protons. The Be NMR spectrum contains the appropriate number of peaks for one imido and equivalent amido groups. As is the case with Mo(=NAr')z(NHAr')z (Ar' = 2, 6-diisopropylphenyl)26, variable temperature NMR studies showed that proton transfer does not occur between an amido and imido group on the NMR time scale. The structure of 32 was determined by an X-ray diffraction study and an ORTEP drawing is shown in Figure 2. The Ta-N bond distance of 1.78A for the imido group is typical for a triply bonded imido group (compare to (Me2NhTa(NtBu) with 1.77A and (PEt3)Cl(THF)zTa(NPh) with 1.77A) .27,28 However, unlike the bis-imido complexes described in the introduction, the sole imido group of 32 does not exert a trans influence sufficient to effect a slippage of the Cp* ring to 11 1,11 4 - or 112,113_ coordination. The tantalum-Cp* ring carbon distances are within O.lA of each other, and no electron localization is evidenced by the Cp* carbon distances either. 56 Figure 2. ORTEP diagram of Cp"'Ta(=NPh)(NHPhh (32). 57 Table III. Selected distances (A) and bond angles (deg) for Cp*Ta(=NPh)(NHPhh (32) Ta-Cp* Ta-N1 Ta-N2 Ta-N3 N1-C1 2.126 (3) 1.784 (5) 2.013 (5) 2.029 (5) 1.383 (6) Distances N2-C11 N3-C21 N2-HN2 N3-HN3 1.395 (6) 1.395 (6) 0.974 0.972 Bond Angles N1-Ta-Cp* 120.2 (2) N2-Ta-N3 106.0 (2) Ta-N1-C1 166.7 (4) Ta-N2-C11 Ta-N3-C21 134.4 (3) 132.9 (3) Initial attempts to expel a second equivalent of aniline to produce Cp*Ta(=NPhh were not successful. Thermolysis and the addition of donor compounds such as PMe3 resulted in the observation of 32 with small amounts of decomposition. Also, neither C-H activation chemistry of benzene nor cycloaddition of ethylene or 2-butyne were observed. However, Cp*Ta(=NPh)(NHPhh does react with alcohols, amines, and water. Treatment of 32 with H20 generates a complex (34) which had been previously prepared by another route.29 Alcohols such as pinacol react with 32 to afford a product (33) in which both the imido and amido groups are replaced.30 Finally, treating 32 with PCls and AlCl3 results in the isolation of Cp*TaCl431 (Scheme VII). 58 Scheme VII ~ ..,NHPh a 2 eq. pinacol ~' NHPh # 32 33 A1Cl 3 or PC15 Cp* I o-Ta-o HO" I 1\\ \ /OH Ta-O 0 0-Ta Cp*/ \ \ / / / "cp* * Cl"' ......Ta -.....,,Cl Cl / " Cl 0-Ta--o I Cp* 34 Amines afford new imido-amido complexes. Treating 32 with 20 equivalents of NH2Ph' (Ph' = p -NH2C6HtX, X= CH3, OCH3, N02, F) affords Cp*Ta(=NPh')(NHPh'h. With mono-, di- and tri- substituted products in the reaction mixture, the rates of the imido / amido transformation were difficult to quantitate. In addition, a large excess of the substituted anilines was necessary to drive the reaction to completion. However, the relative rates of the reactions suggest a mechanism for the imido-amido exchange in which there is a rate-determining pre-coordination of the amine prior to proton transfer. With electron-donating groups at the para position of the substituted aniline, the exchange was quite facile at room temperature. With an electron-withdrawing group at the para position, heating the reaction was necessary in order to drive the reaction to completion. These results are in agreement with the mechanisms shown in Schemes VIII and IX, which result in the exchange of both imido and amido groups.32 59 Scheme VIII ~NHPh+NHR ~' ON NHPh dNH ~a.:NHR 2 ON Ph ~'NHPh 2 ~NHR O +NHPh ~ ' NHPh N 2 ~ Scheme IX ~NHPh ~NHPh ON 0 ~, NHPh >9< PhNH·"··Ta .....,NHPh RNH/ 'NHPh N~~ 'NHPh - - - - - - ~H2 R ~NHPh ~' R NHPh + NHPh 2 These results lead to the intriguing conclusion that coordination of the amine to what might be an eighteen electron metal center is required prior to proton transfer. The crystal structure and the lH NMR spectrum indicate that 32 contains equivalent amido groups. These exchange reactions indicate, however, that 32 can exist as a sixteen electron complex, therefore, without a dative bond from one of the amido groups. Once coordinated, the amine would be expected to undergo facile proton transfer, for the intermediate would contain a partial positive charge on the nitrogen and acidic protons. In order to simplify the 1 H NMR spectra for the imido-amido exchange reaction with amines, Cp*Ta(=N-p-C6H4Me)(NH-p-C6H4Me)2 was prepared. 60 Treatment of Cp*TaCl4 with 4 equivalents of para-toluidine gave 35 in high yield. Further studies with 35 to determine reaction rates with amines have not been attained. Cp*TaC1 + 4LiNHPh' _ _ T_H_F_ _ 4 ~ 0-, ... NHPh' r\N NHPh' )-/ 35 When 32 was treated with excess C02, both [2+2] addition of carbon dioxide across the imido group and insertion into the amido group affords 36.33 Complex 36 contains two 112-carbamate groups from C02 insertion and the metallacycle from the formal [2+2] addition of a C=O bond of C02 with a tantalum imido bond.34 The hapticity of the carbamates was confirmed by a X-ray structure analysis with the ORTEP drawing shown in Figure 3. ~ a .. NHPh C02 (excess) # 'NHPh # 32 36 Interestingly, at room temperature, the lH NMR spectrum of 36 in THF-ds showed a broad singlet for the N-H resonances while the 13C NMR spectrum exhibited four resonances in the carbonyl region. Cooling the sample resulted in more complex spectra. These observations can be attributed to a fluxional process involving either (1) a change in the hapticity of the carbamates or (2) C-N bond rotation of the carbamate groups or (3) a proton transfer from the 112-carbamate to the O,N-metallacycle with rearrangements of both. 61 C21 C14 Figure 3. ORTEP diagram of Cp"'Ta(OCONPh)(ll2-0CONHPhh (36) 62 However, the rearrangements are probably assisted by THF. The complex was found to be insoluble in benzene, toluene and methylene chloride. The solid state infrared spectrum of 36 exhibited two peaks at 1571 and 1603 cm-1 which are characteristic of T)2-carbamates and two peaks at 1699 and 1655 cm-1 for the carbonyl group of the O,N-cyclometallacarbamate.35,36 The preparation of a bis-imido complex was attempted next. Neither thermolysis of 32 nor the addition of donor ligands such as THF and PMe3 to 32 resulted in the loss of an equivalent of aniline. However, treatment of 32 with HCl resulted in the isolation of Cp''Ta(=NPhh (37) with the concomitant formation of [NH3Ph]Cl. ~ O ... NHPh ~, N # 32 NHPh HCl ,1f,:N-o 0 N 37 This complex is isostructural and isoelectronic to [Cp2Zr=NtBu]. However, 37 was found to be unreactive toward benzene when heated to 80°C. Further heating to 120°C only resulted in its decomposition. A solution molecular weight determination of 37 in benzene indicates that it is monomeric in solution. The infrared spectrum could be helpful since bridging imido stretches tend to be 50-100 cm-1 lower in energy than their terminal imido counterparts.37 However, since the Ta-N and C-N stretches are coupled in 37, it is difficult to access the infrared data here. Finally, the crystal structure of Cp*Ta(=NPh')Cl2 where Ph' = 2,6diisopropylphenyl suggested that the steric environment of the diisopropylphenyl group would not preclude reaction of Cp*TaCl4 with the lithium anilide to generate Cp*Ta(=NPh')Cl2. However, a complex isostructural to 32 would not be expected. This means that the loss of a second equivalent of 2,6-diisopropylaniline to form Cp*Ta(=NPh'h is expected. When Cp*TaC4 was treated with four equivalents of lithium 2,6diisopropylanilide, a yellow solid was isolated (38).38 63 Cp*TaC1 4 + 4LiNHPh' _ _ T__H___F_____. Ph' = 38 Conclusion A series of tantalum imido complexes have been synthesized and contain both reactive imido and amido functional groups. Cp*Ta(=NPh)(NHPh)z (32), which is prepared from Cp*TaCl4 and lithium anilide, contains imido and amido ligands that react with alcohols, amines, and water, resulting in the isolation of several novel tantalum species. Also, 32 was found to both insert C02 at the amido groups and undergo a cycloaddition at the imido group to form the crystallographically characterized Cp*Ta(OCONPh)(T)2-0CONHPhh (36). Finally, bis-imido complexes such as Cp*Ta(=NPh)z (prepared by treating 32 with hydrochloric acid) or Cp*Ta(=NPh'h where Ph' = 2,6-diisopropylphenyl (treating Cp*TaCl4 with lithium 2,6-diisopropylanilide) have not been a particularly reactive species. 64 Experimental General Considerations. All manipulations were performed using glovebox or high vacuum line techniques.39 Solvents were dried over LiAlH4 or Na/benzophenone and stored under vacuum over "titanocene."40 Benzene-d6 and tetrahydrofuran-ds, were dried over activated molecular sieves (4A, Linde) and stored over "titanocene" or Na/benzophenone. Argon and nitrogen gases were passed over MnO on vermiculite and activated sieves. Many reactions were monitored by NMR spectroscopy. Any experiment described in this chapter but not explicitly listed below was carried out in a sealed NMR tube using -0.7 mL of the NMR solvent with the appropriate reagents. Cp*Ta(NHtBu)Ch (30). A high pressure reaction vessel was charged with 1.53 g (3.34 mmol) Cp*TaCl4. On the vacuum line, 50 mL methylene chloride was condensed on the solid at -78°C. Tert-butyltrimethylsilylamine (1.50 mL, 1.13 g, 7.77 mmol) was added via syringe into the vessel under positive Ar flow. The reaction vessel with the homogeneous solution was heated at 80°C for 30 hours. The resultant solution and precipitate was transferred to a swivel frit assembly. Filtration affords 701 mg (1.42 mmol) of an orange solid. Yield = 43%. Analysis: Calculated (Found) C: 33.99 (34.99); H: 5.09 (5.38); N : 2.83 (2.75). Cp*Ta(NHPh)Ch (31). Approximately 50 mL methylene chloride was condensed into a high pressure reaction vessel containing 9.88 g (21.6 mmol) Cp*TaCk This solution was transferred to a dry box where 7.17 g (43.3 mmol) phenyltrimethylsilylamine was added. This reaction mixture was then heated at 70°C for 2 weeks. The resultant orange-red solution was transferred to a swivel frit assembly. Filtration affords an orange solid (4.28 g, 8.32 mmol) which was then washed with methylene chloride. Yield = 39%. Analysis : Calculated (Found) C: 37.34 (34.56); H : 4.11 (3.86); N : 2.72 (2.71). Cp*Ta(=NPh)(NHPh)2 (32). A 100 mL round bottom flask was charged with 8.05 g (17.6 mmol) Cp*TaC4 and 6.97 g (70.4 mmol) lithium anilide. The flask was attached to a swivel frit assembly. Approximately 70 mL THF was condensed on the solids at -780C and the solution was allowed to warm slowly to room temperature. The red solution was then stirred for another 20 65 hours. After removing the volatiles in vacuo, toluene was condensed on the solid and the lithium chloride was filtered. The toluene was then removed in vacuo and diethyl ether was condensed into the flask. Filtration affords 3.86 g (6.53 mmol) of a bright yellow solid. Yield = 37%. IR spectroscopy (nujol mull, cm-1 ): 1558.9, 1592.8, 1347.2, 1249.1. Analysis : Calculated (Found) C: 56.85 (56.17); H : 5.45 (5.37); N : 