The Reactivity of Zirconium Hydrides with Transition Metal Carbonyls Citation Barger, Paul Theron (1983) The Reactivity of Zirconium Hydrides with Transition Metal Carbonyls. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/qvev-5987. https://resolver.caltech.edu/CaltechTHESIS:09262018-130043347 Abstract The reactivity of bis(pentamethylcyclopentadienyl) zirconium hydride complexes with a variety of Group VIII transition metal carbonyls has been investigated. These reactions are observed to follow two distinct pathways; one involving reductive loss of the zirconium hydrides as H 2 , the other proceeding by. hydride transfer to the carbon atom of a carbonyl to afford CO reduction. Treatment of CpM(CO) 2 (M=Co, Rh, RuH) with Cp 2 *ZrH 2 or [Cp 2 *ZrN 2 ] 2 N 2 (Cp=C 5 H 5 , Cp*=C 5 Me 5 ) give the "early" and "late" metal dimers, CpM(CO) 2 ZrCp 2 *: with elimination of H 2 or N 2 . The X-ray crystal structure of CpCo(CO) 2 ZrCp 2 *; is reported and shows that this molecule contains a Co-Zr single bond bridged by a conventionally bound μ-CO and a four-electron donating μ-η 1 , η 1 CO. The reactions of Cp 2 *ZrHX (X=F, Cl) with these carbonyls proceed by the second pathway to give oxycarbene complexes, Cp(CO)M=CHO-Zr(X)Cp 2 * (M=Co, Rh). These compounds demonstrate that the zirconium hydride reduction of a Group VIII metal carbonyl is reversible; an equilibrium is observed between the carbene complexes and the starting metal dicarbonyl and ziconium hydride. Treatment of CpM(CO)(PMe 3 )H or CpM(CO) 2 CH 3 (M=Fe, Ru) with Cp 2 *ZrH 2 , in the presence of PMe 3 , affords Cp(PMe 3 ) 2 M-CH 2 O-Zr(H)Cp 2 * or Cp 2 *Zr(OCH=CH 2 )H. The mechanisms of the transformation are proposed to involve initial formation of an iron or ruthenium oxycarbene intermediate which undergoes migratory insertion into the metal hydride or alkyl bond followed by phosphine trapping or β-elimination to give the observed products. Several zirconium oxycarbene complexes have been prepared by the reduction of the corresponding zirconium carbonyl by Cp 2 *ZrH 2 . These molecules represent some of the first isolable examples of Group IV metal to carbon multiple bonding. The X-ray crystal structure of Cp 2 (PMe 3 )Zr=CHO-Zr(I)Cp 2 * • C 6 H 6 is reported. Treatment of Cp 2 (CO)Zr=CHO-Zr(H)Cp 2 * with MeI or Cp 2 (PMe 3 )Zr=CHO-Zr(I)Cp 2 * with CO gives a new product, the structure of which has been shown by X-ray diffraction to be Cp 2 *ZrOCH=C(Zr(I)Cp 2 *)O. The mechanism for this transformation has been shown to involve an intramolecular coupling of carbene and carbonyl ligands on a zirconium center to give a zirconium ketene intermediate, which rearranges to the observed product. In the presence of pyridine the ketene intermediate can be trapped to give the isolable Cp 2 (pyr)Zr(O=C=CHO-Zr(H)Cp 2 *). 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): Grubbs, Robert H. Thesis Committee: Grubbs, Robert H. (chair) Bercaw, John E. Dougherty, Dennis A. Collins, Terrence J. Defense Date: 23 April 1983 Record Number: CaltechTHESIS:09262018-130043347 Persistent URL: https://resolver.caltech.edu/CaltechTHESIS:09262018-130043347 DOI: 10.7907/qvev-5987 Default Usage Policy: No commercial reproduction, distribution, display or performance rights in this work are provided. ID Code: 11200 Collection: CaltechTHESIS Deposited By: Mel Ray Deposited On: 02 Oct 2018 18:13 Last Modified: 24 Jul 2025 23:12 Thesis Files Preview PDF - Final Version See Usage Policy. 62MB Repository Staff Only: item control page

THE REACTIVITY OF ZIRCONIUM HYDRIDES WITH TRANSITION METAL CARBONYLS Thesis by Paul Theron Barger In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy California InstitUte of Technology Pasadena, California 1983 (Submitted April 27, 1983) ii to Mom and Dad iii ~~~ I wish to thank all the members of the Bercaw group, past and present, for providing a stimulating environment in which to both do science and have fun. All have taught me something about chemistry. The groundwork in the chemistry of Cp:zrH 2 by Juan Manriquez, Bob Sanner, Don McAlister, Pete Wolczanski and Rich Threlkel made my entry into this field significantly easier. The crystallographic work described in Chapter II of Bernard Santarsiero and Justine Armantrout is gratefully acknowledged. Bernie was also very helpful in proofreading portions of this thesis. The expert typing of Henriette Wymar is greatly appreciated. Some of the best times I have had during the last four years have been on the hiking or biking trail. I wish to thank all the people, fortunately too numerous to mention individually, who have shared these experiences with me. The superb guidance, financial support and overall good sense of John Bercaw as my research advisor has made my graduate career at Caltech extremely valuable. It is nice to finish nearly five years of graduate school knowing I made some right decisions when I was young and ignorant; deciding to work for John was one of my best. Finally, I am very grateful for the love and understanding of my parents and family. iv Abstract ~ The reactivity of bis(pentamethylcyclopentadienyl) zirconium hydride complexes with a variety of Group VIII transition metal carbonyls has been investigated. These reactions are observed to follow two distinct pathways; one involving reductive loss of the zirconium hydrides as H2 , the other proceeding by. hydride transfer to the carbon atom of a carbonyl to afford CO reduction. Treatment of CpM(C0) 2 (M =Co, Rh, RuH) with C~ZrH2 or [C~ZrN2 ] 2 N2 (Cp = C5H5 , Cp* = C5Me 5) give the "early" and "late" metal dimers, CpM(C0) 2 ZrCp: with elimination of H2 or N2 • The X-ray crystal structure of CpCo(C0) 2 Zrcp; is reported and shows that this molecule contains a Co-Zr single bond bridged by a conventionally bound µ-CO and a four-electron donating µ-TJ 1 , .,, 2 CO. The reactions of C~ZrHX (X = F, Cl) with these carbonyls proceed by the second pathway to give oxycarbene complexes, Cp(CO)M = CHO-Zr(X)C~ (M =Co, Rh). These compounds demonstrate that the zirconium hydride reduction of a Group vm metal carbonyl is reversible; an equilibrium is observed between the carbene complexes and the starting metal dicarbonyl and ziconium hydride. Treatment of CpM(CO)(PMe3 )H or CpM(C0) 2 CH3 (M = Fe, Ru) with C~ZrH2 , in the presence of PMe3 , affords Cp(PMe 3 ) 2M-CH 20-Zr(H)C~ or C~Zr(OCH=CH 2 )H. The mechanisms of the transformation are proposed to involve initial formation of an iron or ruthenium oxycarbene 'intermediate which undergoes migratory insertion into the metal hydride or alkyl bond followed by phosphine trapping or tJ-elimination to give the observed products. v Several zirconium oxycarbene complexes have been prepared by the reduction of the corresponding zirconium carbonyl by C~ZrH 2 • These molecules represent some of the first isolable examples of Group IV metal to carbon multiple bonding. The X-ray crystal structure of C1>2(PMe 3 )Zr=CHO-Zr(I)C~ • CJI 6 is reported. Treatment of C1>2(CO)Zr=CHO-Zr(H)Cp: with Mel or C1>2(PMe3 )Zr=CHO-Zr(I)C~ with CO gives a new product, the struc- ture of which has been shown by X-ray diffraction to be C~ZrOCH=C(Zr(I)CP:,.)0. The mechanism for this transformation has been shown to involve an intramolecular coupling of carbene and carbonyl ligands on a zirconium center to give a zirconium ketene intermediate, which rearranges to the observed product. In the presence of pyridine the ketene intermediate can be trapped to give the isolable CP:,.(pyr)Zr(O=C=CHO-Zr(H)C~). vi Table of Contents Page 1 Introduction Chapter I. The Reactivity of Bis(pentamethylcyclo- 11 pentadienyl} Zirconium Hydrides with Group VITI Transition Metal Carbonyls. Chapter II. Synthesis and Reactivity of Some Zirconium Oxycarbene Complexes. SS 1 INTRODUCTION 2 The recent demand for alternative chemical feedstocks other than petroleum has revived a major interest in the reduction of carbon monoxide by H2 to make simple oxygenates, such as methanol and ethylene glycol. While there has been a significant amount of work in this field using heterogeneous catalysts, 1 for example, the synthesis of methanol using Zn-Cu catalysts, 2 some of the best studied systems have been homogeneous in nature. Solutions of HCo(C0) 3 and Ru(C0) 4 5 4 have been observed to catalyze the hydrogenation of CO to alcohols and formates, as have mixtures of Cp2 ZrC~ and aluminum hydrides. 5 The synthesis of ethylene glycol from CO and H2 using rhodium carbonyl clusters 6 demonstrates the selectivity possible by the use of homogenous catalysts. While transition metal hydride intermediates are often invoked in speculative mechanism of these CO reductions, 7 C~ZrH remains 2 the only isolable transition metal hydride complex clearly shown to act as a hydride transfer agent to the carbon atom of a metal carbonyl. a,9 This reactivity is similar to that seen for borohydride reagents, such as Li(C2H5 ) 3 BH, with rhenium carbonyls to cleanly afford formyl products. 