7.10 (6.69). Cp"'Ta(OCMe2CMe20h (33). A 100 mL round bottom flask was charged with 3.11 g (5.26 mmol) Cp"'Ta(=NPh)(NHPhh and 1.23 g (10.4 mmol) pinacol. A swivel frit assembly was attached. Approximately 35 mL toluene was then condensed on the solids at -78°C. The resultant solution was stirred at -780C for one hour at which the dry ice/acetone bath was removed and the volatiles were removed in vacuo. Then approximately 20 mL petroleum ether was added and a yellow solid (1.97 g, 3.59 mmol) was filtered. Yield= 68%. Analysis : Calculated (Found) C : 48.17 (48.13); H: 7.17 (6.94). Cp"'Ta(OCONPh)(ll2-0CONHPh)2 (36). A high pressure reaction vessel was charged with 705 mg (1.19 mmol) Cp"'Ta(=NPh)(NHPhh. Approximately 20 mL toluene was condensed on the solid at -78°C. Then approximately 3 equivalents of carbon dioxide was added at -1960C using a gas bulb. The resultant solution was allowed to warm to room temperature. The reaction vessel was placed on a device to shake the solution. Within the hour, the solution appeared orange and after 3 hours, an insoluble solid had appeared. After 22 hours, one atrnospherere of carbon dioxide was introduced. After 48 hours, the solution and precipitate was transferred to a swivel frit assembly. Filtration affords a white product (408 g, 0.56 rnrnol) and washed with toluene and then petroleum ether. Yield= 47%. IR spectroscopy (KBr, cm-1): 3292.2, 3057.8, 2913.7, 1699.2, 1654.5, 1603.5, 1570.9, 1500.3, 1490.0, 1438.7, 1326.1. Analysis : Calculated (Found) C: 51.46 (50.65); H : 4.46 (4.59); N : 5.81 (5.27). Cp"'Ta(=NPhh (37). A 50 mL round bottom flask was charged with 770 mg (1.30 mmol) Cp"'Ta(=NPh)(NHPhh. A swivel frit assembly was attached. Approximately 25 mL benzene was then condensed into the reaction vessel at -78°C followed by 1 equivalent of HCl from a lecture bottle using a gas bulb. The resulting solution was stirred for 3 days at room temperature. Then the volatiles were removed in vacuo, leaving a yellow solid. The product was 66 washed with petroleum ether and toluene to afford 150 mg (0.32 mmol ) of 37. Yield = 25%. IR spectroscopy (nujol mull, cm-1 ): 1463.2, 1348.9, 1248.3. Analysis: Calculated (Found): C: 53.02 (48.01); H : 5.06 (4.65); N : 5.62 (4.90). Cp*Ta(=NPh'b (Ph' = 2,6-diisopropylphenyl) (38). A 100 mL round bottom flask was charged with 3.00 g (6.55 mmol) Cp*TaC4 and 4.80 g (26.20 mmol) lithium 2,6-diisopropylanilide. A swivel frit assembly was attached. Approximately 50 mL THF was then condensed on the solids at -78°C at which the solution turned blue-green immediately. The resultant solution was then stirred at room temperature for 2 days. The volatiles were removed in vacuo. Petroleum ether was condensed onto the solids and the LiCl was filtered . Concentration and cooling the brown solution affords a yellow solid (714 mg, 1.07 mmol). Yield= 16%. IR spectroscopy (KBr, cm-1 ): 2952.9, 2920.6, 1460.7, 1434.0, 1380.2, 1359.9, 1339.11, 1289.2, 1260.9, 1245.6, 1191.5, 933.4, 857.8, 799.0, 755.4. Analysis: Calculated (Found) C: 61.25 (61.14); H : 7.41 (7.70); N: 4.20 (3.81). X-Ray Crystal Structure Determination of Cp*Ta(=NPh)(NHPh)2. The ORTEP drawing of Cp*Ta(=NPh)(NHPhh is shown in figure 2 with important bond angles and distances in Table III. To obtain the structure, a yellow crystal was mounted in a greased capillary. The crystal was then centered on a CAD-4 diffractometer. Unit cell parameters and an orientation matrix were obtained by a least squares calculation from the setting angles of 25 reflections with 150 < e < 17°. The data were corrected for absorption. Coordinates of the tantalum atom were obtained from a Patterson map; locations of the other non-hydrogen atoms were determined from successive structure factor-Fourier calculations. Calculations were done with programs of the CRYM Crystallographic Computing System and ORTEP with scattering factors and corrections for anamalous scattering taken from a standard reference.41 67 X-Ray Crystal Structure Determination of Cp''Ta(OCONPh)(Tl2-0CONHPhh. The ORTEP drawing of Cp*Ta(OCONPh)[OC(=O)NHPhh is shown in figure 3. To obtain the structure, a colorless crystal, obtained from cooling a THF I pentane solution, was oil-mounted on a glass fiber and transferred to the Synthex P21 diffractometer. The intensity data was collected at 163 K and corrected for absorption. The structure was solved by direct methods (SHELXTL) and refined by full-matrix least square techniques. 68 Table IV. 1H NMR Spectral Data for compJ exes 30 - 38 Compound Assignment 8 (ppm) Cp*Ta(NHtBu)Cl3 (30) NH-C(CH3)} 1.51 (s) 2.59 (s) in CD2Cl2 Cp*Ta(NHPh)Cl3 (31) in C6D6 Cs(CH3)5 N-H 4.40 (s, br) para-C6Hs 2.26 (s) 6.17 (s, br) 6.82 (t) 7.20 meta-C6Hs 6.98 (t) 8.10 ortho-C6Hs 7.23 (d) 7.80 Cs(CH3)5 N-H Cp*Ta(=NPh)(NHPhh 1.72 (s) (32) in C6D6 5.90 (s) Cp''Ta(OCMe2CMe20h (33) in C6D6 J (Hz) aromatic 6.8-7.5 O-C-CH3 O-C-CH3 1.27 (s) 1.48 (s) Cs(CH3)5 2.06 (s) Cs(CH3)5 2.16(s) Cp*Ta(NPhOCOh (OCONHPhh (36) N(imido)-p-C~s 6.51 (m, br) in THF-ds N(imido)-m-C~s 6.81 (t, br) N(amido)-p-C~s 6.99 (t) 7.23 (t) 7.50 8.40 7.50 N(imido)-o-C~s 7.33 (d) 7.52 (d) N-H 9.41 (s) Cs(CH3)5 aromatic 1.79 (s) N(amido)-m-C~s N(amido)-o-C~s Cp*Ta(=NPhh (37) in C6D6 Cp*Ta(=NPh'h (38) in C6D6 9.60 6.74-7.26 N-CH-(CH3)2 N-CH-(CH3)2 1.21 (d) 6.90 1.28 (d) 6.90 N-CH-(CH3)2 N-CH-(CH3)2 1.34 (d) 1.40 (d) 6.60 6.60 Cs(CH3)5 1.91 (s) N-CH-(CH3h N-CH-(CH3h 3.56 (br) aromatic 6.8-7.2 4.01 (br) 69 T a ble V 13C NMR S'pee tr a1 D ata f or comp. exes 30 - 38 Compound Cp*Ta(NHtBu)Cl3 (30) in CD2Cl2 Cp*Ta(NHPh)Cl3 (31) in CD2Cl2 Assignment 8 (ppm) Cs(CH3)5 NH-C(CH3)3 13.54 30.71 NH-C(CH3)3 56.91 Cs(CH3)5 133.76 Cs(CH3)5 aromatic 13.56 122.72 aromatic 125.82 aromatic 128.55 133.53 Cs(CH3)5 aromatic Cp*Ta(=NPh)(NHPhh (32) in C6D6 Cs(CH3)5 aromatic aromatic aromatic Cp*Ta(OCMe2CMe20h (33) in C6D6 Cp*Ta(NPhOC0)2 (OCONHPh)2 (36) in THF-d s 141.74 10.52 116.26 119.42 aromatic 119.79 122.75 aromatic 126.52 aromatic aromatic aromatic 127.85 aromatic 153.23 Cs(CH3)5 O-C-CH3 11.91 27.11 O-C-CH3 29.17 O-C-CH3 95.44 Cs(CH3)5 121.28 Cs(CH3)5 aromatic aromatic 10.06 119.94 aromatic 121.69 aromatic aromatic 124.31 124.94 aromatic aromatic 127.96 129.67 128.45 129.20 120.32 70 T abl e V (C ontmue d) 13C NMR spectra Cp*Ta(=NPhh (37) in C6D6 aromatic 138.00 aromatic 153.20 aromatic 160.59 aromatic aromatic aromatic 161.48 162.96 165.70 Cs(CH3)5 aromatic 10.79 Cs(CH3)5 aromatic aromatic 120.52 aromatic 126.28 aromatic 129.02 152.06 aromatic Cp*Ta(=NPh'h (38) in C606 118.08 Cs(CH3)5 N-CH-(CH3h 122.20 123.33 10.92 N-CH-(CH3h 22.55 23,73 N-CH-(CH3h 24.42 N-CH-(CH3h N-CH-(CH3h N-CH-(CH3h 25.56 27.51 28.33 118.19 Cs(CH3)5 aromatic 122.33 aromatic 123.56 aromatic 123.89 aromatic 125.03 142.03 aromatic aromatic 145.01 71 References 1. Clifford, A. F.; Kobayashi, C. S. Abstracts of the 130th National Meeting of the American Chemical Society, Atlantic City, New Jersey, September, 1956, p. 50R. 2. (a) Nugent, W. A.; Haymore, B. L. Coord. Chern. Rev. 1980, 31, 123. (b) Nugent, W. A.; Mayer, J. M. Metal-Ligand Multiple Bonds, John Wiley and Sons, New York, 1988. 3. See chapter 1. 4. The lone exception is Mo(NPh)2(S2CNEt2h from Haymore, B. L.; Maata, E. A.; Wentworth, R. A. D. f. Am. Chern. Soc. 1979, 101, 2063. 5. (a) Schrock, R. R.; DePue, R. T.; Feldman, J.; Yap, K. B.; Yang, D. C.; Davis, W . M.; Park, L.; Dimare, M.; Schofield, M .; Anhaus, J.; Walborsky, E.; Evitt, E.; Kruger, C.; Betz, P. Organometallics, 1990, 9, 2262. (b) Schaverien, C. J.; Dewan, J. C.; Schrock, R. R. f. Am. Chern. Soc. 1986, 108, 2771. 6. Cummins, C. C.; Baxter, S. M.; Wolczanski, P. T. f. Am . Chern. Soc. 1988, 110, 8731. 7. For other imido complexes, see: (a) Hill, J. E.; Profilet, R. D.; Fanwick, P. E.; Rothwell, I. P. Angew. 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Comments lnorg. Chern. 1988, 8, 125. 14. (a) Glueck, D. S.; Wu, J.; Hollander, F. J.; Bergman, R. G. f. Am . Chern. Soc. 1991, 113, 2041. (b) Glueck, D. S.; Hollander, F. J.; Bergman, R. G. f. Am. Chern. Soc. 1989, 111, 2719. 15. de With, J.; Horton, A . D. Angew. Chern. Int. Ed. Engl. 1993, 6, 32, 16. Thompson, M. E.; Baxter, S. M.; Bulls, A. R.; Burger, B. J.; Nolan, M. C.; Santarsiero, B. D.; Schaefer, W. P.; Bercaw, J. E. f. Am. Chern . Soc. 1987, 109, 203. 17. Huber, S. R.; Baldwin, T. C.; Wigley, D. E. Organometallics 1993, 12, 91. 18. (a) Parkin, G.; Marsh, R. E.; Schaefer, W. P.; Bercaw, J. E. Inorg. Chern. 1988, 27, 3262. (b) Parkin, G.; Bercaw, J. E. Polyhedron 1988, 7, 2053. 19. (a) Williams, D. S.; Schrock, R. R. Organometallics 1993, 12, 1148. (b) Williams, D. S.; Anhaus, J. T.; Schofield, M. H .; Schrock, R. R.; Davis, W. M. f. Am. Chern. Soc. 1991, 113, 5480. (c) Williams, D. S.; Schofield, M. H.; Anhaus, J. T.; Schrock, R. R. f. Am. Chern . Soc. 1990, 112, 6728. 20. Other replacements for the cyclopentadienyl unit include the Khiui, tris-pyrazolylborate, and carborane ligands: (a) Kelson, E. P.; Henling, L. M .; Schaefer, W. P.; Labinger, J. A .; Bercaw, J. E. Inorg. Chern. 1993, 32, 2863. (b) Power, J.P.; Evertz, K.; Henling, L. M .; Marsh, R.; Schaefer, W. P.; Labinger, J. A.; Bercaw, J. E. Inorg. Chern. 1990, 29, 5058. (c) Klaui, W. Angew. Chern. Int. Ed. Engl. 1990, 29, 627. (d) Feng, X.; Bott, S. G.; Lippard, S. L. J. Am. Chern. Soc. 1989, 111, 8046. (e) Klaui, W .; Muller, A.; Eberspach, W.; Boese, R.; Goldberg, I. f. Am. Chern. Soc. 1987, 109, 164. (f) Grimes, R. M. Chern. Rev. 1992, 92, 251. (g) Trofimenko, S. Chern. Rev. 1993,93, 943. (h) Calabrese, J. C.; Trofimenko, S.; Thompson, J. S. f. Chern . Soc. , Chern . Commun. 1986, 1122. (i) For recent work on tridentate ligands: Abstracts 289-297. 206th ACS National Meeting, Chicago, Illinois, 1993. 21. Williams, D. N.; Mitchell, J. P.; Poole, A. D.; Siemeling, U.; Clegg, W.; Hockless, D. C. R.; O'Neil, P. A. 0.; Gibson, V. C. f. Chern . Soc. Dalton . Trans. 1992, 739. 22. Lauher, J. W .; Hoffmann, R. f. Am. Chern. Soc. 1976, 98, 1729. 23. Schaller, C. P.; Bennett, J. L.; Wolczanski, P. T. Abstract 453. 204th ACS National Meeting, Washington, D. C., 1992. 73 24. (a) Gibson, V. C.; Bercaw, J. E.; Bruton, W . J., Jr.; Sanner, R. D. Organometallics 1986, 5, 976. (b) Sanner, R. D.; Bruton, W. J. , Jr. f. Organomet. Chern . 1982, 240, 157. 25. Williams, D. N.; Mitchell, J. P.; Poole, A. D.; Siemeling, U.; Clegg, W .; Hockless, D. C. R.; O'Neil, P. A .; Gibson, V. C. f. Chern . Soc ., Dalton Trans . 1992, 739. 26. Bryson, N.; Youinou, M.-T.; Osborn, J. A. Organometallics 1991, 10, 3389. 27. Nugent, W. A.; Harlow, R. L. f. Chern. Soc. , Chern. Commun . 1978, 579. 28. Churchill, M. R.; Wasserman, H. J. lnorg . Chern. 1982,21, 223. 29. Gibson, V. C.; Kee, T. P.; Clegg, W. f . Chern . Soc. Chern . Commun . 1990, 29. 30. Michelman, R. I.; Andersen, R. A .; Bergman, R. G . f. Am . Chern. Soc . 1991, 113, 5100. 31 de With, J.; Horton, A. D. Organometallics 1990, 9, 2207. 32. Chan, D. M. -T.; Fultz, W . C.; Nugent, W . A .; Roe, D. C.; Tulip, T. H . f . Am. Chern. Soc . 1985, 107, 251. 33. (a) Simpson, R. D.; Bergman, R. G. Organometallics 1992, 11 , 4306. (b) Hartwig, J. F.; Bergman, R. G.; Andersen, R. A. f . Am. Chern. Soc. 1991, 113, 6499. (c) Buhro, W . E.; Chisholm, M. H.; Martin, J. D.; Huffman, J. C.; Felting, K.; Streib, W . E. f. Am . Chern . Soc. 1989, 111, 8149. (d) Chisholm, M. H.; Extine, M.; Cotton, F. A .; Stults, B. R. f . Am. Chern . Soc. 1976, 98, 4683. (e) Chisholm, M. H.; Extine, M. W. f. Am. Chern. Soc. 1977, 99, 782. (f) Chisholm, M . H.; Extine, M. W . f. Am . Chern. Soc . 1977, 99, 792. 34. (a) Pilato, R. S.; Housmekerides, C. E.; Jernakoff, P.; Rubin, D.; Geoffroy, G. L.; Rheingold, A. L. Organometallics 1990, 9, 2333. (b) Jernakoff, P.; Geoffroy, G . L.; Rheingold, A. L.; Geib, S. J. f. Chern. Soc., Chern . Commun . 1987, 1610. (c) reference 14. 35. (a) Chisholm, M . H.; Extine, M . W . f. Am. Chern. Soc. 1977, 99, 782. (b) Chisholm, M. H.; Extine, M. W. f. Am. Chern. Soc. 1977, 99, 792. 36. Cyclometallacarbamates are proposed as intermediates in the 74 preparation of imido complexes from metal oxo complexes and an isocyanate. See reference 2a for a review. 37. Danopoulos, A. A.; Wilkinson, G .; Hussainbates, B.; Hursthouse, M . B. f. Chern. Soc. , Dalton Trans. 1991, 269. (b) Green, M. L. H.; Hogarth, G.; Konidaris, P. C.; Mountford, P. f. Chern. Soc., Dalton Trans. 1990, 3781. 38. Baldwin, T. C.; Huber, S. R.; Bruck, M. A.; Wigley, D . E. Manuscript submitted to fnorg. Chern. Recently, prepared [Li(THF)][Cp*Ta(=NPh'hCl] where Ph' = 2,6-diisopropylphenyl from Cp*TaCl4 and lithium 2,6-diisopropylanilide in THF. Furthermore, the complex has been found to be rather unreactive. 39. Burger, B.J.; Bercaw, J. E. In Experimental Organometallic Chemistry; Wayda, A. L., Darensbourg, M. Y. Eds.; ACS Symposium Series 357; American Chemical Society, Washington, D. C. 1987. 40. Marvich, R. H.; Brintzinger, H. H. f. Am. Chern. Soc. 1971, 93 , 2046. 41. International Tables for X-ray Crystallography, Volume IV, p. 71, p. 147; Birmingham, Kynoch Press, 1974. 73 Appendix 2. X-ray crystal structure data for Cp*Ta(=NPh)(NHPhh (32) and Cp*Ta(NPhOC)(OCONHPh)z (36). Table VI. Crystal and Intensity Collection Data for Cp*Ta(=NPh)(NHPhh (32). chemical formula crystal dimensions, mm crystal system space group CzsH32N3Ta a,A 12.343 (4) b,A 14.584 (6) c, A 15.104 (5) l3,deg 109.35 (2) v, A3 2565.3 (16) Peale, g cm- 3 1.532 z 4 t..,A 0.711 IJ., cm-1 42.52 temp, oc 23 28 rang, deg 2-48 no. of reflections measured, total no. of reflections measured, unique 8700 R 0.023 GOF 1.52 0.53 X 1.05 X 1.35 monoclinic P21/c 4018 76 Table VII. Final Heavy Atom Parameters for Cp*Ta(=NPh)(NHPhh (32) . :c,y,z a.nd Ue 9 ° X 104 Atom :c y z Ueq Ta 2537(.1) 668( .1) 4125(.1) 506 N1 1874(3) 1671(2) 4385(2) 551(9) N2 4157(3) 1105(3) 4366(3) 701(11) N3 2610(3) -202(2) 5192(2) 633(10) C1 1148( 4) 2387(3) 4409(3) 515(11) C2 1366( 4) 3271(3) 4190(3) 728(14) C3 621(6) 3974(4) 4200(4) 958(19) C4 -347(6) 3813(5) 4414(4) 1004(20) C5 -571( 4) 2941(5) 4640( 4) 981(18) C6 171( 4) 2233(3) 4641(3) 760(14) Cll 4694(4) 1959(3) 4534(3) 617(12) C12 5524( 4) 2182(4) 4123(3) 737(14) C13 6073(4) 3012(4) 4276(4) 837(16) C14 5809(5) 3646(4) 4835(4) 904(18) C15 4988(5) 3451(4) 5244(4) 837(16) C16 4439(4) 2615(3) 5106(3) 707(13) C21 2752(3) - 63(3) 6138(3) 531(11) C22 3031(4) 797(3) 6555(3) 621(12) C23 3236(4) 908(3) 7501(3) 677(13) C24 3156(4) 188(4) 8059(3) 706(13) 77 Table VII. (Continued) Ueq Atom z y z C25 2861( 4) -666(3) 7653(3) 707(13) C26 2651( 4) -788(3) 6708(3) 601(12) C31 2057( 4) -737(3) 3133(3) 699(14) C32 2757( 4) -202(5) 2781( 4) 822(16) C33 2183(5) 629( 4) 2464(3) 757(14) C34 1106(4) 586(3) 2602(3) 643(12) C35 1048( 4) -251(3) 3037(3) 594(12) C36 2277(5) -1709(4) 3475(4) 1187(22) C37 3938(6) -492(6) 2748(6) 1627(29) C38 2576(6) 1400(5) 1961( 4) 1448(25) C39 174(5) 1295( 4) 2279( 4) 982(18) C40 48(5) -592(4) 3300(4) 960(17) Cl Ueq = i Li L;[U,;(a;aj)(a,. a;)] 78 Table VIII. Anisotropic Displacement Parameters for Cp"la(==NPh)(NHPh)2 (32). Atom Uu ul2 u33 Ta N1 N2 N3 C1 C2 C3 C4 C5 C6 C11 C12 C13 C14 C15 C16 C21 C22 C23 C24 C25 C26 C31 C32 C33 C34 C35 C36 C37 C38 C39 C40 526~1) 579 22) 462~1) 543 22) 823 27 614 28 Uu Uu 479~1) 494 19) 43~1) 4 17) 128 17) 96~1) -81~1) -25 16) 419 20 465 26 611 23 429 22 94 19 84 21 177 20 122 20 -73?17 -40 18 1429 59 1116 52 539 32 855 45 827 38 878 41 195 36 501 40 837 36 508 27 623 31 633 33 629 30 803 37 854 35 616~27 702 31 50 27 59 23 115 28 839 41 826 38 709 38 748 36 928 41 821 35 -156 31 -39 30 474 26 715 30 543 27 513 29 515 26 595 27 84 19 7 22 735 33 728 32 758 34 670 31 129 27 56 27 100 26 -38 32 -285 34 592n 563n 89rl 4 rl 958n 510n 763n 97n 730 36l 1103n 114lf46l 188n 68rl 92rl 824n -lrl 63ln 76rl 686n -109n 74ln 536n 674n 3 rl 597n 28l 16n 693n 608n Slrl 29n 908n 2335t8l 1713t8l -92n U23 16rl -173(20l 75n 353n -210n 15rl 133n 349~28) 266 40~ 111 37 86 27 -110 34 341 30 56 22 107 25 -23 25 -15 23 14(26 -24 33 116 31 17 81 20 164 23 88 32 -211 29 rl 125n 785 34 631 34 993( 41 484 27 1058 44 749 34 sun 556 28 721 31 654 623 27 726 34 488 25 544 28 1445 56 585 27 663 37 531 25 981 42 -65 23 222 35 120 25 239 26 154 -44 25 156 29 191 26) 41~22) 16 22~ -234(37 1856 72 1117 46 771{36) 1654 67 777 38 1125(46) 852 42 748 34 826(36) -1023 57 194 33 -192(33) 471 46 -100 31 51(29) 22l -248~ 26~ -47 20 -22(21 ) -106 ~ 22 ~ 38 26 120(2 7) -22(22 ) -145(23 ) -461(32) -151 (26 ) -77(23) -44(21) -204{32 ) -174 42 ~ 25 28 100(32) 533n -128lt4) u,,j values have been multiplied by 10' The form of the displacement factor is: 2 exp -27r (U11 h 2 a•' + U 22 k 2 b•' + U33 l 2 c•' + 2U12 hka•b• + 2Uuhla•c• + 2U23kfb•c• ) 79 Table IX. Complete Distances and Angles for Cplt'fa(=NPh)(NHPhh (32). Distance( A) Ta Ta Ta Ta Ta Ta Ta Ta Ta -Cp* -N1 -N2 -N3 -C31 -C32 -C33 -C34 -C35 N1 -C1 N2 -Cll N3 -C21 C1 -C2 C1 -C6 C2 -C3 C3 -C4 C4 -C5 C5 -C6 Cll -C12 Cll -C16 C12 -C13 C13 -C14 C14 -C15 C15 -C16 C21 -C22 C21 -C26 C22 -C23 C23 -C24 C24 -C25 C25 -C26 C31 -C32 C31 -C35 C31 -C36 C32 -C33 C32 -C37 C33 -C34 C33 -C38 C34 -C35 C34 -C39 C35 -C40 2.126{3) 1. 784(5) 2.013(5) 2.029(5) 2.491(7) 2.484{6) 2.401( 6) 2.395(5) 2.423(7) 1.383(6) 1.395(6) 1.395(6) 1.379(8) 1.382(7) 1.381(9) 1.357(9) 1.368(8) 1.381(7) 1.401(8) 1.392(6) 1.370(8) 1.362(8) 1.380(7) 1.376(6) 1.395(6) 1.395(7) 1.377(7) 1.369(7) 1.383(6) 1.374(6) 1.393(8) 1.399(8) 1.503(10) 1.406(7) 1.534(9) 1.413(6) 1.523(7) 1.399(7) 1.503(7) 1.501(6) Distance( A) N2 -HN2 N3 -HN3 C2 -H2 C3 -H3 C4 -H4 C5 -HS C6 -H6 C12 -H12 C13 -H13 C14 -H14 C15 -H15 C16 -H16 C22 -H22 C23 -H23 C24 -H24 C25 -H25 C26 -H26 C36 -H36A C36 -H36B C36 -H36C C37 -H37A C37 -H37B C37 -H37C C38 -H38A C38 -H38B C38 -H38C C39 -H39A C39 -H39B C39 -H39C C40 -H40A C40 -H40B C40 -H40C 0.974 0.972 0.950 0.947 0.950 0.952 0.951 0.949 0.947 0.947 0.956 0.951 0.951 0.951 0.950 0.952 0.952 0.948 0.948 0.950 0.946 0.957 0.934 0.947 0.938 0.952 0.943 0.948 0.954 0.950 0.947 0.947 80 Table IX. (Continued) Angle( 0 ) N1 N1 N1 N2 N2 N3 -Ta. -Ta. -Ta. -Ta. -Ta. -Ta. -N2 -N3 -Cp* -N3 -Cp* -Cp* Ta. -N1 -C1 Ta. -N2 -C11 Ta. -N3 -C21 C2 -C1 -N1 C6 -C1 -N1 C6 -C1 -C2 C3 -C2 -C1 C4 -C3 -C2 C5 -C4 -C3 C6 -C5 -C4 C5 -C6 -C1 C12 -C11 -N2 C16 -C11 -N2 C16 -C11 -C12 C13 -C12 -C11 C14 -C13 -C12 C15 -C14 -C13 C16 -C15 -C14 C15 -C16 -C11 C22 -C21 -N3 C26 -C21 -N3 C26 -C21 -C22 C23 - C22 -C21 C24 -C23 -C22 C25 -C24 -C23 C26 -C25 -C24 C25 -C26 -C21 C35 - C31 -C32 C36 -C31 -C32 C36 -C31 - C35 C33 -C32 -C31 C37 - C32 -C31 C37 -C32 -C33 C34 -C33 -C32 101.6(2) 103.9(2) 120.2(2) 106.0(2) 112.7(2) 111.1(2) 166.7(4) 134.4(3) 132.9(3) 121.3(5) 120. 7( 4) 117.9(5) 120.6(6) 121.1(6) 119.1(6) 120.4(5) 120.8( 4) 119.9( 4) 122.4( 4) 117.7(5) 121.6(5) 119.8(5) 120.0(5) 120.8( 4) 120.1( 4) 121.4( 4) 121.0( 4) 117.6( 4) 120.5( 4) 121.5(5) 118.7( 4) 120.6( 4) 121.2( 4) 108.7(5) 126.5(5) 124.5(6) 107.8(5) 125.1(5) 127.1(5) 107.7( 4) Angle( 0 ) C38 -C33 -C32 C38 -C33 -C34 C35 -C34 -C33 C39 -C34 -C33 C39 -C34 -C35 C34 -C35 -C31 C40 -C35 -C31 C40 -C35 -C34 HN2 -N2 -C11 HN3 -N3 -C21 H2 -C2 -C1 H2 -C2 -C3 H3 -C3 -C2 H3 -C3 -C4 H4 -C4 -C3 H4 - C4 -C5 H5 -C5 -C4 H5 -C5 - C6 H6 -C6 -C1 H6 -C6 - C5 H12 -C12 -C11 H12 -C12 -C13 H13 - C13 -C12 H13 - Cl3 -C14 H14 - C14 -C13 H14 - C14 -C15 H15 -C15 -C14 H15 - C15 - C16 H16 - C16 -C11 H16 -C16 - C15 H22 - C22 - C21 H22 -C22 -C23 H23 - C23 -C22 H23 - C23 -C24 H24 -C24 -C23 H24 - C24 - C25 H25 - C25 - C24 H25 -C25 - C26 H26 - C26 - C21 H26 - C26 - C25 126.8( 4) 125 .2(4) 107.8( 4) 125.3(4) 126 .8( 4) 107.9(5) 125.9(5) 126.1( 5) 112.7 113.3 119.3 120.1 119 .1 119.9 120.3 120.5 119.8 119.7 119.4 119.7 119.3 119.1 120.3 119.9 120.1 119.9 119.7 119.5 120.2 119.7 120.1 119.5 119.1 119.4 120.4 120 .9 119.0 120.4 119.7 119.2 81 Table IX. (Continued) Angle( 0 ) H36A -C36 -C31 H36B -C36 -C31 H36C -C36 -C31 H36B -C36 -H36A H36C -C36 -H36A H36C -C36 -H36B H37 A -C37 -C32 H37B -C37 -C32 H37C -C37 -C32 H37B -C37 -H37 A H37C -C37 -H37 A H37C -C37 -H37B H38A -C38 -C33 H38B -C38 -C33 H38C -C38 -C33 H38B -C38 -H38A H38C -C38 -H38A H38C -C38 -H38B H39A -C39 -C34 H39B -C39 -C34 H39C -C39 -C34 H39B -C39 -H39A H39C -C39 -H39A H39C -C39 -H39B H40A -C40 -C35 H40B -C40 -C35 H40C -C40 -C35 H40B -C40 -H40A H40C -C40 -H40A H40C - C40 -H40B 108.5 108.5 108.4 110.6 110.4 110.4 108.3 107.0 108.1 110.1 112.0 111.1 107.8 108.0 107.5 111.7 110.5 111.2 108.7 108.5 108.1 111.0 110.4 110.0 108.2 108.3 108.4 110.6 110.5 110.7 82 Table X. Assigned Hydrogen Atom Parameters for Cp''Ta(=NPh)(NHPhh ( 32). z, y and z x 10 4 Atom z y z B HN2 HN3 H2 H3 H4 H5 H6 H12 H13 H14 H15 H16 H22 H23 H24 H25 H26 H36A H36B H36C H37A H37B H37C H38A H38B H38C H39A H39B H39C H40A H40B H40C 4685 2525 2039 790 -860 -1243 9 5716 6630 6191 4796 3886 3090 3440 3304 2806 2438 3075 2028 1856 4275 3811 4378 2274 2301 3393 -289 -262 529 325 -284 -489 609 -844 3394 4576 4300 2822 1630 1745 3150 4219 3901 2488 1312 1498 277 -1169 -1380 -1781 -2106 -1823 19 -975 -696 1956 1275 1411 1262 1174 1883 -778 -1094 -108 4366 5010 4037 4051 4408 4798 4804 3733 3989 4946 5627 5402 6186 7774 8711 8037 6441 3794 2950 3889 2554 2297 3345 2104 1316 2194 2665 1644 2332 3939 2907 3215 6.0 5.4 6.3 8.4 8.6 8.5 6.6 6.4 7.2 7.8 7.2 6.1 5.3 5.9 6.1 6.1 5.3 10.3 10.3 10.3 14.1 14.1 14.1 12.6 12.6 12.6 8.4 8.4 8.4 8.4 8.4 8.4 83 Table XI. Crystal and Intensity Collection Data for Cp''Ta(OCONPh)(T)2-QCONHPhh (36). chemical formula crystal dimensions, mm crystal system space group C31H3~306Ta•2(C4HsO) a,A 12.2094 (12) b,A 15.8783 (13) c, A 19.7276 (12) ~, deg 102.329 (6) V, A3 3736.3 (5) Peale, g crn-3 1.543 z 4 J..,A 0.711 J.l, mm-1 2.960 temp, K 28 rang, deg 163 no. of reflections measured, total R GOF 11,846 0.36 X 0.42 X 0.47 monoclinic P2dn 4-55 0.047 1.49 84 Table XII. Final Heavy Atom Parameters for Cp"Ta(OCONPh)(ll2-0CONHPhh (36). Atomic Coordinates (X lOS) Equivalent isotropic displacement coefficients (A2 X 104) y z U(eq) 18548(1) 11502(1) 2 70 (1) 0( 1) 9718(2) 6933(30) 19515(20) 1084(17) 294(11) 0(2) -9673(34) 16902(22) -6205(17) 345(13) 0( 3) 8942(32) 5265(22) 8363(17) 322(12) 0(4) 5170(31) 9179(21) 18184(16) 295(11) 0(5) 3092(34) 25231(22) 19156(17) 341(13) 0(6) 4473(33) 31913(21) 9806(17) 307(11) N( 1) -7224(36) 17233(25) 5971(21) 276(13) N(2) 2033(37) -4654(26) 14557(20) 306(14) N(3) -3527(42) 38624(27) 17966(22) 364(16) C(1) 27295(47) 25059(36) 10385(31) 391(19) C(2) 28561(46) 16270(37) 9855(30) 367(18) C(3) 28401(49) 12748(36) 16424(31) 401(19) C(4) 26762(53) 19313(37) 20859(32) 442(20) C(5) 26136(49) 26941(35) 17129(30) 392(19) C(6) 27884(60) 31351(39) 4810(37) 536(24) C( 7) 30132(56) 11601(46) 3555(35) 560(26) C(8) 30673(59) 3707 (39) 18542(40) 577(26) C(9) 26310(65) 18265(44) 28357(33) 583(26) C(10) 25560(61) 35759(40) 19987(37) 585(26) C( 11) -4110(46) 17798(29) -269(26) 288(16) C(12) -17534(44) 14577(31) 7061(26) 299(16) C( 13) -26136(50) 11211 ( 36) 1816(30) 407(20) C(14) -36043(58) 8663(45) 3359(35) 539(24) C(15) - 37881(50) 9197(44) 10011(36) 511(24) C(16) -29645(54) 12475(40) 15092(33) 471(22) C(17) - 19618(51) 15238(37) 13705(29) 385(19) X Ta(1) 85 Table XII. (Continued) C(18) 5334(45) 3184(31) 13757(25) 294(16) C(19) -1675(45) -8236(32) 20315(26) 309(16) C(20) -1738(50) -17008(34) 20528(30) 382(19) C(21) -4383(57) -21048(40) 26244 (32) 466(22) C(22) -7083(61) -16305(42) 31519(33) 519(24) C(23) -7205(59) -7650(41) 31182(31) 490(23) C(24) -4474(49) -3487(36) 25589(27) 385(19) C(25) 1266(49) 32029(32) 15454(26) 336(17) C(26) -5271(48) 46808(32) 15136(26) 343(17) C(27) -12157(64) 51979(40) 17962(32) 518(24) C(28) -13809 (70) 60196(43) 15672(35) 627(29) C(29) -8878(61) 63339(37) 10645(30) 500(23) C(30) - 2119(53) 58127(37) 7753(31) 444(21) C(31) -258(51) 49751(36) 9981(29) 402(20) 0(7) 55337(46) 87802(36) 18136(24) 649(20) C(32) 65750(78) 87093(57) 16367(48) 792(37) C(33) 66838(94) 78084(72) 15143(65) 1119(56) C(34A) 56545(242) 73795(155) 14133(124) 964(109) C(34B) 55007(230) 76595(130) 10335(96) 864(93) C(35) 48241(79) 81380(71) 14526(41) 913(46) 0(8) 59560(46) 39920(32) 1792(28) 722(22) C(36) 63872(87) 46831(55) -1299(58) 1041(49) C(37) 71949(82) 44014(53) -4950(50) 848(39) C(38) 74885(77) 35143(50) -2412(47) 769(36) C(39) 68350(66) 33975(46) 3008(41) 604(28) * Equivalent isotropic U defined as one third of the trace of the orthogonalized uij tensor 86 Table XIII. Complete Distances for Cp*Ta(OCONPh)(T12-QCONHPhh (36) . Ta(l)-0(1) 2.016(3) Ta(1)-0(3) 2.195(3) Ta(l)-0(4) 2 . 138(3) Ta(1)-0(5) 2 . 140(4) Ta(l)-0(6) 2 . 221(3) Ta(l)-N(l) 2.133(4) Ta(l)-C(1) 2.434(6) Ta(1)-C(2) 2.418(6) Ta(1)-C(3) 2 . 459(6) Ta(1)-C(4) 2 . 472(6) Ta(1)-C(5) 2 . 465(6) Ta(1)-C(11) 2.566(5) Ta(1)-C(18) 2.557(5) Ta(1)-C(25) 2 . 569(6) Ta(1)-Cnt 2.137 0(1) -C(11) 1. 345(7) 0(2)-C(11) 1.230(6) 0(3)-C(18) 1.279(7) 0(4)-C(18) 1.295(6) 0(5)-C(25) 1.296(6) 0(6)-C(25) 1.258(7) N(1)-C(11) 1.367(7) N(1)-C(12) 1.387(7) N(2)-C(18) 1.328(7) N(2)-C(19) 1.428(7) N(3)-C(25) 1.345(7) N(3) -C(2 6) 1.412(7) C(1)-C(2) 1.410(8) C(1)-C(5) 1. 400(9) C(1)-C(6) 1 . 499(9) C(2)-C(3) 1.415(9) C(2) -C(7) 1 . 494(10) C(3) -C(4) 1.403(9) C(3)-C(8) 1. 504(8) C(4)-C(5) 1.411(8) C(4)-C(9) 1.501(9) C(5)-C(10) 1.517(9) C(12)-C(13) 1.412(7) C(12)-C(17) 1.392(8) C( 13) -C(14) 1.370(10) C(14)-C(15) 1.381(10) C(15) -C(l6) 1. 363(8) C(16)-C(17) 1.382(9) C(19)-C(20) 1. 394(7) C(19)-C(24) 1.386(8) C(20)-C(21) 1.394(9) C(21)-C(22) 1.380(10) C(22)-C(23) 1. 376 (9) C(23)-C(24) 1.387(9) C(26) -C(27) 1. 376(9) C(26)-C(31) 1.376(9) C(27)-C(28) 1. 381(9) C(28)-C(29) 1.360(11) C(29) -C(30) 1. 376(10) C(30) -C(31) 1. 404(8) 87 Table XIII. (Continued) 0(7)-C(32) 1.393(12) 0(7) -C(35) 1.426(11) C(32) -C(33) 1.461(15) C(33)-C(34A) 1.406(31) C(33) -C(34B) 1.568(26) C(34A) -C(35) 1.587(29) C(34B) -C(35) 1.495(27) 0(8)-C(36) 1.411(12) 0(8)-C(39) 1.411(9) C(36)-C(37) 1.412(16) C(37) -C(38) 1.512(12) C(38) -C(39) 1.476(13) * Cnt is the centroid of the C(1)-C(S) ring . 88 Table XIV. Complete Angles for Cp't'fa(OCONPh)(T\2-0CONHPhh (36) . 0(1) -Ta(1) -0(3) 78.3(1) 0(1)-Ta(1)-0(4) 132.2 ( 1) 0(3) -Ta(l) -0(4) 60.3(1) 0(1)-Ta(1)-0(5) 132 . 4(1) 0(3) -Ta(1) -0(5) 132.5(1) 0(4)-Ta(1)-0(5) 73 . 9(1) 0(1)-Ta(1)-0(6) 78.1(1) 0(3)-Ta(1)-0(6) 151.9(1) 0(4)-Ta(1)-0(6) 0(1) -Ta(1) -N(1) 130.8(1) 63 . 4(2) 0(5)-Ta(1)-0(6) 0(3) -Ta(1) -N(1) 59 . 5(1) 77 . 5 ( 1 ) 0(4)-Ta(1)-N(1) 84.0(1) 0(5)-Ta(1)-N(1) 86 . 4 ( 2 ) 0(6)-Ta(1)-N(1) 78.4(1) Cnt-Ta(1)-0(1) 104 .7 Cnt-Ta(1)-0(3) 100.2 Cnt-Ta(1)-0(4) 105 . 2 Cnt-Ta(1)-0(5) 103.3 Cnt-Ta(1)-0(6) 100 . 3 Cnt-Ta(1)-N(1) 168.0 Ta(1)-0(1)-C(11) 97.5(3) Ta(1)-0(3)-C(18) 90.9 ( 3) Ta(1)-0(4)-C(18) 93.0(3) Ta(1)-0(5)-C(25) 93 . 5 ( 3 ) Ta(1)-0(6)-C(25) 90.8(3) Ta(1)-N(1)-C(11) 91.6 ( 3 ) Ta(1)-N(1)-C(12) 139.8(3) C(11)-N(1)-C(12) 126 . 6 (4 ) C(18)-N(2)-C(19) 128 . 6(4) C(25)-N(3)-C(26) 127 . 7 ( 5) C(2)-C(1)-C(5) 108.5(5) C(2)-C(1)-C(6) 125 . 6 ( 6) C(5)-C(1)-C(6) 125.8(5) C(1)-C(2)-C(3) 107 . 4 ( 5) C(1) -C(2) -C(7) 126 . 0(6) C(3) - C(2) - C(7) 126 . 5(6) C(2)-C(3)-C(4) 108 . 0(5) C(2)-C(3)-C(8) 126 . 4(6 ) C(4) -C(3) -C(8) 125.3(6) C(3) - C(4) -C(5) 108 . 2 ( 6) C(3)-C(4)-C(9) 124.9(6) C(5)-C(4)-C(9) 126 . 9 ( 6) C(1) - C(5)-C(4) 107 . 9(5) C(1)-C(5)-C(10) 124 . 9 ( 5) C(4)-C(5)-C(10) 126.9(6) 0(1) - C(ll)-0(2) 122.6 ( 5) 0(1) -C(ll) -N(1) 107 . 1(4) 0(2) -C(ll) -N(1) 130 . 3 ( 5) N(1) - C(12)-C(13) 124.0(5) N(1)-C(12)-C(17) 118.5(4 ) C( 13)-C(12)-C(17) 117 . 5(5) C(12)-C(13)-C(14) 120 . 2(6) C(13)-C(14)-C(15) 121. 6(6) C(14) - C(15)-C(16) 118.6 ( 6 ) C(15)-C(16)-C(17) 121.4(6) C(12) - C(l7)-C(16) 120 . 7(5) 89 Table XIV. (Continued) 0 ( 3)-C(18)-0(4) 115.4(4) 0(3) -C(18) -N(2) 120 . 6(5) 0(4)-C(18)-N(2) 124 . 1(5) N(2)-C(19)-C(20) 115 . 3(5) N(2)-C(19)-C(24) 123 . 5(5) C(20)-C(19)-C(24) 121.2(5) C(19)-C(20)-C(21) 119.2(6) C(20)-C(21)-C(22) 119.5(6) C(21)-C(22)-C(23) C(19) - C(24)-C(23) 120 . 7(6) 118 . 5(5) C(22)-C(23)-C(24) 120 . 8(6) 0(5)-C(25)-0(6) 116 . 0(5) 0(5)-C(25)-N(3) 118 . 5(5) 0(6)-C(25)-N(3) 125 . 5(5) N(3)-C(26)-C(27) 116 . 3(5) N(3)-C(26)-C(31) 123 . 5(5) C( 27)-C(26)-C(31) 120 . 2(5) C(26)-C(27)-C(28) 119.4(7) C(27)-C(28)-C(29) 121.9(7) C(28)-C(29)-C(30) 118 . 7 ( 6) C(29)-C(30)-C(31) 120 . 8(6) C(26)-C(31)-C(30) 119 . 0(6) C(32)-0(7)-C(35) 107 . 9(7) 0(7)-C(32)-C(33) 103 . 9(8) C(32)-C(33)-C(34A) 112.8(14) C(32)-C(33)-C(34B) 98 . 2(11 ) C(33)-C(34A)-C(35) 100.8(16) C(33)-C(34B)-C(35) 97 . 8(12 ) 0(7)-C(35)-C(34A) 103.9(11) 0(7)-C(35)-C(34B) 106 . 9(11 ) C(36)-0(8)-C(39) 104 . 7 (7) 0(8)-C(36)-C(37) 109 . 9(7) C(36)-C(37)-C(38) 105.6(8) C(37)-C(38)-C(39) 103 . 3(8) 0(8)-C(39)-C(38) 107 . 6(6) 90 Table XV. Assigned Hydrogen Atom Parameters for Cp't'fa(OCONPh)('r12-0CONHPhh (36). H-Atom coordinates (X 104) Isotropic displacement coefficients (A2 X 104) X y z u H(2A) 213 -817 . 1099 800 H(3A) -594 3771 2191 800 H(6A) 3550 3316 523 800 H(6B) 2525 2882 34 800 H(6C) 2328 3612 529 800 H(7A) 3797 1116 354 800 H(7B) 2700 606 362 800 H(7C) 2635 1452 -54 800 H(8A) 3856 298 2034 800 H(8B) 2663 218 2203 800 H(8C) 2833 18 1454 800 H(9A) 3373 1873 3119 800 H(9B) 2163 2259 2962 800 H(9C) 2325 1284 2906 800 H(10A) 3303 3767 2193 800 H(10B) 2210 3948 1631 800 H(10C) 2125 3572 2353 800 H(13A) -2500 1077 -284 800 H(14A) -4177 630 -23 800 H(l5A) -4489 747 1104 800 H(16A) -3079 1284 1975 800 H(17A) -1395 1756 1736 800 H(20A) 5 -2019 1677 800 H(21A) -444 -2709 2646 800 H(22A) -883 -1907 3548 800 H(23A) -917 -447 3489 800 H(24A) -462 255 2533 800 H(27A) -1580 4987 2148 800 91 Table XV. (Continued) H(28A) -1856 6380 1770 800 H(29A) -1013 6907 912 800 H(30A) 143 6025 420 800 H(31A) 443 4613 792 800 H(32A) 7160 8907 2008 800 H(32B) 6597 9021 1223 800 H(33A) 7161 7562 1915 800 H(33B) 7023 7717 1124 800 H(34A) 5622 6961 1759 800 H(34B) 5480 7121 963 800 H(34C) 5302 7074 981 800 H(34D) 5451 7910 585 800 H(35A) 4454 8322 998 800 H(35B) 4267 7974 1705 800 H(36A) 6727 5075 224 800 H(36B) 5784 4965 -438 800 H(37A) 7841 4762 -409 800 H(37B) 6882 4391 -985 800 H(38A) 8277 3473 -45 800 H(38B) 7291 3105 -605 800 H(39A) 6535 2837 276 800 H(39B) 7297 3481 754 800 92 Chapter 4 Polymerization and Heterolytic Cleavage Reactions with Zirconium Borollide Complexes ABSTRACT ............. ........ .... .. ......................... ... .. ... ... . ..... ... .... .. ... 93 INTRODUCTION ....................................................................... 94 RESULTS AND DISCUSSION ............................................... 103 CONCLUSION ................. .. .............. .. .. .. .. ................................. 111 EXPERIMENTAL 113 REFERENCES ............................................................................ 123 APPENDIX III ............................................................................ 127 93 Abstract: The preparation and reactivity of several zirconium complexes with the borollide ligand, (C4H4BNiPrz)2-, is described. The ligand is introduced by treating Cp*ZrCb with one equivalent of Liz(C4H4BNiPrz)·THF to generate Cp*(C4H4BNiPrz)ZrCl·LiCl. This complex contains a 115_ coordinated borollide ligand, as shown by an X-ray crystal structure analysis . Alkylation and arylation with trimethylsilylmethyllithium, benzylpotassium or phenyllithium yielded Cp*(C4H4BNiPr2)ZrR complexes. These catalysts polymerizes ethylene, but only oligomerizes a-olefins. In addition, Cp*(C4H4BNiPrz)ZrCl·LiCl has been found to exhibit the formal heteroly tic cleavage of HCl and CH3I, affording Cp*(C4H4BNHiPrz)ZrClz and Cp*(C4H4BN(CH3)iPrz)ZrCl(I), respectively. Finally, treatment of C p*(C4H4BNiPrz)ZrCl·LiCl with LiNHtBu generated the zwitterionic complex, Cp*(C4H4BNHiPrz)Zr=NtBu. 94 Introduction The cyclopentadienyl (Cp) ligand and its analogues have been the foundation for the synthesis of many organometallic complexes.l With electron-donating groups, the ligand is capable of stabilizing high oxidation states (see Chapters 2 and 3) and substitution on the Cp ring allows for catalytic stereoselectivity.2 Furthermore, many cyclopentadienyl complexes serve as catalysts for various organic transformations, including hydrogenation,3 hydroamination,4 and hydroborationS of olefins and imines. One area in which metallocene complexes have proved especially successful is Ziegler-Natta polymerization. Nearly forty years ago, Ziegler discovered that zirconium acetylacetonate in the presence of the co-catalyst, triethylaluminum, readily polymerized ethylene.6 Subsequent work by Natta extended this process to propylene polymerizations? Today, over 8 billion pounds of polyethylene is produced yearly using catalysts consisting of TiCl4 with trialkylaluminum as a co-catalyst and MgCl2 or Si02 as a support.8 The activity of these systems approach one million grams of polymer per one gram of TiCl4; however, these heterogeneous systems are not amenable to mechanistic study. When Sinn and Kaminsky found that metallocene dichlorides in the presence of methylalumoxane (MAO) resulted in an active polymerization catalyst, it provided the opportunity for studies with homogeneous systems.9 This result and the work of BreslowlO suggested that the role of the aluminum cocatalyst is to alkylate the transition metal to Cp2M(R)Cl (2) and then abstract a halogen to afford [Cp2MR] +, (3).11 This 14 electron species is presumed to be the active polymerization catalyst. Homogeneous group IV cationic metallocenes have been studied extensively as a model for the heterogeneous process.12 However, choosing 95 the proper counterion can be crucial to its successful isolation, as the P-F and C-H bonds of both [PF6]- and [B(C6Hs)4]- counterions are activated by these catalysts.13 Recently, it has been found that the tetrakisperfluorophenylborate anion, [B(C6Fs)4]-, is an inert non-coordinating counter-anion.14 This anion can be easily introduced by protonation of 4 with an anilinium salt15 or by methyl anion abstraction from 4 with the trityl salt16 or by the neutral B(C6Fs)3 to afford the related [CH3B(C6Fshl- anion. 