1 O The first report that bis(pentamethylcyclopertadienyl) zirconium compounds were useful for CO reduction was that of the hydr~enation of ci;·zr(C0) 2 at 110• C to give C~Zr(OCH 3 )H. 11 It was also observed that under an atmosphere of CO at 25• C C~ZrH2 affords equal quantities of C~Zr(OCH )H and C~Zr(C0) • 11 At temperatures below . 3 2 3 -5o• C a carbonyl adduct, C~ZrH 2 (CO) can be observed; however, on war~ing to room t~mperature this intermedia~e gives trans- [cp:ZrH]2 ( µ-OCH=CHO-), {cp:ZrH)2( µ-OCH2CH20-), C~Zr(OCH3 )H and Cp:Zr(C0) 2 in ratios depending on the reaction conditions. 12 Two mechanisms have been proposed for these trans- formations that differ only in the way that hydrogen is transferred to the carbonyl carbon. 13 In Scheme I migratory insertion of CO into a zirconium hydride bond to give a formyl intermediate, followed by intermolecular reduction of the formyl carbonyl by a second equivalent of C~ZrH 2 affords C~(H)Zr-CH 20-Zr(H)C~, a common intermediate to the two mechanisms. The recent report of a thorium formyl complex, prepared by the low-temperature carbonylation of Cp:Th(H)(OtBu), 14 provides good precedence of invoking the un~ common insertion of CO into a metal hydride bond in Scheme I. An alternative mechanism, Scheme II, proceeds by initial reduction of the zirconocene dihydride carbonyl adduct by C~ZrH2 to give an oxycarbene intermediate which would be expected to rapidly insert into one of the zirconium hydride bonds to give C~(H)Zr-CH 20-Zr(H)Cp:. This mechanism is supported by the preparation of tungsten8 and niobium 9 oxycarbene complexes by the treatment of the corresponding carbonyls with C~ZrH2 and by the ability of the niobium carbenes to insert into metal hydride and alkyl bonds. 9 The carbonyls of C~Zr(C0) 2 are als.o reduced by C~ZrH2 under H2 at · 25• C, to give cis-(C~ZrH) 2 ( µ-OCH=CHO-). 12a, 9 That the stereochemistry of this product is different from that of the previously described enediolate dimer indicates that an independent mechanism is i I J: 'I /:i: l N '- 'u--'o :c J: ~ 1 0 u N __ / ' u'1 :I: I /:r. 1 0 .... N + u N "- ,,/ J: ' .... ~ c .2 a - -~ 'CD E ~ 4 .. 0 II (.J / :c~, , N ' 0 % J: __ __,J: / ·' % ~, 0 "- /N 0N :I: __ /r. ~ u, / N ' £i .... "- N .., + J: 8 ' ~ .§ 0 .5 .§ -• ' :i: / u 0 • r. __ N .... 0 I J: /u J: ~ /~ / , ' "- N l o-u I N r/ ':c :I: /:x: t N""" u, I ~/o "- N 0 / 'J: N J: u, , u/l__ / :c N Scheme II /H Zr 1 /H '\, +CO• .. Zr-CO .. /H /O'\. 'H \ H HI '-H 'H Zr Zr.+C 1 /\ Zr~o \ c, / Zr H/ 4 I \ H /0 Zr I CH 0 .. Zr-O '\.H H/ 7 '\, /CHzO, . ... Zr/CHzO'zr lHz 2, / Zr / OCH 3 ZrH2 + Zr '\. H (Jl H H 1 H'- 'c H/ 'cHzO/ Zr o /3-H elimination - - - - -... - Zr / \ HH ' / \ C;:::: C Zr I HH 'o/ 6 operating in this reaction. It was initially proposed that a bis-carbene intermediate was formed, followed by carbene coupling to give the observed product (Scheme III). 13 However, the reaction of cp:Zr(C0} with C~Hffi2 gives only the mixed metal enediolate complex, 2 14 dis- crediting this mechanism. The mechanism presently in favor (Scheme IV) involves initial formation of a zirconium carbene carbonyl complex that undergoes ligand coupling to coordinated ketene intermediate which is hydrogenated to give bis-(cp:zrH)(µ-OCH=CHO-). 13 This thesis reports on our further investigations of the reactivity of bis(pentmethylcyclopentadienyl} zirconium hydrides with Group VIII and Group IV transition metal carbonyls in an attempt to gain additional understanding of the mechanisms of CO reduction. 7 Scheme III /co Zr '\;...::::lo :: = Zr H / " H --... 8 Scheme IV /co Cp~Zr(C0)2 + Cp~ZrH 2 -... • Cp~Zr 'c-OZrCp~ I H ! /0 CpfZr I 'c 'c-OZrCp~ I I H H CH=CH I Cp~Zr/0 'H °' \ ZrCp~ H/ I H 9 References ~ 1. Denny, P . J.; Whan, D. A. in "Catalysis", The Chemical Society: London, (1978), p. 46. 2. Herman, R. G.; Klier, K.; Simmons, G. W.; Finn, B. P.; Bulko, J. B.; Kobylinski, T. P. Jo Catal. ~' 407 (1979) . 3. (a) Rathke, J. W.; Feder, H. M. J. A.mer. Chem. Soc. 100, ~ 3623 (1978); (b) Feder, H. F.; Rathke, J. W., Ann. N. Y. A.cad. Sci. 333, ~ 45 (1980). 4. (a) Bradly, J. S. J. Amer. Chem. Soc. 101, 7419 (1979); ---------~ (b) Dombek, B. D. _J_._A_m_e_r_._C_h_e_m_._So_c_. _!Sg, 6857 (1980). 5. Shoer, L. I.; Schwartz, J. J. Amer. Chem. Soc. 99, 5831 """"" (1977). 6. Pruett, R. L.;Walker, W. E. (Union Carbide Corp.), West German Patent 2 262 318 (1972); U.S. Appl. 210 530 (1971). 7. Masters, C. Adv. Organomet. Chem • .!1, 61 (1979) and references therein. 8. Wolczanski, P. T.; Threlkel, R. S.; Bercaw, J. E. J. Amer. Chem. Soc. 101, 218 (1978). ~ 9. Threlkel, R. S.; Bercaw, J. E. J. Amer. Chem. Soc. 103, ~ 2650 (1981). 10. (a) Casey, C. P.; Andrew, M. A.; Rinz, J. E. J. Amer. Chem. Soc. 101, 741 (1979); -~ ·(b) Tam, W.;Wong, W.-K.;Gladysz, J. A. J. Amer. Chem. Soc., !Q!., 1589 (1979); 10 (c) Sweet, J. R.; Graham, W. A. G. J. Organomet. Chem. 173, C9 (1979). ~ 11. Manriquez, J. M.; Sanner, R. D.; Marsh, R. E.; Bercaw, J. E. J. Amer. Chem. Soc. 98, 6733 (1976). """"' 12. (a) Manriquez, J. M.; McAlister, D. R.; Sanner, R. D.; Bercaw, J. E. J. Amer. Chem. Soc. 100, 2716 (1978); ~ (b) Curtis, C. J. ; Bereaw, J. E. , unpublished results. 13. Wolczanski, P. T.; Bercaw, J. E. Acc. Cheni. Res. ]1, 121 (1980). 14. Fagan, P. J.; Moloy, K. G.; Marks, T. J. J. Amer. Chem. Soc. 103, 6959 (1981). -"""""' 15. Roddick, D. M.; Bercaw, J. E., unpublished results. 11 CHAPTER I The Reactivity of Bis(pentamethylcyclopentadienyl) Zirconium Hydrides with Group VIII Transition Metal Carbonyls 12 Introduction ~ In view of the ease with which C~ZrH 2 (!) reduces Groups V and VI transition metal carbonyls to the corresponding oxycarbene complexes1 we have investigated the reactions of !. and related hydrides * . . . .--H LnM(CO) + Cp2 ZrH 2 _. LnM=C"-.. * O-ZrCP2 (1) I H with other metal carbonyls. The major goals of this research have been to explore the generality of the zirconium hydride reduction of metal bound CO and to probe the reactivity of the oxycarbenes prepared by this technique. Prior to this work cp;Zr(C0) 2 was the only transition metal dicarbonyl complex observed to give a clean product upon treatment with C~ZrH , affording cis-(cp:zrH) (µ-0CH=CH0-) 1b, 2 in which 2 2 (2) both carbonyls have been reduced and a new carbon-carbon bond formed. Unfortunately, no intermediates could be identified during the course of this reaction to provide information as to the mechanism of this unique transformation. We were therefore interested in the - reactivity of 1 with other transition metal dicarbonyl complexes to gain some understanding of reaction pathways available to compounds of this type. 13 A second area of interest centered on molecules containing zirconoxy carbene and a hydride or alkyl ligand on one metal center. Niobium complexes of this type have been previously observed to undergo migratory insertion of the carbene ligand into the metal hydride or alkyl bond. 1b There are few reports of this type of insertion; 3 therefore we have attempted to prepare some carbenehydride and carbene-alkyl complexes of iron and ruthenium to gain further insight about the mechanism of the migratory insertion. This chapter reports our investigations of the reactions of cp;zrHX (X = H, F, Cl) with a variety of Group VIII transition metal mono- and dicarbonyl complexes. These reactions have been observed to follow two different reaction pathways. The first proceeds by reductive elimination of the zirconium hydride ligands as H2 , followed by trapping of the zirconium(II) fragment by the metal carbonyl complex to afford an "early" and "late" mixed-metal dimer. The second class involves CO reduction by the zirconium hydride, giving Group VIII metal oxycarbene complexes or products arising from oxycarbene intermediates. A preliminary report of a portion of this work has . prm . t. 4 appeare d 1n 14 Results ~ Reactivity of Zirconium Hydrides with Cobalt and Rhodium Carbonyls. Opposed to the observed reactivity of C~ZrH 2 (!) with several transition metal monocarbonyls to afford oxycarbene complexes, 1 the treatment of CpM(C0) 2 (M =Co(~), Rh(~) with!. in toluene yields CpM(C0) 2 ZrCp: (M =Co(~, Rh(~)) where the zirconium hydrides are lost as H2 and a new metal-metal bond is formed between the zirconium and cobalt or rhodium. The zirconium-cobalt dimer forms (3) - -1 2 3 (M =Co, Rh) at ca. -20•, as indicated by a colorlehange of the reaction solution from red to blue-green, and can be isolated as dark green crystals in 46% yield. In contrast, a mixture of CpRh(C0) 2 and!. in a sealed NMR tube shows the initial formation of an intermediate with a down-field resonance in the 1H NM.R spectrum suggesting the presence of a zirconoxy carbene ligand. Over several minutes this transient species -mixture. converts to 3b, the only product that can be isolated from the reaction 1 The H NMR spectra (Table I) of .,..-., 3a and .,..