17 (Scheme I) Both cations 5 and 6 have been found to be active ethylene and propylene polymerization catalysts. Scheme I [NEt3 H][B(C 6F5 ) 4 ] or [Ph3C][B(C6F5) 4] 5 4 6 For the last ten years, homogeneous catalysts of group III, lanthanide and group IV metals have been prepared as models of the heterogeneous polymerization systems. Early on, Watson demonstrated that a neutral lanthanide metallocene system performs many of the key reactions in olefin polymeriza tion.18 96 Scheme II 7 9 8 10 11 Exposure of the methyl complex (7) to excess propene afforded the isobutyl complex (8). Subsequent studies demonstrated that 8 undergoes ~-H elimination to 9, ~-CH3 elimination to 7, olefin insertion to 10, and cr bond metathesis of the Lu-R bond to 11, all of which serve as chain termination pathways. (Scheme II) Marks and Schumann have provided a method of preparing halidefree lanthanide polymerization ca tal ys ts.19 Trea trnent of [Li(etherh][Cp""2MCl2l (M =La, Nd, Lu) with the bulky bis-trimethylsilylmethyllithium resulted in the isolation of 12. This technique is now often used to obtain halide-free early transition metal catalysts. 97 -* ~H(SiMe3 ) 2 12a, M =La b, M =Nd c, M = Lu Hydrogenation of 12 affords the corresponding hydride complexes, which are active ethylene polymerization catalysts. Previous work by Bercaw20 on scandocene complexes and their derivatives show that the group III metallocenes are also amenable to the study of insertion chemistry. The scandocene alkyl complexes (13) readily polymerize ethylene and a detailed study on the propagation and termination steps has been carried out.21 polyethylene 13a, R = CH 3 b, R = CH2CH 3 c, R = CH2CH 2CH3 Due to the steric bulk of the Cp* rings, these formally 14 electron alkyl complexes (13) are monomeric and can be prepared free of solvent. However, the steric bulk also retards the insertion of a-olefins, as exposure of 13 to aolefins results in the exclusive isolation of scandium alkenyl complexes, due to a cr-bond metathesis pathway. In order to create more reactive species, the cyclopentadienyl rings w ere linked using a dimethylsilyl unit, resulting in more space at the metallocene wedge.22 98 14 15 The polymerization reactivity of both hydrides 14 and 15 exceeded that for the permethylscandocene complexes. The dimerization of a-olefins in a "head-to-tail" fashion and cyclization of a-w-dienes are both observed using these catalysts. In order to achieve a truly "living" Ziegler-Natta olefin polymerization system, the steric crowding around the metal was further reduced in order to decrease competing reactions. Therefore, the linked [(Cp*SiNR)Sc] complexes (16 and 17) were prepared.23 99 Complex 16 readily polymerizes a-olefins, requiring the loss of PMe3 to achieve the active 12 electron species.24 In addition, the molecular weight distribution of the oligomers at low conversion indicates that nearly all of the scandium centers are active sites. The propyl dimer (17) was found to be even more active toward a-olefins.25 Diverse chemistry has been exhibited by the metallocene systems with regard to insertion, polymerization, and C-H activation processes. In order to prepare complexes with different metal and charge distributions, dianionic ligands have been used to replace cyclopentadienyl groups. For example, the dicarbollide ligand, [C2B9H11]2-, has been complexed to group III, IV, and V metals. Jordan has prepared both zirconium and hafnium alkyl analogues . [C 2 B9H 11 ]2- : • ] 2./-1~ [~~·-z•l '·\ . [ . .,_._ ·- ... ·-· n 18M= Zr 19M= Hf (• = BH; + = CH) The complexes exhibit pentahapto dicarbollide coordination and display reaction chemistry similar to that of the bent metallocene systems. The electrophilic nature of 18 and 19 was demonstrated by their coordination of d onor ligands to form adducts 20 and 21. Insertion of 2-butyne into the methyl complex 18 resulted in 22 with a ~-CH3 agostic interaction, which further demonstrates the electrophilicity of the metal center. Polyethylene was produced when 18 was exposed to ethylene; 2-methyl-1-pentene and 2, 4dimethyl-1-heptene were isolated when 18 was exposed to propene. (Scheme III) 100 Scheme III ~..·v?\ ~._;\.7 .~-\. ~-·. 1~, · I~· ·&.. MeC=CMe ~~ / . . • • \ ~~ 1~,I· ·&.. THF ~~ / . . • • \ CH3 ~H n ~~~THF 22M= Zr 23M= Hf 3 18 M= Zr 19M= Hf 20M= Zr 21M= Hf + polyethylene Group five analogs can also be easily prepared by two methods. Treatment of Cp'TaCl4 (Cp' = 11S-CsH4Me) with one equivalent of the dilithium carbollide followed by alkylation with methylmagnesium bromide affords 24. Alternatively, treatment of TaCls with one equivalent of the dilithium carbollide followed by methylmagnesium bromide yields 25. The polymerization chemistry of these complexes has not been reported. 24 25 Previous work in the Bercaw group has demonstrated that the dicarbollide ligand is easily introduced to the [Cp*Sc] fragment. However, with the dicarbollide ligand, crystal structures of several complexes, including 26, have shown interactions between the B-H bond of one dicarbollide with l0 l the metal center of a second dicarbollide ligand.26 This B-H agostic interaction provides electron density to the electrophilic metal, thus reducing the activity of the complex.27 26 As mentioned earlier, group IV industrial catalyst are successfully modelled by neutral group III and group IV metallocenes. Ideally, however, the polymerization catalyst would not require counterions, would not possess ~-H agostic interactions, and would not dimerize. In order to achieve such a catalyst, complexes with the dianionic borollide, (C4H4BNiPrz)2-,28 have been prepared. The borollide ligand is expected to be similar to both the dicarbollide and the cyclopentadienyl analogues in its coordination to various transition metal centers.29 The neutral zirconium and hafnium borollide complexes would be isoelectronic to the neutral group III (13a) and cationic group IV (5) metallocene complexes. (Scheme IV). Therefore, zirconium borollide complexes were considered extremely likely to serve as Ziegler-Natta polymerization ca talys ts. 102 Scheme IV 0 13a .. 5 This chapter recounts the synthesis of the borollide complexes and their properties as polymerization catalysts. In addition, the amine nitrogen on the borollide permits study of the unique situation of an electrophilic center and a basic center that are in close proximity, yet not directly bonded to each other (Chapters 2 and 3) . This aspect will be explored in the potential of the borollide complexes in the heterolytic activation of H-X (X = Cl, OR, NHR, CR3) bonds. 103 Results and Discussion A zirconium compound with the borollide ligand was first prepared by treating Cp*ZrCb with Li2(C4H4BNiPr2)·THF. The reaction in toluene afforded a polymeric complex with LiCl, 28. This product is insoluble in benzene, but recrystallized from toluene/petroleum ether to afford pure 28 in 57% yield. When the reaction was carried out in diethyl ether, a burgundy monomeric complex with LiCl and diethyl ether (27) was isolated. (Scheme V) Scheme V Cp*ZrC13 + 27 n 28 Slow cooling of a concentrated solution of 27 in diethyl ether afforded crystals which were submitted for X-ray diffraction studies with the ORTEP diagram shown in figure 1. Inspection of the atom-atom bond distances around the borollide suggested that the zirconium center is 115-bonded to the borollide ligand (Figure 2). 104 105 Bond distances CA) Zr-C1 2.405 Zr-Cz 2.354 Zr-C3 2.439 Zr-C4 2.518 Zr-B 2.714 C1-C2 1.404 Cz-C3 1.377 C 3-C4 1.423 B-C1 1.526 B-C4 1.520 An~les ( } 0 C1-B-N C4-B-N C 1-B-C4 129.9 128.5 101.6 ~NR 2 \ Zr Figure 2. Hapticity of the zirconium borollide. Therefore, the ring does not have 114-character which is in sharp contrast to (C4~BNiPr2)zCr(CO)z (29) and (C4~BNiPr2)zMnCO (30). In both of these compounds, the borollide bonds in a fashion characteristic of a diene.30 29 30 Furthermore, in 27, the boron atom, the two adjacent carbon atoms to boron, and the nitrogen atom of the isopropyl group are coplanar. In the crystal structures of 29 and 30 a dative bond between the boron and nitrogen is suggested by the B-N distances of 1.42A and 1.40A, respectively. In 27 , the 106 B-N distance is 1.43A, which would apparently suggest a dative bond between the boron and nitrogen atoms. However, with an T)S-borollide, the planarity of the amine nitrogen can be accounted for by the localization of the lone pair in an orbital that is primarily p in character.31 As mentioned above, all of the zirconium borollide complexes are intensely colored. This result was intriguing since the expected dianionic nature of the borollide predicted do metal centers and therefore, preclude the intense colors observed. However, ligand-to-metal charge transfer events can explain the observed colors. In order to test this hypothesis, the UV-visible spectrum of 28 was taken in THF. Also, the electrochemical properties of 28 was determined in order to compare it to the charge transfer energy value calculated from the spectroscopic study. The UV-visible spectrum exhibited a peak at 570 nm. Using EcT =he / A.(N A) (where h is Planck's constant, A. is the wavelength of the peak, cis speed of light, and NA is Avogadro's number), the charge transfer energy is calculated to be 50 kcal / mole. The cyclic voltammogram exhibited an oxidative wave at -320 mV and a reductive wave at -2.12 V. Using E = -96.5X (where X is the difference in the oxidative and reductive wave potentials), the charge transfer energy is calculated to be 56 kcal / mole. These results are consistent with a LMCT event which is responsible for the intense colors observed for the complexes. Derivitization of 27 is readily accomplished with benzylpotassium, trimethylsilylmethyllithium and phenyllithium to afford 31, 32, and 33, respectively. MR diethyl ether n MR = LiCH 2TMS, LiPh, KCH 2Ph R = CH 2TMS (31) = Ph (32) = CH2Ph (33) 107 Interestingly, the 1H NMR spectra for these three complexes exhibit four borollide resonances, which indicates that in solution, the borollide ring rotates slowly or not at all on the NMR time scale. Treatment of 27 with smaller alkylating agents such as methyllithium resulted in a mixture of species, presumably mono- and dialkylated products. The behavior of Cp*(C4H4BNiPr2)ZrPh and Cp*(C4H4BNiPr2)ZrCH2Ph as Ziegler-Natta polymerization catalysts was examined. polyethylene R =Ph R = CH Ph 6.06 3.20 119,900 69,679 Cp*(C4H4BNiPr2)ZrPh catalyzes the polymerization of CH2=CH2, but the reaction is slow. On the other hand, Cp*(C4H4BNiPr2)ZrCH2Ph rapidly polymerized ethylene with the formation of a polymer apparent within minutes under conditions where Cp*(C4H4BNiPr2)ZrPh required 12 hours. This result was anticipated since the initiation of Cp*(C4H4BNiPr2)ZrPh requires breaking a relatively strong Zr-C(sp2) bond. With a weaker Zr-C(sp3) bond, initiation is more facile with Cp*(C4H4BNiPr2)ZrCH2Ph. Though Cp*(C4H4BNiPr2)ZrCH2Ph is an active ethylene polymerization catalyst, attempts to polymerize propylene met with little success. Small scale reactions in NMR tubes revealed that Cp*(C4H4BNiPr2)ZrCH2Ph underwent only several propylene insertions, affording small oligomers. Interestingly, CO did not insert into the Zr-C bond of Cp*(C4H4BNiPr2)ZrCH2TMS. These alkyl and aryl complexes are 14 electron species; therefore, they might be expected to coordinate a donor solvent or ligand. Interestingly, preparation of these complexes in diethyl ether resulted in donor-free products. These results indicate that the 14 electron species might dimerize in solution. However, a solution molecular weight determination showed that Cp*(C4H4BNiPr2)ZrCH2TMS is monomeric in a benzene solution. In an attempt to increase the reactivity of the borollide complexes, a cyclopentadienyl complex was prepared. This compound was predicted to 108 have less steric blockage in the wedge of the metallocene and, hence, be a better catalyst for a-olefin polymerization. Therefore, CpZrCl3(DME) was treated with one equivalent of Li2(C4H4BNiPr2)·THF to afford Cp(C4H4BNiPr2)ZrCl·LiCl(DME), 34, as a green solid. 34 Reaction of 34 with either bis-trimethylsilylmethyllithium or benzylpotassium resulted in an ill-defined mixture of products. This result was not unpredicted, since other complexes with dimethoxyethane or tetramethylethylenediamine as LiCl adducts are also unreactive.32 It is possible that alkylation of CpZrCl3(DME) prior to the introduction of the borollide ligand will result in a DME-free complex, Cp(C4H4BNiPr2)ZrCl·LiCl. In addition to the studies of Ziegler-Natta polymerization, the borollide complexes also provide a unique opportunity to study the ramifications of an electrophilic center in close proximity to a basic site. This situation sharply contrasts the complexes in the previous two chapters; in those complexes an electrophilic center is directly attached to a basic site (oxo or imido group). When 28 was treated with one equivalent of HCl, a yellow solid was isolated, and the number of resonances in the lH NMR spectrum suggests that the proton is hydrogen-bonded to both of the chloride atoms in the metallocene wedge.33,34 Complex 35 can be envisioned as the formal heteroly tic cleavage of the H-Cl bond by 28. The hafnium analogue has also been prepared and the symmetry of the lH NMR spectrum also suggested a complex isostructural to 35. 109 n 28 35 However, an X-ray diffraction study of the hafnium analogue showed that the amine hydrogen is not located between the two chlorine atoms. Instead there is hydrogen-bonding to only one of the chloride atoms.35 The reactions between 28 and other heterolytic cleavage substrates, including CpH,tert-butylacetylene, and CH30H were explored; however, no reaction occurred, suggesting that these C-H bonds are not sufficiently acidic to effect heterolytic cleavage. In a related reaction, 28 was treated with one equivalent of methyl iodide, and 36 was isolated as an orange solid. n 28 36 This type of chemistry is precedented by the reaction of (T)S-CsHsNMezhFe with two equivalents of CH3I to afford [(T)5-CsHsNMe3hFe]b.36 An example of an intramolecular proton transfer to the borollide ligand was found upon the treatment of 28 with lithium tert-butylamide in benzene to afford 37 as a tan product (Scheme VI). ll 0 Scheme VI n 28 37 THF11-THF 38 It is intriguing that the amino group is capable of abstracting the proton from the amide, but not from CpH (pKa- 15) or tBuC=CH (pKa - 25). Isolation of the zwitterionic complex 37 can be attributed to the formation of a strong zirconium imido bond upon proton transfer. This conjecture was substantiated by the appearance in the solid state IR spectrum of an absorbance at 1200 cm-1 for the Zr imido stretch. However, in the presence of coordinating solvents, the proton moves from the diisopropylamino group on the borollide to the zirconium imido group, which results in 38 (Scheme VI). These results are consistent with the earlier proposal that a ligand-tometal charge transfer is responsible for the intense colors of these compounds; the zwitterionic 37 would not be expected to contain a low energy ligand to metal charge transfer transition. In order to probe whether the proton transfer to the amino group is exclusive for the amido group, 11 1 Cp*(C4H4BNiPr2)ZrCH2TMS (31) was used to determine whether a markedly less acidic proton could be transferred to the diisopropylamino group. However, heating 31 in solution resulted only in its decomposition. The availability of 38 provided an opportunity to prepare the anionic imido species, [Cp*(C4~BNiPr2)Zr=NtBu]-, and study its reaction chemistry. However, deprotonation of 38 with alkyllithiums yielded only a mixture of products. When 38 was treated with lithium tert-butylamide, the bis-amido anion (39) was the product. 38 39 Similar reactivity was observed when 28 was treated with one and two equivalents of lithium anilide to yield 40 and 41, respectively. 40 41 Conclusion The borollide ligand, [C4H4BNiPr2]2-, provides a unique opportunity to prepare neutral group IV Ziegler-Natta polymerization catalysts. Though the alkyl complexes are 14 electron species, there is no indication that the borollide amine unit is capable of acting as a two electron donor to the electrophilic metal center. In fact, the crystal structure of 112 Cp*(C4H4BNiPr2)ZrCl·LiCl(Et20h shows that the nitrogen is not a donor and that the borollide is 115-coordinated to the zirconium center. The zirconium alkyl and aryl complexes are ethylene polymerization catalysts, but they catalyze only the oligomerization of a-olefins. Furthermore, the borollide ligand, with a basic group, exhibited interesting cleavage chemistry. When exposed to HCl, CH3I, and LiNHtBu, Cp*(C4~BNiPr2)ZrCl·LiCl affords Cp*(C4H4BNHiPr2)ZrCl2 and Cp*(C4~BN(CH3I)iPr2)ZrCl(I) and Cp*(C4H4BNHiPr2)Zr(=NtBu). In conclusion, the dianionic borollide ligand, (C4H4BNiPr2)2-, has provided a unique opportunity to study new metal / charge combinations in Ziegler-Natta polymerization chemistry. In addition, initial studies indicate that this basic ligand allows for interesting reaction chemistry, the full scope of which is just beginning to be surveyed. 113 Experimental General Considerations. All manipulations were performed using glovebox or high vacuum line techniques.37 Solvents were dried over LiAlH4 or Na/benzophenone and stored under vacuum over "titanocene:·38 Benzene-d6 and tetrahydrofuran-ds, were dried over activated molecular sieves (4A, Linde) and stored over "titanocene" or Na / benzophenone. Argon and nitrogen gases were passed over MnO on vermiculite and activated sieves. CpZrCl3(DME),39 Li2(C4B4BNiPr2)·THF,28 were prepared as previously described. Many reactions were monitored by NMR spectroscopy. Any experiment described in this chapter but not explicitly listed below was carried out in a sealed NMR tube using -0.7 mL of the NMR solvent with the appropriate reagents. Cp*(C4H4BNiPr2)ZrCl·LiCl (28). A 100 mL round bottom flask was charged with 2.50 g (7.51 mmol) Cp*ZrCl3 and 1.87 g (7.51 mmol) Li2(C4H4BNiPr2)·THF. A swivel frit assembly was attached to the reaction vessel. Approximately 60 mL toluene was then condensed onto the solids at -78°C. Even at -780C, the reaction commenced and the resultant purple solution was stirred for 24 hours. The LiCl precipitate was removed by filtration and the volatiles were removed in vacuo . Petroleum ether (20 mL) was then condensed on the solid at -780C. After warming to room temperature all of the solid dissolved. The solution was slowly cooled to -780C and filtration afforded a purple product (2.01 g, 4.28 mmol). Yield =57%. Analysis : Calculated (Found) C: 56.53 (53.15); H : 7.83 (7.17); N: 3.30 (2.71). Cp*(C4H4BNiPr2)ZrCH2TMS (31). A 50 mL round bottom flask was charged with 943 mg (2.02 mmol) Cp*(C4H4BNiPr2)ZrCl·LiCl and 209 mg (2.22 mmol) trimethylsilylmethyllithium. A swivel frit assembly was then attached. Approximately 25 mL toluene was condensed on the solids at -78°C, resulting in a red solution. The resultant solution was allowed to warm slowly to room temperature and was stirred overnight. LiCl was removd by filtration and the volatiles were removed in vacuo. The solid was washed with petroluem ether to yield 900 mg (1.89 mmol) of a red-brown product. Yield = 93%. Analysis: Calculated (Found) C: 60.47 (59.29); H: 9.30 (8.91); N : 2.94 (2.32). 