-., 3b are very similar, showing only two resonances due to the Cp and Cp* ligands. The m spectra have two intense bands, at 1737 and 1683 cm- 1 for~ and 1752 and 1696 cm -i for 3b, assigned as the stretching frequencies of the """"" remaining carbonyls. That neither band shows a shift to lower energy in them spectrum of~ prepared from~ and C~ZrD2 indicates that these bands are not due to any remaining metal hydrides. 15 The liberation of dihydrogen during the course of the reaction is confirmed by the recovery of 0. S3 equivalents of H2 per equivalent of CNZrH2 by a Toepler pump after the formation of~· CpM(C0) 2 ZrC~ can also be prepared from~ arid [C~ZrN2 ] 2 N2 , with the loss of 1. 5 equivalents of N2 , providing further evidence for the presence of zirconium in the +2 oxidation state in the product. - - 2 3 (M =Co, Rh) Under an atmosphere of CO in a sealed NMR tube 3a cleanly """"" converts to CpCo(C0) 2 and C~Zr(C0) 2 after 5 hours at S0°C. The CpCo(C0) 2 ZrC~ +CO so• c, CpCo(C0) 2 + Cp:Zr(C0) 2 (5) reaction of~ with H2 at so• C affords C~Zr(OCH 3 )(H) and CpCo(C0) 2 as the major products, but the 1 H :mdR spectrum of the reaction solution indicates the presence of several other, unidentified products. We were interested in the detailed structure of 3a for several """"" reasons. CpCo(C0) 2 Zrcµ; is the first known heterometallic dimer containing zirconium and cobalt. Interestingly, there appear to be no reasonable symmetric structure.s which allow formal 18-electron, closed-shell electronic configurations for both metals. This fact, along with the low energy vco stretching frequencies, suggested that the carbonyls of 3a might bridge the Co-Zr bond in a non-conventional """"" fashion. Therefore, the structure was investigated using X-ray diffraction techniques. 16 Single crystals of ~' suitable for X-ray diffraction, were grown by slow cooling of a saturated benzene solution. Unit cell parameters as well as data collection and refinement conditions are given in Table II. Atomic positions and Gaussian amplitudes for all atoms are listed in Table III. Tables IV and V give bond distances and angles. The ORTEPs of -""-"" 3a (Figures 1 and 2) confirm its formulation as CpCo(I) and cp;Zr(II) moieties joined by a Co-Zr bond and two bridging carbonyls. The Cp and Cp* ligands are bound to the metals in a standard pentahapto manner. The Zr-C(rings) distances (2. 501(6)2.' 589(6) .A) and the Cp* ring centroid-zirconium-Cp* ring centroid angle of 139. 2(5) e are similar to those of [C~ZrN ] N • 5 The 2 2 2 Co-C(ring) distances (2. 081(7)-2.106(7) A) are typical for a 77 5 -C 5H5 ring bound to Co(I). 6 The Cp ring centroid is skewed off the Co-Zr axis by 11. 7 ° toward the µ 2 bridging carbonyl, presumably due to the different trans electronic effects of the two carbonyls. CpCo(C0) 2 Zrcp; is the first example of a molecule with a bond between zirconium and a Group VIII transition metal. The metal-metal distance of 2. 926(1) A can be compared to that observed for Cp (CO)Nb(µ-CO)Co(C0) of 2. 992 A, 7 another example of an "early" 2 3 to "late" transition metal bond. This bond length indicates the presence of a Co-Zr single bond. One of the most interesting features of the structure of 3a is that the two carbonyls have very different bonding interactions with the two metai centers. The metal-carbonyl substructure (Figure 2) is essentially planar as is demonstrated by the small deviations from the leastsquares plane of the metal and carbonyl atoms (Table VI). 17 Figure 1. ORTEP drawing of CpCo(C0} 2 Zrcp: showing 50% probability ellipsoids for non-hydrogen atoms. 18 2.926(1} Cp Figure 2. ORTEP drawing of the planar metal-carbonyl substructure, including important bond lengths (A) and angles. 19 One carbonyl, C(2)-0(2), bridges the metal centers in a conventional µ 2 fashion, although there is some inherent asymmetry due to the large difference in size of the two metals. The other carbonyl, C(l )-0(1), interacts with the two metals in an unique µ 2 -11 1 , 17 2 manner. The nearly linear C o-C(l )-0(1) angle (176. 7(7) 0 ) and short Co-C(l) distance (1. 689(8) A) indicate that the cobalt-carbonyl bonding is essentially terminal. Both C(l) and O(l) are well within bonding distance to the Zr, indicative of interaction of a C(l)O(l) 1T bond with zirconium similar to that observed for ethylene in Cp Nb(C H )(C H }. 8 The lengthening of the C(l)-0(1) distance from 2 2 4 2 5 that normally observed for terminal cobalt carbonyls 9 also supports a zirconium-carbonyl 7T-interaction, as donation of electron density to the metal center lowers the C-0 bond order. This is also consistent with the very low m stretching frequency assigned to this carbonyl. Since there is only one orbital in the equatorial wedge of the zirconocene center for bonding to C(l)O(l) in 3a this interaction cannot be ""'"" regarded as similar to that of the 1i2-acyl in Cp2 Zr(77 2 -COCH 3)(CH 3 ) 10 where the carbon and oxygen atoms interact with different metal 2 orbitalso Thus in the µ-n 1 , n bridging mode the carbonwl acts as a two-electron donor to both the cobalt and zirconium, bringing both metal centers to closed-shell, 18-electron configurations. The 13 C NMR spectrum of CpRh(C0) 2 ZrC~ enriched with 13 CO has only one resonance for the carbonyls at room temperature (254 6, 1 JC-Rh = 59 Hz) indicating that the two carbonyls are rapidly inter- chang~ng bonding modes. Variable temperature 22. 5 MHz NMR spectra show coalescence of this resonance at ca. -60° C, but attempts 20 to observe the low temperature limit, where the carbonyls are inequivalent, were unsuccessful at this field strength. However, the 125. 8 l\tIHz spectrum at -70• C shows to broad resonances at 298 and 215 ~' assigned as the res:onances of the carbonyls in the two different bonding modes. The chemical shift difference and the coalescence temperature give an upper limit of 8 kcal/mole for the activation barrier of the fiuxional process. The reductive elimination of H2 from !. that leads to the formation of the mixed-metal dimers can be prevented by replacement of one of the zirconium hydrides by a halide. Thus, treatment of an excess of ~with C~ZrHCl (1) in toluene affords the cobalt or rhodium zirconoxy · carbene complexes, Cp(CO)M=CHO-Zr(Cl)C~ (M =Co(~), Rh(~) in good yield after 2 hours at room temperature. The carbene complexes CpM==CHO-ZrC~ CpM(C0)2 + Cp:ZrHCl 2 I CO 4 I Cl 5 (6) {M =Co, Rh) can be isolated free of dicarbonyl by precipitation with pet ether at -78• C. The corresponding fluoride carbene complexes Cl) can be prepared in an analogous manner using C~ZrHF (§) in place of cp:zrHCl. CpM(C0) 2 + C~ZrHF _. CpM==CHO-ZrC~ J 2 CO 6 - I 7 F (7) (M = Co, Rh) The 1H NMR spectra of 5 (Table I) show resonances attributable to the Cp and Cp* ligands as well as a down-field peak(~, 12. 6 o; 21 5b, 13. lo), integrating to one proton, for the carbene hydrogen. The ,,.--. m spectra of nujol mulls of §. show one strong band in the CO stretching region at 1947 cm-1 for ,,.--. 5a and 1952 cm- 1 for 5b. The 1H NMR and IR ~ - spectra for 7 (Table I) are similar. The equilibrium depicted in equation 6, between the zirconoxy carbene complex and the Group VIII dicarbonyl and C~ZrHCl can be attained from either direction. Thus at the completion of the reaction - - of 2 and 4 both starting materials can be observed in the reaction mixture. Likewise, resonances due to! and 1. slowly grow into the - 1H' NMR spectra of isolated 5 over several days. In the case of 5a the ~ equilibrium consists of approximately 70% Cp(CO)Co=CHO-Zr(Cl)Cp: to 30% CpCo(C0) 2 and C~ZrHCl; for §.R the observed ratio is about -In the presence of protic acids, HX (X = Cl-, PhCOO-), 5b is 90:10, 5b to 2b and 4. ~ """" rapidly converted to CpRh(C0) 2 and cp:Zr(Cl)(X) at 25• C with the evolution H2 • Attempts to prepare amine-substituted rhodium carbene CpRh=CHO-ZrC~ + HX --+ CpRh(COh + C~Zr(Cl)(X) + H2 I I CO 5b Cl 2b (8) complexes by aminolysis of ~with HNMe2 , a reaction pathway that is common for Fischer-type carbenes, 11 have been unsuccessful. (9) Cp(CO)Rh=CHO=Zr(Cl)Cp: is unaffected by an excess of Cp:ZrHCl indicating that the remaining carlx> nyl is inert toward reduction to give 22 a bis-carbene complex. CpRh=CHO-ZrC~ + Cp:ZrHCl CO I -5b Cl H Cl I I * ~C-0-ZrC~ II) CpRhg: "=C-0-ZrC~ I 4 H I Cl (10) Reactivity of Zirconium Hydrides with Iron and Ruthenium Carbonyls. Addition of Cp:ZrH2 to a heptane solution of CpRu(C0) 2 H (fil affords the dark red Cp(H)Ru(C0) 2 ZrC~ (!!) in 59% isolated yield after one hour at room temperatures. Like CpM(C0) 2 ZrC~ (M = Co, Rh), CpRu(CO)~ + Cp:ZrH2 ~ ~can 8 1 also be prepared Cp(H)Ru(C0)1.ZrC1>a* 9 (11) - from~ and [cp:ZrN2 ] 2 N2 with the liberation of 2.56 equivalents of N2 per equivalent of [C~ZrN2 ] 2 N2 as measured by Toepler pump. The m spectrum of a nujol mull of 9 is similar to - CpRu(C0) 2 H + [C~ZrN2 ] 2 N2 __. Cp(H)Ru(G_0) 2 Zr~p: + iN2 8 9 -- - (12) - those of 5a and 5b and shows two intense bands in the carbonyl """"'"" - stretching region at 1706 and 1671 cm- 1 • The 1H NMR spectrum of 9 (Table I) shows a peak at 5. 17 o for the Cp ring on Ru and two resonances for the Cp* rings at 1. 67 and 1. 74 o. A small peak, integrating to one proton, appears at -15. 7 o and is _assigned as the signal of a remaining ruthenium hydride. These results suggest the structure of - - 9 is similar to those of 3 with Cp and hydride ligands on opposite sides of the metal-carbonyl plane, making the Cp* rings inequivalent. 23 cp~. _ /c ·~Ru H.,,,,,,,,,,,,,- ~o °"'CII 7 \ ,•.... cp* ~Cp * Zr 1' 0 9 - Treatment of 9 with an excess of CO gives a mixture of CpRu(C0) 2H and C~Zr(C0) 2 after a4 hours at room temperature. Replacement of one of the carbonyls of ~by PMe3 , giving Cp;M:(CO)(PMe3 )H (M =Fe(~), Ru(W)), prevents formatio~ of a mixed-metal dimer upon treatment with Cp:ZrH2 • Instead, a - solution of 10 and 1 shows no change by NMR spectroscopy """' after 7 weeks at room temperature. However, addition of 4 equivalents of PMe3 to a solution of !!&.: and !. affords Cp(PMe 3 ) 2 Fe-CH 20-Zr(H)C~ (!]&} in 51% isolated yield after - 10 minutes at room temperature. In the case of lOb the formation of Cp(PMe 3 ) 2 Ru-CH 2 0-Zr(H)C~ (ill) is significantly slower; after sealed NMR tube is at 75% completion; increasing the PMe concen3 weeks at 25 ° C a mixture of 1 Ob, 1, and 2 equivalents of PMe. in a . """"""' 3 tration to 10 equivalents does not significantly affect the rate of formation of llb. """""' CpM(CO)(PMe3 )H + C1J2*ZrH2 PM~ ~ Cp(PMe3 ) 2 M-CH20-Zr(H)CP2* 10 ,,....,.... - -- 1 11 (M = Fe, Ru) (13) The 1H NMR spectrum of 1 la (Table I) is consistent with its --- formulation as a methylene oxo bridged dimer. The presence of two 24 phosphine ligands on the iron center is clearly indicated by the pseudo triplet pattern of the resonance due to the methyl groups on phosphorus and the triplet splitting ( 2 JPH = 2 Hz) of the Cp resonance at 3. 87 o. A broad peak at 5. 26 o, integrating to one proton, is assigned as the resonance of the remaining zirconium hydride. The signal for the methylene group appears as a triplet due to phosphorus coupling at 5. 07 o. The 1H NMR spectrum of llb (Table I) is more complicated """""" than that of lla. The phosphine methyl resonance appears as a com""""""" plex multiplet centered at 1.11 o. Unlike the spectrum of lla, the - - resonance for the ruthenium Cp of 11 b is a singlet similar to that - observed in the spectrum of lOb. The methylene protons give rise to an apparent doublet of doublets centered at 5. 32 o in both the 90 MHz and 500 MHz spectra; the splitting patterns are similar at the two different fields suggesting that the two protons are magnetically equivalent and being split by two inequivalent phosphorus atoms. At the present time no satisfactory explanation for the differences in - the spectra of 1la and 11 b has been developed. ,._.,,..... In the absence of PMe3 the hydride ligands of .!.!& and !. readily exchange between the two metal centers. Treatment of a mixture of .!.!& and !. with a large excess of D2 at 0° C for 1 hour places deuterium into both iron and zirconium hydride sites. The hydrides of C~ZrH 2 CpFe(CO)(PMe3 )H + Cp:ZrH2 !Q ! XS D2 * > CpFe(CO)(PMe3 )D + Cp2 Zr~ ~ (14) are known to rapidly exchange with D2 , 12 however, CpFe(CO)(PMe3 )H alone is inert to D2 under these conditions indicating that the exchange 25 between D2 and the iron hydride is catalyzed by 1 (Scheme I). The reactions of C~ZrH 2 and the dicarbonyl, alkyl complexes CpM(COhCH3 (M = Fe(~, Ru (12b)) also proceed by a pathway involving CO reduction, rather than yielding a mixed-metal dimer - analogous to 9. - Thus, a mixture of 12b and 1 with 2 equivalents of """" PMe3 in a sealed NMR tube affords the previously reported Cp:zr(OCH=CH 2 )(H) 1b {ld) and CpRu(CO)(PMe3 )H quantitatively after 2 hours at 25 ° C. In the case of ~ the major zirconium containing CpRu(C0) 2 CH3 + C~ZrH2 12b ,__..._ 1 PMe3 * > CP2 Zr(OCH=CH 2 ) + CpRu(CO)(PMe3 )H I H lOb (15) ~ product is again g, but CpFe(CO)(PMe3 )H is only a minor component of the resulting myriad of iron complexes. A plausible mechanism for this transformation will be discussed in the following section. Treatment of CpM(CO)(PMe 3 )CH3 (M = Fe, Ru) with Cp:zrH2 appears to give products in which the metal carbonyl has been reduced, but these complexes have proven to be too unstable for proper characterization. Scheme I CpFe (CO)(PMe 3 )H lOa · CpFe (CO)(PMe 3 )D ~ l'-' 0) Cp*2 ZrH 2 +D2 > -H2 Cp*2 ZrD 2 Cp*2 ZrHD HD D2 27 Discussion ~ The reactions of bis(pentamethylcyclopentadienyl)zirconium hydrides with Group VIII transition metal carbonyls have been observed to follow two distinct pathways depending upon the natures of the reactants. Mixed-metal dimers are prepared by treating the dicarbonyls, CpM(C0) 2 (M = Co, Rh, RuH), with Cp:ZrH2 • These molecules are the first examples of metal-metal bonding between Zr and a Group VIII metal. When the metal dimer formation is prohibited by the use of zirconium monohydrides, such as C~ZrHCI, or Group VIII metal monocarbonyl or dicarbonyl alkyl complexes carbonyl reduction is observed, affording either oxycarbene complexes or products can be viewed as coming from the rearrangement of oxycarbene intermediates. The zirconium-Group VIII metal dimers, CpM(C0) 2 Zrcp: (M = Co, Rh, RuH), have similar structures consisting of a metal-metal single bond bridged by one conventionally bonded carbonyl and a CO that is bound in a linear, terminal fashion to the Group VIII metal but is also bent over in an unusual 'TT-interaction with the zirconium (a 2 .µ-,..,1, 17 bonding mode). This formulation has been confirmed by the single crystal X-ray diffraction structure determination of CpCo(C0) 2.zrcp; (see above). The µ-171, 17 2 mode of bonding for a carbonyl bridging two or more metals has been previously seen in 28 six molecules. The first such bridge was reported by Colton et al. in 1975 in the structure of M~(C0) (Ph P(CH ) PPh ) • 13 Since that time 5 2 23 22 2 TJ 1 ,TJ carbonyls have been observed in FeiC0) 13H-, 14 Cp Nb(C0) MoCp, 15 2 3 Cp2 (CH3 )Zr(CO)Mo(C0) 2 Cp, 16 Cp2 Zr(CO)(COCH3 )Mo(CO)Cp16 and Cp N'bs (CO ) , 17 the last being unique in that the CO has a ?T-interaction 3 7 with two niobiums of the triangular cluster. In each of these compounds, as well as in i and !!,, the additional electron donation from the CO rbond is needed to fill the valence electron shells of the metals. All of these molecules are also characterized by a low carbonyl stretching 2 frequency in the JR spectrum due to the 17 1 , 17 CO. i and~ join this 2 class of compounds as the first examples of an TJ 1 , 11 carbonyl bridging two significantly different metal centers. - - That 3 and 9 can also be made from the metal dicarbonyls and [Cp: ZrN2 ] 2 N2 , a ready source of coordinatively unsaturated CP.?*Zr(Il) due to the lability of the N2 ligands, suggests that pentamethylzirconocene, formed by reductive elimination of H2 from !_, could be a feasible - - - intermediate in the reaction of 1 with 2 or 8. However, the fact that cp:ZrH2 and [cp:ZrN21N2 are stable toward ligand loss in the absence - - - - of 2 or 8 under the reaction conditions at which 3 and 9 form indicates that the dicarbonyl induces the H2 or N2 elimination, possibly by an interaction between the empty zirconium la1 orbital and the oxygen lone pair of a carbonyl (Scheme II). That !. does not lose H2 in the presence of the monocarbonyl complexes, ,,...,_ 10, suggests that the second carbonyl - - of 2 and 9 may also play a role in this elimination. An alternative mechanism for the formation of H2 in the reaction of cp:ZrH2 and CpRu(C0) 2 H is by an intermolecular reductive 29 H I \\ II CpM-:?c-o, * 2~ r P2ZrH 1 I CpM(CO) + C 2 8 2 r! - - ~c-o,..;zrc~ ~ ~ *] ~ H tCpM-C=O· ' - ·-ZrC C H/ ~ 0 * Cp M (CO~ ZrC ~ +H2 M=C , o, Rh, RuH -3, 9. 0 c CpRu(CO)zB + cp~ZrH 2 S - 1 CpRu-ZrC I * I I Pz C H 0 CpRu(CO) A 2 zrCp~ 9 30 elimination of the ruthenium hydride and one of the zirconium hydrides, followed by transfer of the remaining hydride to the ruthenium (Scheme III). The H2 elimination can be viewed as an acid-base reaction between the hydridic ZrH and protic RuH and has precedence in the reaction of C~ZrH2 and CpMo(C0) 3H to give CptZr(OC-Mn(C0) 2 Cp) 2 and H • 18 2 The low activation barrier (less than 8 kcal/mole) for interchange of the carbonyls of §R between the two bonding modes is smaller than the barriers observed for the 17 1 : 77 2 carbonyl fluxionality in Cp3 Nb3 (C0) 7 19 and M~(C0) 5 (Ph 2 P(CH 2 ) 3 PPh2 ) 20 and suggests that the zirconiumcarbonyl 'lf-interactfon is fairly weak. This is supported by the reactions of ~and !!