1 14 Cp*(C4H4BNiPr2)ZrPh (32). A 100 mL round bottom flask was charged with 1.01 g (2.16 mmol) Cp*(C4H4BNiPr2)ZrCl·LiCl and 200 mg (2.38 mmol) phenyllithium. A swivel frit assembly was then attached. Approximately 50 mL toluene was condensed on the solids at -78°C, and the resultant solution was allowed to warm slowly to room temperature. The solution was stirred overnight and then filtered to remove LiCl. The volatiles were removed in vacuo, and then 20 mL diethyl ether was condensed on the solid. Concentration, cooling, and filtration of the solution afforded 552 mg (1.18 mmol) of a red-brown solid. Yield =55%. Analysis : Calculated (Found) C: 66.92 (62.34); H : 8.21 (7.78); N: 3.00 (2.19). Cp*(C4H4BNiPr2)ZrCH2Ph (33). A 50 mL round bottom flask was charged with 670 mg (1.43 mmol) Cp*(C4H4BNiPr2)ZrCl·LiCl and 206 mg (1.58 mmol) benzyl potassium. A swivel frit assembly was then attached. Approximately 25 mL diethyl ether was then condensed onto the solids at -78°C. The resultant solution was allowed to warm to room temperature slowly and then stirred for 30 minutes. Precipitated LiCl was then removed by filtration and the volatiles were removed in vacuo to afford a fluffy orange solid. The residue was washed with petroleum ether and 587 mg (1.22 mmol) of an orange-red solid was isolated. Yield= 85%. Analysis : Calculated (Found) C : 67.47 (62.89); H: 8.39 (7.88); N : 2.91 (2.22). Cp(C4H4BNiPr2)ZrCl·LiCHDME) (34). A 100 mL round bottom flask was charged with 1.12 g (3.19 mmol) CpZrCl3(DME) and 800 mg (3.19 mmol) Lb(C4H4BNiPr2)·THF. A swivel frit assembly was then attached. Approximately 50 mL of THF was condensed on the solids at -78°C, and the solution was allowed to warm slowly to room temperature and then stirred overnight. The volatiles were removed in vacuo and 15 mL diethyl ether was then condensed on the solid. The LiCl was then filtered away and the volatiles were removed again in vacuo. The residue was washed with petroleum ether to afford 1.06 g (2.17 mmol) of a green product. Yield = 68%. Analysis : Calculated (Found) C: 46.81 (46.97); H: 6.82 (6.72); N : 2.86 (2.83). Cp*(C4H4BNHiPr2)ZrCl2 (35). A 50 mL round bottom flask was charged with 427 mg (1.00 mmol) Cp*(C4H4BNiPr2)ZrCl·LiCl. A swivel frit assembly was attached. Approximately 25 mL toluene was then condensed on the solid at 115 -78°C. One equivalent HCl was added using a gas bulb and the resultant solution was stirred for 9 hours . The volatiles were removed in vacuo, leaving a yellow residue which was extracted with diethyl ether to afford a yellow solution. The ether was removed in vacuo to yield a yellow solid (130 mg, 0.28 mmol) . Yield = 28%. Analysis : Calculated (Found) C: 47.68 (52.06); H: 6.60 (7.43); N : 2.78 (3.03). IR spectroscoy (KBr, cm-1 ): 3424.2, 2972.7, 2905.7, 1389.3, 1375.7, 1317.3, 1256.1, 806.9. Cp*(C4H4BN(CH3)iPr2)Zri(Cl) (36). A 50 mL round bottom flask was charged with 500 mg (1.07 mmol) Cp*(C4H4BNiPr2)ZrCl·LiCl. A swivel frit assembly was then attached. Approximately 25 mL toluene was condensed on the solid at -78°C, and then 1 equivalent CH3I was added using a gas bulb. The purple solution was stirred for one hour. A small amount of THF (5 mL) was then added at -78°C and the solution was allowed to warm to room temperature. The resultant orange solution was stirred overnight, and the volatiles were then removed in vacuo. Toluene was condensed on the solid, and the orange solution was filtered. The volatiles were removed in vacuo, resulting in an orange solid (179 mg, 0.03 mmol). Yield = 30%. Analysis : Calculated (Found) C: 44.49 (40.30); H: 6.41 (5.56); N : 2.47 (1.95). Cp*(C4H4BNiPr2)ZrNHtBu (38). A 100 mL round bottom flask was charged with 1.0 g (2.14 mmol) Cp*(C4H4BNiPr2)ZrCl·LiCl and 160 mg (2.05 mmol) lithium tert-butylamide. Attached swivel frit assembly. Approximately 50 mL benzene was condensed on the solids at -78°C. The solution was stirred overnight at room temperature. Then the volatiles were removed in vacuo and diethyl ether was condensed in the flask. A white solid (LiCl) was filtered . Removed the volatiles to afford 710 mg (1.54 mmol) of a tan solid. Yield= 72 %. X-Ray Crystal Structure Determination of Cp*(C4H4BNiPr2)ZrCl·LiCHOEt2h· The ORTEP drawing of Cp*(C4H4BNiPr2)ZrCl·LiCl(OEt2h is shown in figure 1. To obtain the structure a burgundy plate, which was obtained by cooling a diethyl ether solution of the complex, was mounted in a greased capillary. The crystal was then centered on a CAD-4 diffractometer. Unit cell parameters and an orientation matrix were obtained by a least squares calculation from the setting angles of 25 reflections with 16° < 9 < 18°. 11 6 Coordinates of the zirconium atom were obtained from a Patterson map; locations of the other non-hydrogen atoms were determined from successive structure factor-Fourier calculations. Calculations were done with programs of the CRYM Crystallographic Computing System and ORTEP with scattering factors and corrections for anamalous scattering taken from a standard reference.40 1 17 Table I. lH NMR Spectral Data (Bo = (C4H4BNiPr2)) for comp exes 28- 38 Compound Cp*BoZrCl·LiCl (28) in THF-da Assignment 8 in ppm (m) N-CH-(CH3h Cs(CH3)5 N-CH-CH3 1.07 (d) J (Hz) 6.7 1.86 (s) CH2CH2B CH2CH2B 3.47 (p) 3.70 (t) 5.21 (t) 6.9 3.9 3.6 N-CH-(CH3h 1.31 (d) 6.7 Cs(CH3)5 1.99 (s) N-CH-CH3 CH2CH2B 3.74 (m) 4.48 (t) 6.7 3.7 CH2CH2B 5.77 (t) 3.8 Cp*BoZrCH2TMS (31) CH2Si(CH3)3 in C6D6 CH2Si(CH3)3 CH2Si(CH3)3 -0.70 (br) -0.32 (br) Cp*BoZrCl·LiCl (28) in C6D6ITHF-da N-CH-(CH3h Cp*BoZrPh (32) in THF-da 0.41 (s) 1.42 (br) 1.95 (s) Cs(CH3)5 N-CH-(CH3h 3.59 (m) CH2CH2B 4.18 (br) CH2CH2B 5.13 (br) CH2CH2B 5.57 (br) CH2CH2B 6.39 (br) N-CH-(CH3h 1.06 (d) Cs(CH3)5 1.68 (s) CH2CH2B 3.33 (d oft) 6.6 3J = 4.5 4J = 2.1 N-CH-(CH3h CH2CH2B 3.46 (sept) 3.70 (d oft) 6.6 3J = 5.1 4J = 2.4 CH2CH2B CH2CH2B 4.40 (m) para-C6Hs meta-C6Hs 6.58 (t) 7.2 6.71 (t) 7.43 (d) 7.2 ortho-C6Hs 5.84 (m) 6.3 118 T a ble I . (C ontmued) lH NMR S,pectra1 D ata f or comp.1exes 28 - 38 Cp*BoZrCH2Ph (33) in THF-ds CH2Ph N-CH-(CH3)2 CH2Ph Cs(CH3)5 CH2CH2B 1.85 (s) 3.10(doft) CH2CH2B 3.28 (d oft) N-CH-(CH3)2 CH2CH2B CpBoZrCl·LiCl(DME) (34) in C6D6 0.89 (d) 1.02 (d) 1.58 (d) 3.33 (sept) 4.38 (m) CH2CH2B aromatic 5.21 (m) N-CH-(CH3)2 1.40 (br) CH2-0-CH3 2.62 (s) CH2-0-CH3 2.94 (s) N-CH-CH3 3.83 (br) 4.45 (br) CH2CH2B 9.3 6.6 9.3 4J = 4.8 3J = 2.4 4J = 4.5 3J = 2.4 6.9 6.30-6.90 CsHs CH2CH2B 6.47 (s) Cp*BoZrCl·HCl (35) N-CH-(CH3)2 0.86 (d) in C6D6 N-CH-(CH3)2 Cs(CH3)5 N-CH-CH3 0.89 (d) 1.99 (s) 3.19 (m) CH2CH2B 4.78 (t) CH2CH2B NH-CH-(CH3h 5.92 (t) 6.55 (br) 6.43 (s) 6.6 6.9 6.9 4.2 3.6 119 T a bl e I . (C on1nue f d) 1 H NMR S,pee tr a1 Da t a f or cornp. exes 28 - 38 Cp*BoZrCl(CH3I) (36) N-CH-(CH3)2 1.17 (rn) in THF-ds N-CH3 Cs(CH3)5 N-CH-CH3 N-CH-CH3 2.07 (s) 2.02 (s) CH2CH2B CH2CH2B CH2CH2B CH2CH2B Cp*BoZrNHtBu (38) in C6D6/ THF-ds N-CH-(CH3h N-C(CH3)3 Cs(CH3)5 N-CH-CH3 CH2CH2B N-H CH2CH2B CH2CH2B CH2CH2B 3.23 (sept) 3.35 (sept) 3.90 (br) 4.83 (br) 5.71 (br) 6.26 (br) 1.22 (d) 1.32 (s) 2.00 (s) 3.34 (br) 4.17 (br) 4.63 (s) 4.79 (br) 5.51 (br) 6.52 (br) 6.6 6.6 120 Tabl e II 13C NMR S,pectra1 D at a (B 0= (C 4 ~BNiPf2 )) f or comp. exes 28 - 38 Assignment 8 (ppm) Cp*BoZrCl·LiCl (28) Cs(CH3)5 12.27 in C6D6 I THF-ds N-CH-CH3 N-CH-CH3 24.00 Compound CH2-CH2-B Cs(CH3)5 CH2-CH2-B Cp*BoZrCH2TMS (31) in C6D6 CH2-Si-( CH3)3 CH2-Si -(CH3)3 Cs(CH3)5 N-CH-CH3 N-CH-CH3 CH2-CH2-B CH2-CH2-B CH2-CH2-B CH2-CH2-B Cs(CH3)5 Cp*BoZrPh (32) in THF-ds 47.31 97.71 119.65 124.51 4.74 12.30 12.44 24.16 47.50 93.20 96.74 109.40 112.99 119.00 9.67 Cs(CH3)s N-CH-CH3 21.41 N-CH-CH3 44.82 CH2-CH2-B 85.06 CH2-CH2-B 92.40 CH2-C6Hs CH2-C6Hs Cs(CH3)5 104.71 CH2-C6Hs CH2-CH2-B CH2-CH2-B CH2-C6Hs 112.92 118.99 122.24 123.55 137.15 195.06 121 Table II (Contmued) 13C NMR spectra for cornp exes 28- 38 Cp*BoZrCH2Ph (33) in THF-ds Cs(CH3)5 N-CH-CH3 N-CH-CH3 CH2-Ph CH2-CH2-B CH2-CH2-B CH2-C6Hs CH2-C6Hs CpBoZrCl·LiCl(DME) (34) in C6D6 Cp*BoZrCl·HCl (35) in C6D6 9.56 21.50 44.77 50.28 86.03 90.53 106.90 112.78 CH2-C6Hs Cs(CH3)5 CH2-CH2-B 114.99 119.15 CH2-CH2-B CH2-C6Hs 125.01 155.40 N-CH-CH3 N-CH-CH3 23.96 47.69 CH2-0-CH3 59.11 CH2-0-CH3 70.05 CH2-CH2-B 93.76 CsHs CH2-CH2-B 113.78 Cs(CH3)5 N-CH-CH3 12.28 N-CH-CH3 N-CH-CH3 CH2-CH2-B Cs(CH3)5 CH2-CH2-B 123.95 126.39 20.16 20.54 51 .01 104.66 116.54 121.09 122 Ta bl e II (C ontmued) 13C NMR spectra f or cornp. exes 2 8 - 38 Cp*BoZrCl(CH3I) (36) in THF-ds Cs(CH3)5 N(CH3)CH(CH3h N-CH-CH3 N-CH-CH3 N-CH-CH3 N-CH-CH3 N-CH-CH3 N-CH-CH3 12.62 17.89 N-CH-CH3 45.38 N-CH-CH3 53.78 CH2-CH2-B CH2-CH2-B 94.02 21.50 22.24 22.67 23.20 23.57 24.08 119.48 Cs(CH3)5 CH2-CH2-B 124.01 CH2-CH2-B 140.27 131.28 123 References 1. 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Jr. Ziegler-Natta Catalysts and Polymerizations. Academic Press, London, 1979. (b) Tait, P. J. T. Comprehensive Polymer Science Pergamon Press, 124 Oxford, 1989. 12. (a) Jordan R. F. Advances in Organometallic Chemistry 1991, 32 , 325. (b) Bochmann reference (c) Teuben reference 13. (a) Jordan, R. F.; Dasher, W. E.; Echols, S. F. f. Am. Chern . Soc . 1986, 108 , 1718. (b) Hlatky, G. G .; Turner, H. W.; Eckman, R. R. f . Am. Chern . Soc. 1989, 111 , 2728. 14. Strauss, S. H . Chern . Rev. 1993, 93 , 927. 15. (a) Hlatky, G. G .; Turner, H. W.; Eckman, R. R. f. Am. Chern . Soc. 1989, 111, 2728. (b) Turner, H . W . European Patent Application 1988 2 77 004. (c) Hlatky, G. G .; Turner, H. W . European Patent Application 1988 2 77 003. 16. Chien, J. C. W .; Tsai, W-M.; Raush, M. D. f. Am . Chern . Soc. 1991, 113 , 8570. 17. Xinmin, Y.; Stern, C. L.; Marks, T. J. f. Am. Chern . Soc. 1991, 113 , 3623. 18. (a) Watson, P. L. f. Am . Chern. Soc . 1982, 104, 337. (b) Watson, P. L.; Roe, D. C. ]. Am . Chern . Soc . 1982, 104, 6471. 19. Jeske, G.; Lauke, H .; Mauermann, H .; Swepston, P. N.; Schumann, H .; Marks, T. J. f. Am. Chern. Soc. 1985, 107, 8091. 20. Thompson, M . E.; Baxter, S. M.; Bulls, A . R.; Burger, B. J.; Nolan, M. C.; Santarsiero, B. D.; Schaefer, W . P.; Bercaw, J. E. f. Am . Chern . Soc. 1987, 109, 203. 21. Burger, B. J.; Thompson, M . E.; Cotter, W . D.; Bercaw, J. E. f. Am . Chern . Soc . 1990, 112, 1566. 22. (a) Piers, W. E.; Shapiro, P. J.; Bunel, E. E.; Bercaw, J. E. Synlett 1990, 2, 74. (b) Bunel, E. E. Ph. D. theis, California Institute of Technology, 1989. 23. Shapiro, P. J.; Bunel, E.; Schaefer, W. P.; Bercaw, J. E. Organometallics 1990, 9, 867. 24. Shapiro, P. J.; Cotter, W. D.; Bercaw, J. E. Manuscript in preparation. 125 25. Shapiro, P. J. Ph. D. Thesis, California Institute of Technology, 1990. 26. Behnken, P. E.; Marder, T. B.; Baker, R. T.; Knober, C. B.; Thompson, M . R.; Hawthorne, M . F. f. Am. Chern . Soc . 1985, 107, 932. 27. Brookhart, M .; Green, M . L. H.; Wong, L.-L. Prog. Inorg. Chern . 1988,36, 1. 28. (a) Berberich, G. E.; Boveleth, W .; HePner, B.; Hostalek, M .; Koffer, D. P . J.; Ohst, H .; Sohnen, D. Chern. Ber. 1986, 119, 420. (b) Berberich, G. E.; Ohst, H. z. Naturforsch 1983, 838 , 1388. 29. (a) Berberich, G. E.; Negele, M.; Ohst, H. Chern. Ber. 1991, 124, 25. (b) Berberich, G. E.; Hessner, B.; Ohst, H.; Raap, I. A. f. Organomet. Chern. 1988, 348, 305. 30. Berberich, G. E.; Hessner, B.; Ohst, H . f. Orga nomet. Chern . 1988, 348, 305. 31. Kiely, A . F.; Bercaw, J. E. Unpublished results. Cp*(C4H4BNHiPr2)HfCl2 exhibits a B-N bond distance of 1.58 A in which there is no dative interaction between the boron and the nitrogen. 32. Coughlin, E. B. Ph. D. Thesis, California Institute of Technology, 1994. 33. Berberich, G. E.; Negele, M .; Ohst, H . Chern. Ber. 1991, 124, 25. 34. A variable temperature NMR study showed no changes in the spectra from that obtained at room temperature. 35. Kiely, A. F.; Bercaw, J. E. Unpublished results. 36. Stahl, K-P.; Boche, G.; Massa, W. f. Organomet. Chern. 1984, 277, 113. It was found that (TJS-CsH4NMe2hFe reacts with two equivalents of CH3I to afford [(TJ5-Cs~Me3)2Fe]l2 . 37. Burger, B.J.; Bercaw, J. E. In Experimental Organometallic Chemistry ; Wayda, A. L., Darensbourg, M. Y. Eds.; ACS Symposium Series 357; American Chemical Society, Washington, D. C. 1987. 