_with CO to give cp:zr(C0) 2 and CpM(C0) 2 (M = Co, RuH), which are presumably initiated by the opening of a coordination site on zirconium by the breaking of the zirconium-carbonyl 1T bond. (Scheme IV). Scheme IV co /ZrCp2* I CpM co ) 'c" II 0 (M -3,= Co,-9 Rh, RuH) -2, -8 31 The spectroscopic observation of a transient species, immediately upon mixing of CpRh(C0) 2 and C~ZrH 2 , with the spectral characteristics of a rhodium oxycarbene complex suggests that of 2 is facile, but reversible (Scheme II). The final preference for 3 addition of a zirconium hydride of 1 across the C-0 bond of a carbonyl or9 over an oxycarbene complex is probably due to the irreversibility - of H2 loss. Treatment of~ with C~ZrHX (X =Cl, F), which are much more stable to reductive loss of the hydride ligand than Cp; ZrH 2 , does not give metal-metal dimers;instead, oxycarbene complexes are isolated (eqs. 6 and 7). However, the reversible nature of the zirconium hydride addition to cobalt and rhodium carbonyls is clearly demonstrated by the equilibrium observed between CpM(C0) 2 , cp:ZrHCl and Cp(CO)M=CHO-Zr(Cl)C~ (M = Co, Rh) (eq. 6). The equilibrium ratios indicate that the cobalt or rhodium oxycarbene complexes - - are only slightly more stable than 2 and 4, even with the presence of a new Zr-0 bond worth about 120 kcal/mol. 21 The poor 1T-accepting ability of the oxycarbene ligand relative to CO is similar to that observed for other Fischer-type carbenes. 22 - Because of this, the remaining carbonyl of 5 is more electron-rich cies of~ (vco = 1947 (~, 1952 cm- (~)) compared to those of~ than those of 2 as shown by the lowering of the CO stretching frequen1 (vco = 2028, 1967 (~), 23 2051, 1987 cm- 1 (~)). 24 The increased electron density at the carbonyl of §. and the steric bulk of the decamethylzirconocene substituent on the oxycarbene should make this CO 32 less susceptible to hydriclic attack. Therefore, it is not surprising - that 5b does not react with an excess of 4 to give a bis-carbene complex. ,,...,.. Attempts to isolate or spectroscopically observe iron or ruthenium oxycarbene hydride or alkyl complexes have been thwarted by the apparent ease with which the carbene ligand reverts to the metal carbonyl and zirconium hydride or inserts into the Group VIII metal hydride or alkyl bond. The mechanism for the formation of Cp(PMe 3 )~-CH 20-Zr(H)Cp: (~ = Fe, Ru) (Scheme V) is believed to proceed through the initial -- formation of a transient oxycarbene complex, 14, which is in equili- -- brium with 15, where the carbene ligand has inserted into the M-H · bond. Trapping of the coordinatively unsaturated !§.by free PMe3 to give ,,....,... 11 is rapid, since the rate of for mati on of 11 ,,...,.. is independent of phosphine concentration. -- - That only 10 and 1 are observed in solution in the absence of PMe3 indicates that the equilibria between the starting complexes, li and .!§_,lie far toward the metal carbonyl and zi!conium hydride. These equilibria also provide a mechanism for hydride exchange between iron and zirconium that is required to explain deuterium incorporation into the hydride site of ~ from D2 in the In the case of the reaction of 1 with the iron and ruthenium methyl presence of 1. - complexes ll an intramolecular rearrangement pathway, via /3-el.i mination, is available to the coordinatively unsatured intermediate, !1, formed upon carbene insertion into the M-CH 3 bond Scheme V Cp M (CO)(PMe 3)H 10 ,...,..... l + Cp*2 ZrH2 xs PMe3• Cp M (PMe3)2 CH2 0Zr(H)Cp*2 1 g H M =Fe, Ru ~ PMe3 w w * * 1Me3 Cpr =CH-O-ZrCp2 l 41 .. 1Me3 CpM -CH20-ZrCp2 ~ 34 (Scheme VI). This step affords the zirconium-containing product, C~Zr(OCH=CH 2 )H, and CpM(CO)H which can be trapped by free PMe3 to give the observed ruthenium product, lOb, or react further to give ~ -- - the myriad of iron products seen. As in the reaction of 10 with 1 neither the oxycarbene nor inserted intermediates have been observed by spectroscopic methods. The results discussed above have shown that bis(pentamethylcyclopentadienyl}zirconium hydrides readily add to the C-0 bond of Gr,oup VIII transition metal carbonyls. However, the oxycarbene species farmed are often unobservable due to the reversibility of the hydride addition or the rapid migratory insertion of the carbene ligand into a metal hydride or alkyl bond. The spectroscopic properties of the cobalt and rhodium oxycarbene compounds that can be isolated suggest that the oxycarbene ligand is similar to those of Fischer-Type carbene complexes. Scheme VI Cp M (C0) 2 CH 3 + Cp*2 ZrH 2 - 12 1 ~ t I "*' Cp ~ =C-o-1rCp2 CH 3 M =Fe, Ru Cp~ z( 'cH=CH2 + [M] 13 0 CO H I .. 0 H H l ,8-elim c HI I * - 'CpM-9-o-1rCp2 CH3 H ~ CJ') Table I. NMRa and IRb data. Compound IR 1u NMR CpCo(C0) 2 ZrC~ (~) v(CO) 1737, 1683 Cs!!s Cs(C!!s)s 4. 91 s 1. 71 s CpRh(C0)2Zrcp: (~) v(CO) 1752, 1696 Cs!!s Cs(C!b)s 5.40 s 1. 76 s Cp(CO)Co=CHO-Zr(Cl)Cp: (~ v(CO) 1947 Co=CHO-Zr 12. 6 s 5. 48 s 1. 82 s Cs!!s Cs(C!!s)s Cp(CO)Rh=CHO-Zr(Cl)Cp: (~ v(CO) 1952 Rh=CHO-Zr - Cs!!s Cs(C!!s)s Cp(CO)Co=CHO-Zr(F)CP2* (~) v(CO) 1948 Co=CHO-Zr Cs!!s Cs(CHs)s Cp(CO)Rh=CHO-Zr(F)C~ (_Th)c v(CO) 1956 Rh=CHO-Zr Csff.s Cs(C!b)s Cp(H)Ru(C0) 2 ZrCp2* (!!) v(CO) 1706, 1671 . Cs!!s Cs(Cffa)s Cs(C!b)s RuH 13.1 s 4. 94 s 1.87 s 12. 6 s 4. 87 s 1. 80 s 13.l s 5.41 s 1. 80 s 5.17 s 1.67 s 1. 74 s -15. 7 s ~ 0) Table I (continued) Compound Cp(PMe 3 ) 2 Fe-CH 20-Zr(H)Cp2* (_!!~) IR 1 H NMR Fe-C!bO-Zr C5ffs C5(C!b)5 P(C!b) 3 ZrH Cp(PMe 3 ) 2 Ru-CH 20-Zr(H)C~ (fil) Ru-C!bO-Zr C5H5 C5(C!b) P(C!!_a) 3 ZrH 5.07 t 3.87 t 2.07 s 1.04 t 5.25 s 5. 32 dd 4.99 s 2.09 s 1.11 m 5.22 s 3 3 2 3 JPH = 7 JPH = 2 JPH = 3 JPH = 7' 9 a) NMR spectra in benzene-~ or toluene-~ at 34 ° C at 90 MHz. Chemical shifts in o measured from internal TMS, coupling constants in Hz. b) IR spectra recorded as nujol mulls. Values given in cm - i . Detailed spectra are listed in the experimental section. c) IR spectrum in C 6H6 • CA> -:J 38 Table II. Data Collection and Refinement Conditions for Formula C27H 35 Co02 Zr Formula weight 541. 73 g/mol Space group P2 1 /c a 15. 624(6) .A b 13. 885(13) A c 11. 221(4) A. f3 94. 01(3). v 2424. 7(1. o) .A z 4 Peale Crystal size 1. 49 g/cm- 3 O. 5 x O. 4 x O. 2 mm µ 0. 71069 A (MoKa, graphite monochromator) 1. 95 cm- 1 Scan range 0. 75 ° in 29 below K ll1 0. 75 e in 29 above K a2 29 limits 2.5-65° Scan rat~ 1.2°/min Bkgrd time/scan time 0.7 Total number of averaged data 8824 Refinement on 39 Table III, Part A. Atomic Positions and Gaussian Amplitudes of Non-Hydrogen Atoms. Atom X* y z Ui1 u22 u33 U12 U13 U23 Zr '14565( 3) 48394( (4) 32578( 2) MO( 2) 334( 2) 246( 2) -'7( 3) 19( 2) 12( 2) Co '76280( 5) 46318( 6) 458( 5) 429( 5) 263( 3) 20( 4) 57( 2) 18( 3) 01 '14422(35) 31946(35) 25153(45) 470(33) 464(31) -8(27) 41(26) '10(26) 02 '16807(41) 66470(40) 14429(46) 777(45) 394(34) 435(33) -36(32) 46(31) 42(26) Cl C2 C3 C4 8909( 6) 75203(56) 37708(53) 17328(68) 382(31) 375(40) 439(46) 353(42) 8(43) 46(35) -20(39) 89(39) '16224(54) 58335(54) 17272(67) 438(48) 389(46) 388(42) 18(42) 66(42) 76628(52) 39250(51) 90596(52) 939(61) 887(50) 329(43) 51(45) 140(37) -110(33) 69831(50) 45938(54) 89792(51) 864(57) '190(56) 317(32) -80(46) -37(34) -54(34) cs 73462(59) 54964(52) 91936(52) 1207(69) 691(50) 285(31) 385(51) 60(39) 135(32) C6 82310(54) 53790(56) 93762(55) 976(61) 820(60) 365(35) -217(50) 190(38) 8(37} C7 84215(45) 44252(54) 92874(54) 590(43) 824(53) 425(37) 16(42) 192(33) -16(36} ca 58605(34) 45301(46} 27634(53) 252(29) 587(42) 54 9(38} -59(29) C9 59727(37) 55451(46) 27289(53) 319(33) 599(41) 471(37) 101(31) 56(29) ClO 62245(36) 58594(44) 38825(57) 260(32) 482(39) 671(43) 37(29) 99(31) -126(33) cu 62501(33) 50422(50) 46476(46) 270(27) '176(48) 383(48) 58(32) '16(23) -41(32) C12 60550(37) 42340(46) 39490(58) 314(32) 518(42) 679(44) -'1(30) 183(31) 119(34) C13 54864(45) 39327(62) 17468(71) 379(40) 1196(73) 950(59) -56(45) -168(40) -501(53) C14 56929(48) 61788(67) 16804(75) 488(48) 1260(79) 1026(66) 249(50) C15 63294(50) 69025(54) 42291(83) 529(50) C16 62584(45) 50211(70} 59860(55) 512(41} 1 '164(90) Cl 7 59440(50) 32212(59) 43982(86} -4(48} 72(31) 437(59} 95(42} 17(52) -329(51) 92(57) 97(30) -23(51} 522(49) '187(59} 1546(84) -109(44} 355(44} 396(57) C18 90891(34} 51732(47} 33217(48} 272(27) 688(42) 420(30} -82(32) 27(23} 9(33} C19 87244(37) 58489(43) 40675(50) H3(34) 489(39) 434(34) -106(30) -95(28) 11(29) C20 84232(34) 53510(41) 50478(44) 309(28) 525(41) 326(28) -53(28) -16(23) -63(27) C21 85483(35) 43575(43) 48852(47) 304(31) 507(37) 372(31) -20(29) -'15(26) 116(27) C22 89703(36) 42356(43) 38149(53) 265(31) 433(38) 597(39) 46(28) -63(29) -72(31) C23 96005(41) 53777(55) 22657(61) 395(35) 982(61) 672(43) -113(40) 171(33} '10(42) C24 88007(46) 69314(49) 39677(62) 605(46) 554(45) '108(47) -193(37) -195(38) 94(36) C25 82076(45) 58410(53) 61944(56) 555(44) 823(54) C26 83890(47) 35624(51) 57716(61) 833(49) 671(50) 494(39) -79(41) -89(34) -126(37} 631(45) ;.:68(41) -150(39) 175(38) C2'7 93148(42) 33060(53) 33646(67) 414(41) 624(52) 1426(79) 22(27) -130(31) 405(35) '108(51) 899(56) 131(38) -59(40) -85(42) Final Scale Factor a: O. 9158(20) Final Secondary Extinction Factor • O. 0692(181) z 10·6 •Positional para.meters z 105, thermal parameters z 104; the form of the thermal ellipsoid 2 2 2 1a expl-2n- {h a• u 11 + • • • + 2klb*c•u23 >). 40 Table IlI, Part B. Atomic Positions (x 104 ) for Hydrogen Atoms. Atom x y z Atom x y z H3 7623 3265 8961 H171 5457 2930 4010 H4 6405 4468 8830 H172 6512 2886 4325 HS 7078 6097 9203 H173 5862 3299 5331 H6 8672 5870 9573 H231 9431 4789 1650 H7 8992 4152 9353 H232 9530 6029 2032 H131 4912 3675 1977 H233 245 5184 2560 Hl32 5396 4331 1064 H241 8255 7202 3728 H133 5890 3387 1636 H242 9106 7164 4850 H141 5080 6135 1541 H243 9245 7051 3280 H142 5915 6798 1827 H251 7747 6350 5961 H143 5967 5879 968 H252 8029 5365 6736 H151 5814 7264 3950 H253 8751 6211 6487 H152 6547 6992 4996 H261 8153 3857 6502 Hl53 6812 7331 3638 H262 8068 3062 5370 H161 5678 5092 6237 H263 9023 3297 6038 Hl62 6597 4479 6355 H271 8883 2828 3332 H163 6587 5687 6271 H272 9598 3438 2603 H273 9837 3100 3990 B* = 7. 00 for all hydrogens. * Thermal parameters are of the form exp(-B((sin29)/A2)). 41 Table IV. Bond Distances (A) in CpCo(C0} 2 ZrC~. Zr-Co Zr-C1 Zr-01 Co-C1 Co-01 C1-01 Zr-C2 Zr-02 Co-C2 Co-02 C2-02 Co-C3 Co-C4 Co-C5 Co-C6 Co-C7 C3-C4 C4-C5 C5-C6 C6-C7 C7-C3 Co-Cp* Zr-CS Zr-C9 Zr-010 Zr-C 11 Zr-C12 C8-C9 C9-C 10 2.926(1 2.272(8 2.431(5 1.68~· (8 2.888(5 1.200(9 2.233(8 3.266(6) 2.034(8) 2.922(6) 1.179(10) 2.081(7) 2.106(7l 2.087(7 2.082(7 2.091(7 1. 409 ( 1 o~ 1.390(10 1.393(10 1.363(10) 1.382(10) 1. 725~7) 2.553 6) 2.54R 6~ 2.528(6 2.545(6 2.518(6~ 1.421(8 1.396(8 C10-C 11 C11-C 12 C12-CS CS-C 13 C9-C 14 C10-C15 C11-C 16 C12-C17 Zr-Cp*1* Zr-C18 Zr-C19 Zr-C20 Zr-C21 Zr-C22 C18-C19 C19-C20 C20-C21 C21-C 22 C22-C 18 C18-C23 C19-C24 C20-C25 C21-C26 C22-C27 Zr-Cp*2* 1.422(B) 1. 390 ( R) 1.405(R) 1.496(10) 1.50Q(10) 1.506(10) 1. 501 ( 9) 1.508(11) 2.238(6) 2.589(6) 2.542(6l 2.529(5 2.501(6 2.546~6 1. 404 8) 1. 408 8~ 1.407(8 1.420(8 1.432(8) 1.502(9) 1.513~9) 1.514 9) 1.518 9) 1. 500 ( 9) 2.239(6) *Cp = C3-C7 ring centroid, Cp*1 = C8-C12 ring centroid, Cp*2 = C18-C22 ring centroid. 42 Table V. Bond angles (deg) in CpCo(C0) 2 ZrC~. Zr-C1-G1 Co-C 1-01 Zr-C 1-Co Zr-Co-C 1 Co-Zr-C1 Co-Zr-01 Zr-C2-02 Co-C2-02 Zr-C2-Co Zr-Co-C2 Co-Zr-C2 Zr-Co-Cp Co-Zr-Cp*1 Co-Zr-Cp*2 Cp*1-Zr-Cp*2 C3-C4-C5 C4-C5-C6 C5-C6-C7 C6-C7-C3 C7-C3-C4 C8-C9-C 10 C9-C 10-C 11 C 1 0-C 11 -C 1 2 C 11-C 12-C8 C 12-C8-C9 82. 7 ( 5) 176.7(7) 94.1(3) 50.8(3) 35.2(2~ 64.5(1 144.7(6 128.9(6) 86.4{3 4Q.6(2 44.0(2 168.2(5 109.5~5 110.2 5 ~6g:~~~l6 108.0 108.8 7 108.2(6 108. 3( 6) 108.2(5) 107.7(5) 107.9(5) 108.8(5) 107.3(5) C9-C8-C 13 C 12-C8-C 13 C8-C9-C 14 C 10-C9-C 14 C9-C 10-C 15 C 11-C 1 0-C 1 5 C 10-C 11-C 1 6 C 1 2-C 11-C 1 6 C11-C 12-C 17 C8-C12-C17 C 18-C 19-C 20 C19-C20-C21 C20-C 21-C 22 C21-C 2 2-C 18 C2 2-C 18-C 19 C 19-C 18-C23 C22-C 18-C 23 C 18-C 19-C24 C20-C 19-C 24 C 19-C 20-C 25 C 2 1-C 20-C 2 5 C20-C 21-C 26 C22-C 21-C 26 C21-C22-C27 C 18-C 22-C 27 124.8(6) 127. 4( 6) 124. 7 ( 6) 12h.0(6) 124.0(6) 127. 9( 6) 128. 1 ( 6) 122.3(6) 126.2(6) 124.5(6 108.0(5 108.9(5 107.7(5 107.4(5 108.0~5 127. 2 5) 124.6 5) 125.6(5) 125.3(5) 123.3(5) 126.3(5) 126.7(5) 125.1(5) 125.9(5) 126.4(5) 43 Table VI. Least-Squares Planes. Metal-Carbonyl Substructure Atom Zr Co Cl C2 01 02 Cp Cp*l Cp*2 Deviation from Plane (A) O. 0101(5) O. 0097(7) -0.0013(78) -0. 0055(78) -0.0086(51) -0.0044(56) 0.0283 2.1170 -2.0754 Cp Ring Atom C3 C4 C5 Co C7 Deviation from Plane (A) O. 0081(69) -0.0078(70) O. 0046(74) 0. 0004(74) -0. 0054(68) Cp*l Ring Atom Deviation from Plane (A) ca o. 0080(58) C9 ClO Cll C12 O. 0026(60) -0.0120(60) O. 0171(57) -0. 0157(62) Cp*2 Ring Atom Cl8 Cl9 C20 C21 C22 Deviation from Plane (A) O. 0132(56) -0. 0195(57) O. 0182(53) -0. 0098(55) -0. 0021(58) 44 ~ General Considerations. All manipulations were performed under an inert atmosphere by employing a nitrogen-filled glove box and vacuum-line techniques. Hydrogen, deuterium, nitrogen and argon were purified by passing through MnO on vermiculate 25 and activated 4 A molecular sieves. Benzene, toluene and pet ether (30"-60°), including NMR solvents, were vacuum transferred from LiAlH or molecular sieves, then from "titanocene" 26 prior to .u se 4 Carbon monoxide (MCB), 13 C carbon monoxide (Monsanto-Mound) and PMe3 (strem) were used as received; NHMe 2 was vacuum transferred from 4A molecular sieves. 23 24 27 28 CpCo(C0) 2 , CpRh(C0) 2 , CpFe(C0) 2 CH 3 , CpRu(C0) 2 CH 3 , 30 29 CpRu(C0) 2H, · CpFe(CO)(PMe3 )H, were prepared by literature methods. CpFe(CO)(PMe3 )CH3 was made by treatment of CpFe(CO)(PMe 3 )H with CC14 followed by CH 3 MgBr and isolated by sublimation. CpRu(CO)(PMe 3 )H was made by a variation of the 29 13 reported synthesis of CpRu(CO)(PPhs)H. CO enrichment of the 13 carbonyls of CpRh(C0) 2 was done by photolysis under a CO atmos31 phere. cp:ZrH 2 2 and [cp:ZrN2 l 2 N2 were prepared by literature methods. Conproportionation of Cp:zrH 2 and Cp:zrX 2 (X = F, Cl) at 150" C for 2 weeks under an H2 atmosphere affords cp:ZrHX in excellent yield. 1 H NMR spectra were recorded in C 6 D6 or C7 D8 with TMS as an internal reference using Varian EM-390, JOEL FX90Q and Bruker WM-500 spectrometers. 13 and Bruker instruments. m spectra were recorded as IR mulls or C NMR spectra were recorded on the JOEL 45 benzene solutions on a Beckmann IR H240 spectrophotomer. Elemental analyses were performed by Alfred Bernhardt Analytical Laboratory and Dornis and Kolbe Microanalytical Laboratory. Procedures: CpCo(C0) 2 ZrCp: (~). A 0. 75 M toluene solution of CpCo(C0) 2 (950 µl, 0. 714 mmol) was added via syringe to cp;zrH 2 (250 mg, 0. 689 mmol} dissolved in 30 ml pet ether at -78 ° C. On warming to room temperature and stirring for 3 hours the reaction solution turned dark green. The solution was concentrated to ca. 3 ml and filtered to afford dark green, crystalline CpCo(C0} 2 Zrcp: (1 70 mg, 46%) which was washed with cold pet ether and dried in vacuo to remove excess CpCo(C0) 2 • 0. 83 equivalents of H2 per equivalent of cp;zrH2 were recovered through a Toepler pump at the completion of the reaction. In an alternative synthesis, neat CpCo(C0) 2 (175 µl, 1. 36 mmol} was added to a pet ether solution of [cp:ZrN2 l 2 N2 (500 mg, 0. 62 mmol) via syringe at -78" C. Similar work-up .as before afforded 3a (500 mg, """'"'" 74%) as dark green-black crystals. Anal. Calcd. for C27 H35 Co02 Zr: C, 59.86; H, 6.51; Co, 10.88; 0, 5.91; Zr, 16.84. Found: C, 59.98; H, 6.62; Co, 10.91; 0, 5.74; Zr, 17.01. IR (nujol mull}: 1737 vs, tube was placed under 65 0 Torr CO at -78 °, sealed, warmed to room temperature and then to 80° C to effect reaction. ·structure Determination for CpCo(C0) 2 ZrCp:. A single crystal of ~ was mounted in ~.glass capillary under N2 • Rotation arid Weisenberg photographs (using CuKa radiation) indicated a monoclinic 46 lattice with systematic absences in the a* and c* axes (hOl, 1 = 2n + 1) consistent with the space group P 21 /c. Observation of systematic absences along the b* axis (OkO, k = 2n+ 1) on the diffractometer confirmed this assignment. The crystal was mounted with its long axis (b) slightly skew to the q; axis of a locally modified Syntex P2 1 diffractometer; details on unit cell parameters and data collection are given in Table II. The intensities of four check reflections were monitored every 100 reflections and showed a small (2%) decrease over the course of the data collection. A fifth check reflection, the 415, had a significant (25%) decrease in intensity during the last fourth of the data set, when reflections were being measured at high 2e angles in the hkl octant. Examination of peak profiles indicated that this intensity loss was due to improper centering of the diffractometer on the check reflection, rather than crystal movement or decomposition. Measurement of the intensity of this reflection outside the scan sequence remained consistent with the other four reflections. An averaged data set of 8824 reflection intensities was assembled from the collected data after deletion of duplications and systematic absences. The data set was placed on an absolute scale by means of a Wilson plot using scattering factors for Zr and Co calculated from Cromer and Mann32 and for C, H and 0 from Cromer and Waber. 33 No absorption correction was applied. ·The locations of the two metal atoms were determined from a three-dimensional Patterson map. A structure factors computation using these positions gave an R index (:6 I F0 l -1 Fc I I I; IF 0 I) of 0. 367. 47 Generation of a Fourier map led to the locating of all non-hydrogen atoms which were then placed into the structure· factors program in two stages, yielding mR index of O. 314. Several cycles of leastsquares refinement, minimizing ~w[~-(Fc/k} 2 ] , interspaced by 2 Fourier and difference Fourier syntheses, led to; an R factor of 0.15~~­ using isotopic thermal parameters for all atoms. At this point aniso. tropic thermal parameters were introduced in two least-squares cycles, initially for the two metals and then for all other non-. hydrogens, yielding m0.130 R index. A least-squares cycle refining the temperature parameters of all atoms, followed by two cycles refining metal p:trameters and the scale factor gave a R factor of 0.125. Examination of the structure factors showed that significant noise was being introduced into the calculation by the low intensity data. It was determined that the R index for the 3843 data with F~ ~ 3a (F~) was approximately 0. 