38. Marvich, R. H .; Brintzinger, H. H. f. Am. Chern. Soc. 1971, 93, 2046. 126 39. Lund, E. C.; Livinghouse, T. Organometallics 1990, 9, 2426. 40. International Tables for X-ray Crystallography, Volume IV, p . 71, p . 147; Birmingham, Kynoch Press, 1974. 127 Appendix 3. X-ray crystal structure data for Cp*(C4f4BNiPr2)ZrCl·LiCl(Et20h (27). Table III. Crystal and Intensity Collection Data for Cp*(C4f4BNiPr2)ZrCl·LiCl(Et20h (27). chemical formula crystal dimension, mm crystal system space group C2sHs3BCl2N02ZrLi a,A 11.013 (5) b,A 21.440 (11) c,A 14.462 (5) ~,deg 95.91 (3) V, A3 3396.6 (26) Peale, g cm-3 1.20 z 4 A.,A ~' cm-1 temp, oc 28 rang, deg no. of reflections measured, total R 0.711 GOF 0.11 X 0.30 X 1.15 monoclinic P21 / n 4.98 23 2-42 7997 0.036 2.44 128 Table IV. Final Heavy Atom Parameters for Cp*(C4fi4BNiPrz)ZrCl·LiCl(Et20)2 (27). :z:,y,z and Ueq 0 Atom X 10 4 :z: y z Ueq or Zr 2170(.7) 2008(.3) 4209( .4) 533(2) Cl1 672(2) 2046(1) 2760(1) 637(5) Cl2 1212(2) 958(1) 4571(1) 686(6) Cp1 4481(7) 2048(5) 4480(6) 674(25) Cp2 4172(8) 2310( 4) 3607(7) 746(28) Cp3 3687(7) 1841(5) 3013(5) 706(27) Cp4 3654(7) 1298( 4) 3518(7) 740(27) CpS 4157(7) 1423( 4) 4437(6) 646(25) Cp6 5267(9) 2364(5) 5283(7) 1327(38) Cp7 4521(9) 2948(5) 3305(8) 1394(39) CpS 3365(9) 1913(6) 1972(6) 1513(47) Cp9 3318(9) 648(5) 3155(7) 1384(39) Cp10 4355(8) 945(5) 5202(7) 1144(33) C1 2313(7) 3022(4) 4924(5) 665(23) C2 2481(9) 2563(5) 5618(6) 878(33) C3 1397(11) 2255(4) 5687(6) 862(34) C4 466(7) 2478( 4) 5013(5) 667(23) B 956(8) 3063( 4) 4589(5) 544(25) N 308(6) 3512(3) 3991( 4) 599(19) cs -1002(10) 3498( 4) 3810(7) 1003(34) B 129 Table IV. (Continued) C6 -1551(9) 3341(5) 2886(7) 1392(41) C7 -1699(9) 3871(5) 4417(6) 1243(36) C8 876(11) 4046( 4) 3621(7) 1103( 40) C9 1301(9) 4540( 4) 4244(7) 1201(35) C10 1500(10) 3920(5) 2802(8) 1289(39) Li -258(12) 1107(6) 3240(9) 737(40) 01 -1956(5) 1212(3) 3426( 4) 1191(23) Cll -2729(12) 1520(6) 2645(9) 11.7(3) • C12 -3458(12) 1070(6) 2120(9) 13.8( 4) • C13 -2589(16) 1095(8) 4145(14) 19.3(6) • C14 -2060(13) 934(6) 4978(10) 14.7(4) • 02 -182(6) 436(3) 2306(5) 1179(23) C15 -394(19) 604(9) 1282(15) 20.5(8) • C16 361(17) 724(8) 897(12) 18.1(6) • C17 -84(22) -197(12) 2488(15) 24.6(9) • Cl8 -622(17) -404(8) 3015(13) 18.8(6) • Cl Ucq = l Li L;[Ui;(a;a;)(cii . a;)] • Isotropic displacement parameter, B 130 Table V. Anisotropic Displacement Parameters for Cp*(C4I-4BNiPr2)ZrCl·LiCl(Et20h (27). Atom Uu U22 u33 ul2 u13 Zr Cl1 Cl2 Cp1 Cp2 Cp3 Cp4 606( 5) 689(13) 669(15) 533(51) 594(61) 540(56) 643(61) 574(5) 706(13) 711(14) 689(64) 643(61) 1012(81) 729(67) 417( 4) 501(11) 680(14) 774( 63) 1017(77) 574(57) 880(72) CpS Cp6 Cp7 Cp8 628(58) 945(79) 987(78) 656(62) 1600(94) 1039(78) 657(63) 1330(89) 2216(117) 42(5) 17(13) 21(12) 70(53) -69(50) -14(54) -125(51) 162(49) 130(69) 141(74) 46(3) -8(10) 81(11) -64( 44) 166(56) 92( 45) 230(55) 87( 48) -399 (69) 455 (79) 949(75) 1005(82) 855(72) 800(62) 1040(87) 3052(146) 1312(89) 1309(82) 660(52) 1044(79) 900(75) 562(58) 1921(108) 1267(82) 518(48) 519(62) -47(93) -257(68) 351(64) 105(54) 436(68) 376(52) 592(53) 433(50) 639( 43) 820(71) 1176(88) 1038(78) 839(75) 1479(91) 1507(103) 870(100) 1068(51) 1326(59) 432(69) 146(50) 116(61) 42(38) 404(69) -62(78) 171(75) -111(72) -216(66) 192(54) 560(78) 107(64) -12(43) -62(62) 308(63) 202(50) 37( 49) -40(38) -90(63) -73(74) 153(65) 165(75) 335(75) -194(73) 18(76) -180( 44) -148(42) 406(82) -13(82) 134( 41) -150( 46) Cp9 Cp10 C1 C2 C3 C4 B N cs C6 C7 C8 C9 C10 Li 01 02 1357(98) 756(63) 701(69) 672(51) 869(81) 1078(89) 952(77) 1929(117) 1306(91) 1323(97) 664(98) 791(47) 1215(56) 680(58) 495(62) 465( 42) 1283(87) 1883(113) 1749(102) 547(63) 857(71) 1090(85) 659(92) 1721(64) 937( 49) U23 -6(5) 58(11 ) 166(11 ) -169(58 ) 1 78(62 ) 44(58 ) -393( 59 ) 59 ( 50) -720( 73 ) 414(85 ) 167( 83 ) -1024(80) 427(68 ) -89( 47) -166(56 ) 94(46 ) - 78( 45 ) -105( 52 ) -5(34 ) -150(62 ) -587(77) -343(72) -142(58 ) -417(68 ) -49( 74) -49( 78) 459( 4 7) 243( 43 ) Ui ,i values have been multiplied by to• The form of the displacement factor is: 2 2 exp -21r 2 (U11 h 2 a•, + U22 k 2 b• + U33 l 2 c• + 2U12hka•b• + 2U13hla•c• + 2U23klb"c" ) 131 Table VI. Complete Distances and Angles for Cp•(C4!-4BNiPr2)ZrCHJCl(Et20h (27). Distance( A) 2.531{2) 2.563(2) 2.236 2.535(8) 2.536(9) 2.550(9) 2.515(9) 2.514(8) 2.165 2.405(8) 2.354(10) -C3 2.439(10) -C4 2.518(8) -B 2.714(9) Li -Cll 2.393(13) Li -Cl2 2.405(13) Li -01 1.930(14) Li -02 1.982(15) Cp1 -Cp2 1.390(12) Cp1 -CpS 1.387(12) Cp1 -Cp6 1.533(13) Cp2 -Cp3 1.393(13) Cp2 -Cp7 1.497(14) Cp3 -Cp4 1.376(12) Cp3 -CpS l.S20(13) Cp4 -CpS 1.412(12) Cp4 -Cp9 1.520(13) CpS -Cp10 1.50S(13) C1 -C2 1.404(12) C1 -B 1.526(12) C2 -C3 1.377(14) C3 -C4 1.423(12) C4 -B 1.520(12) B -N 1.433(11) N -C5 1.440(11) Zr Zr Zr Zr Zr Zr Zr Zr Zr Zr Zr Zr Zr Zr -Cl1 -Cl2 -Cp -Cp1 -Cp2 -Cp3 -Cp4 -CpS -Cb -C1 -C2 Distance( A) N -C8 1.434(12) cs -C6 1.448(14) C5 -C7 1.463(14) C8 -C9 1.437(14) CB -C10 1.454(14) 01 -Cll 1.496(14) 01 -C13 1.334(19) en -C12 1.423(18) C13 -C14 1.33(2) 02 -C15 1.52(2) 02 -C17 1.38(3) C15 -C16 1.08(3) C17 -C18 1.10(3) Cp6 -Hp1A 0.946 Cp6 -Hp1B 0 .955 Cp6 -Hp1C 0.948 Cp7 -Hp2A 0.956 Cp7 -Hp2B 0 .945 Cp7 -Hp2C 0 .944 Cp8 -Hp3A 0.954 CpS -Hp3B 0 .947 CpS -Hp3C 0.947 Cp9 -Hp4A 0.932 Cp9 -Hp4B 0.951 Cp9 -Hp4C 0.959 Cp10 -Hp5A 0.948 Cp10 -Hp5B 0.949 Cp10 -Hp5C 0.954 C1 -H1 0.952 C2 -H2 0.952 C3 -H3 0.953 C4 -H4 0.954 cs -H5 0 .955 C6 -H6A 0.949 C6 -H6B 0.949 132 Table VI. (Continued) C6 C7 C7 C7 -H6C -H7A -H7B -H7C cs -HS C9 -H9A C9 -H9B C9 -H9C C10 -H10A C10 -H10B C10 -HlOC Cll -HllA Cll -HllB Cl2 -Hl2A Cl2 -Hl2B Cl2 -Hl2C Cl3 -Hl3A Cl3 -Hl3B C14 -Hl4A Cl4 -Hl4B Cl4 -H14C C1S -HlSA ClS -H1SB ClS -Hl6B C16 -Hl6A C16 -H16B Cl6 -H16C Cl7 -Hl7A Cl7-Hl7B C18 -H18A Cl8 -Hl8B C18 -H18C 0.937 0.94S 0.940 0.9SO 0.9S4 0.9SO 0.941 0.9S1 0.937 0.9S4 0.942 0.949 0.947 0.949 0.942 0.942 0.97S 0.920 0.947 0.970 0.916 0.997 0.920 l.S98 0.969 0.9S4 0.888 1.007 0.911 0.9SS 0.973 0.883 Cll -Zr -Cl2 Cp -Zr -Cb Cp -Zr -Cl1 Cp -Zr -Cl2 Cb -Zr -Cl1 Cb -Zr -Cl2 Cl1 -Li -Cl2 Cll -Li -01 Cll -Li -02 Cl2 -Li -01 Cl2 -Li -02 01 -Li -02 Zr -Cll -Li Zr -Cl2 -Li CpS -Cp1 -Cp2 Cp6 -Cp1 -Cp2 Cp6 -Cpl -CpS Cp3 -Cp2 -Cp1 Cp7 -Cp2 -Cpl Cp7 -Cp2 -Cp3 Cp4 -Cp3 -Cp2 CpS -Cp3 -Cp2 CpS -Cp3 -Cp4 CpS -Cp4 -Cp3 Cp9 -Cp4 -Cp3 Cp9 -Cp4 -CpS Cp4 -CpS -Cpl Cp10 -CpS -Cpl CplO -CpS -Cp4 B -C1 -C2 C3 -C2 -Cl C4 -C3 -C2 B -C4 -C3 C4 -B -Cl -B N -Cl 87.1(1) 132.7 109.3 10S.8 106.2 106.3 94.1(5) 113.1(6) 111.3(6) 119.1(6) 112.1(6) 106.8(7) 89.7(3) 88. 7(3) 108.2(8) 12S.2(8) 12S. 7(8) 108.1(8) 12S.9(8) 12S.0(8) 108.3(8) 12S.0(8) 126.S(8) 108.0(8) 127.6(8) 123.9(8) 107.S(7) 127.4(8) 12S.1(8) 108. 7(7) 109.7(8) 111.0(8) 107.0(7) 101.6(7) 129.9(7) 133 Table VI. (Continued) N -B -C4 -B -B C5 -N C8 -N C8 -N -cs C6 -cs -N C7 -cs -N C7 -cs -C6 C9 -CS -N C10 -C8 -N C10 -CS -C9 C13 -01 -C11 C12 -C11 -01 C14 -C13 -01 C17 -02 -C15 C16 -C15 -02 · C1S -C17 -02 Hp1A -Cp6 -Cp1 Hp1B -Cp6 -Cp1 Hp1C -Cp6 -Cpl HplB -Cp6 -Hp1A HplC -Cp6 -Hp1A Hp1C -Cp6 -Hp1B Hp2A -Cp7 -Cp2 Hp2B -Cp7 -Cp2 Hp2C -Cp7 -Cp2 Hp2B -Cp7 -Hp2A Hp2C -Cp7 -Hp2A Hp2C -Cp7 -Hp2B Hp3A -CpS -Cp3 Hp3B -CpS -Cp3 Hp3C -CpS -Cp3 Hp3B -CpS -Hp3A Hp3C -CpS -Hp3A Hp3C -CpS -Hp3B Hp4A -Cp9 -Cp4 128.5(7) 121.6(7) 123.5(7) 114.6(7) 119.2(8) 117.2(8) 119.1(9) 118.7(8) 114.6(8) 119.S(9) 111.7(10) 110.4(10) 122.7(15) 114.S(13) 120.7(19) 119.1(22) 10S.S 10S.3 10S.7 110.2 110.7 110.1 10S.O 10S.4 10S.7 110.1 110.3 111.2 10S.4 108.6 10S.7 110.2 110.1 110.8 109.0 Hp4B -Cp9 -Cp4 Hp4C -Cp9 -Cp4 Hp4B -Cp9 -Hp4A Hp4C -Cp9 -Hp4A Hp4C -Cp9 -Hp4B HpSA -Cp10 -CpS HpSB -Cp10 -CpS HpSC -Cp10 -CpS HpSB -Cp10 -HpSA HpSC -Cp10 -Hp5A Hp5C -Cp10 -Hp5B H1 -Cl -C2 H1 -C1 -B H2 -C2 -C1 H2 -C2 -C3 H3 -C3 -C2 H3 -C3 -C4 H4 -C4 -C3 H4 -C4 -B H5 -C5 -N HS -cs -C6 H5 -cs -C7 H6A -C6 -cs H6B -C6 -CS H6C -C6 -CS H6B -C6 -H6A H6C -C6 -H6A H6C -C6 -H6B H7A -C7 -CS H7B -C7 -CS H7C -C7 -CS H7B -C7 -H7A H7C -C7 -H7A H7C -C7 -H7B HS -CS -N 107.8 107.5 111.8 111.2 109.5 108.7 108.8 108.5 110.6 110.2 110.0 125.6 125.8 125.5 124.8 124.6 124.4 126.2 126.8 99 .7 93 .9 97.7 108.1 108.6 108.9 109.7 110.7 110.7 108.5 108.8 108.6 110.7 109.9 110.3 100.6 134 Table VI. (Continued) -C8 -C9 H8 -C8 -C10 H8 H9A -C9 -C8 H9B -C9 -C8 H9C -C9 -C8 H9B -C9 -H9A H9C -C9 -H9A H9C -C9 -H9B H10A -C10 -C8 H10B -C10 -C8 H10C -C10 -C8 H10B -C10 -H10A H10C -C10 -H10A H10C -C10 -H10B HllA -Cll -01 H11B -C11 -01 H11A -Cll -C12 H11B -C11 -C12 HUB -C11 -H11A H12A -C12 -C11 H12B -C12 -C11 H12C -C12 -Cll H12B -C12 -H12A H12C -C12 -H12A H12C -C12 -H12B H13A -C13 -01 H13B -C13 -01 H13A -C13 -C14 H13B -C13 -C14 H13B -C13 -H13A H14A -C14 -C13 H14B -C14 -C13 H14C -C14 -C13 H14B -C14 -H14A H14C -C14 -H14A 93.8 102.1 109.2 109.2 108.7 110.2 109.4 110.1 109.2 107.8 108.5 110.2 111.3 109.8 109.1 109.1 109.1 109.3 109.9 108.1 108.7 108.8 110.2 110.2 110.8 103.3 106.7 103.9 109.7 109.9 107.7 105.7 111.7 108.1 112.7 H14C -C14 -H14B H15A -C15 -02 H15B -C15 -02 H16B -C15 -02 H15A -C15 -C16 H15B -C15 -C16 H16B -C15 -C16 H15B -C15 -H15A H16B -C15 -H15A H16B -C15 -H15B H16A -C16 -C15 H16B -C16 -C15 H16C -C16 -C15 H16B -C16 -H16A H16C -C16 -H16A H16C -C16 -H16B H17A -C17 -02 H17B -C17 -02 H17A -C17 -C18 H17B -C17 -C18 H17B -C17 -H17A H18A -C18 -C17 H18B -C18 -C17 H18C -C18 -C17 H18B -C18 -H18A H18C -C18 -H18A H18C -C18 -H18B 110.7 100.5 104.8 103.9 105.8 115.5 35.5 107.9 141.2 94.4 103.4 103.6 113.2 107.6 113.3 114.8 101.7 107.2 103.7 115.8 107.9 104.8 101.6 113.6 107.2 115.1 113.3 135 Table VII. Assigned Hydrogen Atom Parameters for Cp•(4!-4BNi Pr2)ZrCl· UCl(Et20h (27). z, y a.nd z x 1o• Atom z y z B HM1A HM1B HM1C HM2A HM2B HM2C HM3A HM3B HM3C HM4A HM4B HM4C HM5A HM5B HM5C H1 H2 H3 H4 H5 H6A H6B H6C H7A H7B H7C H8 H9A H9B H9C H10A 6096 5146 5017 3888 5264 4600 3206 2661 4035 2590 3972 3232 4844 4751 3580 2943 3228 1284 -319 -1161 -983 -2268 -1737 -1217 -1891 -2423 175 798 2115 1248 1112 2340 2149 2785 3095 2917 3213 2343 1671 1775 526 376 669 1124 592 827 3268 2475 1935 2295 3098 3097 3105 3710 3930 4256 3651 4272 4560 4460 4923 3588 5167 5844 5321 2856 3035 3329 1841 1791 1664 3378 3359 2489 5711 4972 5385 4702 5986 6128 4863 4062 2591 2941 2554 4990 4128 4515 3365 4739 4479 3911 2471 12.1 12.1 12.1 12.4 12.4 12.4 13.7 13.7 13.7 12.6 12.6 12.6 10.3 10.3 10.3 5.9 8.0 7.8 6.0 9.1 12.6 12.6 12.6 11.2 11.2 11.2 10.1 10.8 10.8 10.8 11.5 136 Table VII. (Continued) HlOB HlOC H11A H11B H12A H12B H12C H13A H13B H14A H14B H14C H15A H15B H16A H16B H16C H17A H17B H18A H18B H18C 1455 2322 -3247 -2216 -3934 -2938 -3969 -2973 -3176 -2685 -1688 -1484 -718 -1027 -24 626 935 -461 727 -428 -221 -1409 4288 3826 1816 1723 1282 779 872 1494 806 880 2429 2997 2894 2253 1633 1872 2514 4253 3945 5375 530 4895 5203 1219 201 887 797 1016 1242 274 11 .5 11 .5 13.5 13.5 15.8 15.8 15.8 22.4 22.4 17.1 17.1 17.1 16.0 16.0 15.8 15.8 15.8 28.8 1118 432 -382 -293 1151 924 1886 -838 3016 3587 28.8 20.9 20.9 2924 20.9 -227 -316 2548