065 compared to 0.125 for all data. The calculation was the;refore continued using only the higher intensity data. A secondary extinction coefficient of O. 05 was also introduced. 34 At this point a difference Fourier map was generated in the plane of the Cp ring and the five hydrogens were tentatively located. Planes were also generated perpendicular to the ring carbon-methyl carbon axes of the Cp* rings at a distance of O. 30A from each methyl carbon and these hydrogens were placed at 0. 92A from each carbon. All hydrogens were given an arbitrary isotopic temperature factor of 7. 00, about 1. 00 greater than that of the carbon to which they were attached. Addition of the hydrogen atoms and several least-squares cycles refining the non-hydrogen atoms, scale factor and secondary extinction 48 coefficient in varyingly blocked matrices, gave an R factor of O. 063. Re-positioning the hydrogens as above and three additional cycles gave 1 2 a final R factor of 0. 056 with a goodness of fit ([I; w(~ -s F~) /(n-p)] 2, w = 1/a 2 (F~), 1/s = scale factor for F 0 , n =total number of reflections, p =total number of parameters) of 1. 94 for 3842 reflections with F 0 ~ 3a (F 0 ) giving a data-to-parameter ratio of 13. 7. A structure factors calculation using all data gave an R index of 0.120. CpRh(C0) 2 Zrcp: (_filV. Pet ether solutions of cp:ZrH 2 (500 mg, 1. 38 mmol) and CpRh(C0) 2 (200 µl, 375 mg, 1. 67 mmol) were combined at -78" C, warmed, and stirred at room temperature for 20 minutes. After this time all solvent and excess CpRh(C0) 2 were removed in vacuo. CpRh(C0) 2 Zr cp: (510 mg, 44%) was recrystallized from toluene. IR (nujol mull): 1752 vs, 1696 vs, 1027 w, 780 s, 650 m. Addition of CpRh(C0) 2 (ca. 10 µL, ca. O. 08 mmol)) to a C6 D6 solution of [ cp; ZrN2 ] 2 N2 (30 mg, O. 04 mmol) in an NMR tube g"ave an 1 H NMR spectrum identical to that of~ prepared from Cp:ZrH 2 • The IR spectrum of the C 6 D6 solution was also the same as that of ~ prepared by the above procedure. Variable Temperature 13 C NMR of CpRu(CO) ZrCp*. Substitution of CpRh(1 3 C0) 2 for CpRh(C0) 2 in the above procedure allowed the preparation of ?'P enriched with temperature 13 13 C at the carbonyl carbons. Variable C NMR spectra at 22. 5 MHz yielded the coalescence temperature and a spectrum at -70c C at 125. 8 MHz provided an approximate chemical shift difference of the resonances of the inequivalent carbonyl carbons in the low temperature limit. Use of the Gutowsky-Holm approximation 35 allowed the calculation of an upper 49 limit for the barrier to carbonyl interchange. Cp(CO)Co=CHO-Zr(Cl)Cp; (§_~). Toluene solutions of cp;zrHCl (400 mg, 1. 01 mmol) and CpCo(C0) 2 (150 µ1, 220 mg, 1. 20 mmol) were mixed at -78"C, then warmed to 25c C with stirring for 2 hours to effect reaction. Concentration to ca. 2 ml and addition of 10 ml pet ether afforded red crystals which were isolated by filtration, washed with cold pet ether and dried to give Cp(CO)Co=CHO-Zr(Cl)Cp; (260 mg, 45%). Anal. Calcd. for C27 H36C1Co02 Zr: C, 56. 09; H, 6. 28; Cl, 6.13. Found: C, 51.87; H, 5. 96; Cl, 5. 74. m (nujol mull): 1947 vs, 1350 m, 1308 m, 1295 vs, 1165 w, 1110 w, 1020 w, 802 m, 670 w, 532 w, 495 m. Cp(CO)Rh=CHO-Zr(Cl)Cp: (~). Treatment of CpRh(C0) 2 ( 200 µl, 1. 67 mmol) instead of CpCo(C0) 2 with cp;zrHCI (600 mg, 1. 51 mmol) by the above procedure afforded ,,.....,..._ 5b (720 mg, 78%) as golden crystals. Anal. Calcd. for C27H36Cl02 RhZr: C, 52.12; H, 5. 83; Cl, 5. 70. Found: C, 51. 95; H, 6. 04; Cl, 5. 78. m (nujol mull): 1952 vs, 1353 s, 1308 m, 1015 w, 783 m, 712 w, 650 w. Cp(CO)Co=CHO-Zr(F)Cp; (~. Treatment of CpCo(C0) 2 (165 mg, 150 µl, O. 94 mmol) with cp;zrHF (300 mg, O. 83 mmol) by the method used for 5a afforded 7a (260 mg, 57%) as orange crystals. """"' """"' IR (nujol mull): 1948 vs, 1350 m, 1300 vs, 1167 w, 1111 w, 1021 w, 801 m, 670 w, 614 w, 538 m, 498 m. Cp(CO)Rh=CHO-Zr(F)Cp2* (Th). CpRh(C0) 2 (15 µI, 0.12 mmol) was added to a C 6 D6 solution of cp;zrHF (30 mg, O. 08 mmol) in a . NMR tube at 25" C. Cp(CO)Rh==CHO-Zr(F)Cp: was identified by its 1H NMR and m spectra. IR (C 6H6 solution): 1953 vs, 1382 m, 1304s, 1166 w, 1008 w, 792 w. 50 HCl (0. 05 mmol) was condensed onto a C7 D8 solution of~ (25 mg, O. 05 mmol) at -196• C in an NMR tube, which was then sealed and warmed to room temperature. 1 The reaction was fallowed by H NMR spectroscopy. Cp(H)Ru(C0) 2 ZrC~ (!!.). CpRu(CO)Jf was prepared using the procedure of Humphries and Knox 29 by reflux of RtJs(C0) 12 (250 mg, O. 39 mmol) and cyclopentadiene (ca. 3 ml, ca. 36 mmol) in 60 ml heptane for li hour. C~ZrH2 (405 mg, 1.12 mmol) was added to this reaction mixture at 25 • C causing the solution to turn red over 10 minutes. Concentration to ca. 5 ml and cooling to -78 • C precipitated the product which was isolated by filtration and washed with cold pet ether giving Cp(H)Ru(C0) 2 ZrC~ (380 mg, 59%) as brick red crystals. Alternatively, ~was prepared from RtJs(C0) 12 (170 mg, 0.27 mmol), CpH (ca. 3 ml, aa. 36 mmol) and [C~ZrN2 ] 2 N2 (290 mg, O. 36 mmol) using a sin?.ilar procedure. In this case all gas liberated during the course of the reaction was collected through a Toepler pump. The H NMR and m spectra of!!_ prepared from [C~ZrN2 ] 2 N2 1 were identical to those of !!_made from C~ZrH 2 • Anal. Calcd. for C27H360 2 RuZr: C, 55. 45; H, 6. 20; Ru, 17. 28. Found: C, 55. 09; H, 6. 03; Ru, 17. 50. m (nujol mull): 1706 vs, 1671 vs, 1021 m, 831 w, 794 m, 718 m, 668 m • .,.._,._~~..,...,,...~""""""""""".....:::*~+-C""O.......-.o A C 6 D6 solution of !!_ (2 7 mg, O. 05 mmol) was placed under 700 Torr CO at -78• C tube, sealed, and warmed to room temperature. in an NMR 51 Cp(PMe3 ) 2 Fe-CH 20-Zr(H)Cp2* (lli). Toluene (15 ml) and PMe 3 (Oo 49 mmol) were added to a mixture of CpFe(CO)(PMe 3 )H (90 mg, O. 40 mmol) and cp;ZrH 2 (135 mg, O. 37 mmol) at -196 • C. On · warming to room temperature for 2 hours red crystals formed. Concentration to ca. 2 ml, filtration and washing with cold pet ether afforded Cp(PMe 3 ) 2 Fe-CH 20-Zr(H)Cp: (125 mg, 51%). Anal. Calcd. for C32H56 Fe0P2 Zr: C, 57.73; H, 8.48; P, 9.30. Found: C, 57.88; H, 8.10; P, 9.30. Cp(PMe3 ) 2Ru-CH 2 0-Zr(H)Cp: (llb). C 6D6 and PMe 3 (0. 08 or O. 68 mmol) were added to a mixture of CpRu(CO)(PMe 3 )H (20 mg, O. 07 mmol) and cp:ZrH2 (25 mg, O. 07 mmol) at -196° C in an NMR tube. The tube was seale.d, warmed to room temperature and the reaction monitored by NMR spectroscopy. Cp(PMe3 ) 2 Ru-CH 20-Zr(H)Cp: was identified by the similarity of its 1H NMR spectrum to that of 1 la. ~ CpFe(C0) 2 CH3 + cp:ZrH 2 • NMR samples of ! (50 mg, 0.14 mmol) and~ (30 mg, 0 ..15 mmol) were prepared in C7 D8 with and without PMe3 (0. 25 mmol) at -196e C. After sealing the samples were warmed to -78° C to liquify the solvent, then to 25 ° C. The reactions were monitored by 1H NMR spectroscopy the products being identified by comparison to previously reported spectra. CpRu(C0) 2 CH3 + Cp:ZrH 2 • A similar procedure to that above - was employed using 1 (30 mg, O. 08 mmol)~ 12b (20 mg, O. 08 mmol) and PMe 3 (0.10 mmol). ~ 52 References ~ 1.. (a) Wolczanski, P. T.; Threlkel, R. S.; Bercaw, J. E. J. Amer. Chem. Soc. "'-""-"" 101, 218 (1979); (b) Threlkel, R. S.; Bercaw, J. E. J. Amer. Chem. Soc. W, 2650 (1981). 2. Manriquez, J. M.;McAlister, D.R.; Sanner, R.D.;Bercaw, J. E. J. Amer. Chem. Soc. 100, 2716 (1978). ~ 3. -- (a) Mango, F. D. ; Dvoretzky, I. J. Amer. Chem. Soc. 88, 2654 (1966); (b) Empsall, H. D.; Hyde, E. M.; Markham, M.; McDonald, W. S.; Norton, M. C.; Shaw, B. L.; Weeks, B. J. Chem. Soc., Chem. Commum., 589 (1977). 4. Barger, P. T.; Bercaw, J. E. J. Organomet. Chem. ~' C39 (1980). 5. Sanner, R. D.; Manriquez, J. M.; Marsh, R. E.; Bercaw, J. E. -- J. Amer. Chem. Soc. 98, 8351 (1976). 6. Rattinger, E.; Muller, R.; Vahrenkamp, H. Angew. Chem. Int. Ed. Engl. li_, 332 (1977). 7. Wong, K. S.; Scheidt, W. R.; Labinger, J. A. Inorg. Chem. U, 1709 (1979). 8. Guggenberger, L. J.; Meakin, P.; Tebbe, F. N. J. Amer. Chem. 9. Soc. 96, 5420 (1976). Dahan, F.; Jeannin, Y. J. Organomet. Chem. W, 25 (1977). 1 O. Fachinetti, G. ; Fochi, G. ; Floriani, C. J. Chem. Soc. , Dalton -- Trans., 1946 (1977). 53 11. (a) Connor, J. A.; F.iS!her, E. 0. J. Chem. Soc. A, 578 (1969). (b) Fischer, E. 0.; Kollmeier, H. -J., Chem. Ber. 104, 1339 ~ (1971). 89, 7141 (c) Klabunde, U.; Fischer, E. O. J. Amer. Chem. Soc. ,,.._,-.. (1967). 12. (a) Erwin, D. K.; Ph.D. Thesis, California Institute of Technology, 1979. (b) Bercaw, J. E. Adv. Chem. Ser. N . 167, 136 (1978). 13. Colton, R.; Commons, C. J.; Haskins, B. F. J. Chem. Soc., Chem. Commun., 363 (1975). 14. Manassero, M.; Sansoni, M.; Langoni, G. J. Chem. Soc., Chem. Commun., 919 (1976). 15. Pasynskii, A. ; Skripkin, Y. ; Eremenkov, I. L. ; Kalinnikov, V. ; A leksandrov, G. ; Andrianov, V. G. ; Struchkov, Y. J. Organo- met. Chem. 165, 49 (1979). ~ 16. (a) Longato, B.; Norton, J. R.; Huffman, J.C.; Marsella, J. A.; Caulton, K . G. J. Amer. Chem. Soc. 103, 209 (1981). ~ (b) Marsella, J. A.; Huffman, J. C.; Caulton, K. G.; Longato, B.; Norton, J .. R. J. Amer. Chem. Soc. 104, 6360 (1982). ---------~ 17. Herrmann, W. A.; Ziegler, M. L.; Weidenhammer, K.; Biersack, H. Angew. Chem. Int. Ed. Engl. U, 960 (1979). 18. Berry, D. H.; Bercaw, J. E., manuscript in preparation. 19. Lewis, L. N.; Caulton, K. G. Inorg. Chem. li, 3201 (1980). 21. Connor, J. A. Topics in Current Chemistry 11., 72 (1977). 20. Marsella, J. A.; Caulton, K. G. Organometallics 1, 274 (1982). 22. Brown, F. J. Prog. Inorg. Chem. ll, 1 (1980). 54 23. Piper, T. S.; Cotton, F. A.; Wilkinson, G. J. Inorg. Nucl. Chem. 1, 165 (1955). -""' 24. Fischer, E. 0.; Bittler, K. Z. Naturforsch. ,,...,,.._ 16b, 225 (1961). 25. Brown~ T. L.; Dickerhoof, D. W.;Bafus, D. A.;Morgan, G. L. Rev. Sci. Instrum. -""'-""' 33, 491 (1962). 26. Marvich, R. H.; Brintzinger, H. H. J. Amer. Chem. Soc. -""'-""' 93, 2046 (1971). 27. Piper, T. S.; Wilkinson, G. J. Inorg. Nucl. Chem. ~' 104 (1956). 28. Davison, A.; McCleverty, J. A.; Wilkison, G. J. Chem. Soc., 1133 (1963). 29. Humphries, A. P.; Knox, S. A. R. J. Chem. Soc., Dalton Trans. 1710 (1975). 30. Kalck, P.; Poilblanc, R. C. R. Acad. Sc. Paris C ~ 66 (19r72). 31. Manriquez, J. M.; Bercaw, J. E. J. Amer. Chem. Soc. ,,...,.. 96, 6229 (1974). ™' 32. Cromer, D. T.; Mann, B. Acta Cryst. 33. Cromer, D. T.; Waber, J. T. Acta Cryst. ~' 104 (1965). 34. Larson, A. C. Acta Cryst. ~' 664 (1967). 35. Gutowsky, H. S.; Holm, C. H. J. Chem. Phys. ~' 1228 (1956). 321 (1968). 55 CHAPTER II Synthesis and Reactivity of Some Zirconium Oxycarbene Complexes 56 Introduction ~ Bis(pentamethylcyclopentadienyl) zirconium hydrides have proven to be useful reagents for the reduction of transition metal bound carbon monoxide. l, 2, 3 Previous work has demonstrated that these hydrides, in particular cp:ZrH2 , can add across the carbon-oxygen bond of a carbonyl on a variety of metals to afford a zirconoxy carbene product. (1) 3 By this method oxycarbene complexes of niobium, 2 chromium, molybdenum, 3 tungsten, 3 cobalt 4 and rhodium4 have been prepared; C~ZrH 2 also appears to add readily to iron and ruthenium carbonyls, 4 but the carbenes prepared have proven unstable toward further rearrangement. The first evidence that C~ZrH 2 could reduce carbon monoxide bound to zirconium was the preparation of cis-(C~ZrH) 2 (µ-0CH=CHO-) 1 .by the treatment of C~Zr(C0) 2 with cp:ZrH 2 under an H2 atmosphere, ' 3 (2) the proposed mechanism 1d of which is shown in Scheme I. We have examined this mechanism in more detail by the syntheses of molecules similar to the unisolable intermediates invoked in Scheme I. The initial step of Scheme I is the formation of a zirconium oxycarbene intermediate, similar to those isolated for Group V and VI 57 Scheme I /co Cp~Zr(C0)2 + Cp~ZrH 2 -~• Cp~Z, C-OZrCp~ I H l /0 Cp~Zr I 'c ~·- 'c-ozrcp~ I I H H CH=CH I Cp~Zr/0 'H °' \ ZrCp~ H/ I H 58 transition metals. Without H2 , Cp:zr(C0) 2 and Cp:ZrH2 give a myriad of products, the first of which is a transient species exhibiting 1 the down-field resonance in the H NMR spectrum expected for the proton on an oxycarbene ligand. 5 The instability of the intermediate is presumably due to two factors; the unfavorable steric interaction of the two bulky decamethylzirconocene fragments in contact due to the two-atom zirconoxy carbene bridge, and the presence of a carbonyl ligand, which may lead to alternate pathways of rearrangement. In our effort to prepare stable zirconium oxycarbene complexes we have tried to minimize these factors. The only previous reports of zirconium carbene complexes have been by Schwartz and co-workers. In 1980 the spectroscopic observation of Cp2 Zr(CH 2 )(PPh 2 Me) was reported, though isolation of the (3) product was prevented by its instability at room temperature under the reaction conditions. 6 Recently, this group has reported the isolation of Cp2 (L)Zr=C(H)(CH 2 R) (L = PPh3 , PMe 2 Ph; R = t-Bu, C6 H11' CH (Me )(Et)) as impure oils. 7 The second step proposed in Scheme I, an intramolecular coupling of the carbene and carbonyl ligands to give a metal ketene intermediate, has very little precedence in the chemical literature and the ref ore also warranted further study. The use of transition metals to catalyze the formation of new C -C bonds is an important part of 59 industrial processes which use CO as a feedstock for products with more than one carbon atom. Commonly invoked mechanisms for metal catalyzed C-C bond making include carbonyl insertion8 (hydroformylation) or olefin insertion into metal alkyl bonds 9 (Ziegler-Natta olefin .polymerization - Cossee mechanism) and oligomerization of carbenes on metal surface to give linear hydrocarbons 1O ( Fischer-Tropsch catalysis). However, the possibility of carbene-carbonyl coupling to give new C-C bonds has not received much attention. In 1960 Schrauzer and Rilchardt reported that in the presence of Ni(C0) 4 diazomethanes give products, presumably arising from a nickel carbene intermediate that releases the substituted ketene {which was trapped with ethanol) upon decomposition. 11 Carbonylation of (C0) 5 Cr=C(OMe)Ph 12 (150 atm. CO) or CP2Mo 2 (C0) 4 (µ-C~) 13 (R = C 6H 5 , 3 atm CO, 50° C) also yields the corresponding ketene. The preparation of tantalum 14 and osmium 15 ketene complexes by carbonylation of a metal carbene have been briefly reported. The most thoroughly examined system showing this type of reactivity to date has been reported by Herrmann and Plank in which the high pressure (650 atm) carbonylation of CpMn(C0) 2 (CPh 2 ) gives CpMn(C0) {0CCP~). 16a Further studies of the less stable manganese 2 Cp f C .....1Mn~ 0 C., '-'=CPh2 0 650 atm ) CO (4) 60 anthronyl carbene complex, in the presence of CpMn(C0) 3 , have suggested that the ketene product is formed by the intermolecular transfer of the carbene to one of the manganese carbonyls of CpMn(C0) 3 • lSb Finally Beauchamp and 5tevens have proposed that CpFe(CO)(CH 2 )+, observed by ion cyclotron resonance spectroscopy, is best formulated as the iron ketene adduct, CpFe(OCCH )+. 17 How2 ever, none of these examples provides clear precedence for the intramolecular carbene-carbonyl coupling step proposed in Scheme I. In this chapter we report the preparation of some stable zirconium oxycarbene complexes by the reaction of cp;ZrH 2 with a bis( cyclopentadienyl) zirconium monocarbonyl complex, a less sterically hindered zirconium carbonyl than C~Zr(C0) 2 • We have also investigated the reactivity of a oxycarbene-carbonyl complex of zirconocene, which undergoes facile carbene-carbonyl coupling to afford a metal-coordinated ketene intermediate, in particular with regard· to the molecularity of the carbon-carbon bond forming step. 61 The treatment of C1>2Zr(L)(CO) (! L =CO, ~ L = PMe3 ) with Cp:ZrH2 (3) in toluene gives an immediate reaction at -78• C to afford the corresponding zirconoxy carbenes, C1>2(L)Zr=CHO-Zr(H)Cp: (f L =PM~, ~ L = CO). In the case of L = PMe3 , 1_ is quite stable in (5) - 1 L =CO 1 L = PMe3 -3 - =CO 5 L solution and can be isolated as red crystals in 84% yield, based on 1 13 C NMR spectra of 4 (Table I) are similar to those of previously reported zirconoxy carbenes, Cp M=CHO-Zr(H)C~ (M =Cr, Mo, W) 3 and starting 3, from a toluene/pet ether solution. The H and 2 Cp(R)Nb=CHO- Zr(H)Cp2* (R = H, CH 3 , CH 2 CJi 5 , CH 2 CJI~OCH 3 ). 2 The carbene carbon and proton resonances appear at low field, 1 287. 5 o and 11. 2 o, with a JCH = 115 Hz. Two resonances are observed in the 1H NMR spectrum for the C5H5 rings, presumably due to the absence of rotation around the zirconium-carbon bond. The TT-interaction of the carbon p orbital and the zirconium la1 orbital in in the equatorial wedge of the Cp2 Zr metallocene fragment locks the carbene ligand with the proton directed toward one ring and the zirconoxy substituent toward the other. The lack of rotation of the carbene also makes the Cp* rings diastereotopic, as indicated by the inequivalent resonance signals in the 1H and 13 C (methyl carbons only) NMR spectra. The zirconium hydride resonance at 5. 7 tj is characteristic of compounds that have a zirconium-oxygen bond in the equatorial plane. 62 -- In contrast to 4, 5 is unstable in aromatic solvents at room temperature. However, Cp2 (CO)Zr=CHO-Zr(H)Cp; can be isolated as a tan powder in 53% yield by performing the reaction in pet ether, whereupon the slightly soluble carbene complex precipitates from solution as it is formed. The 1 H and 13 C NMR spectra of .Q. (Table I) - are similar to those of 4. The zirconium carbonyl exhibits a strong band at 1925 cm- 1 in the IR spectrum and is assigned as the vco· Treatment of~ with ca. 3 equivalents of PMe3 in a sealed NMR tube - results in conversion to 4 over 2 hours at 25 ° C. . - In toluene or benzene solution 5 converts to an extremely in- - soluble yellow crystalline compound (6) within 2 hours at room ternperature. The IR spectrum of this product shows no bands corre- - sponding to a metal carbonyl stretch, and the elemental analysis of 6 indicates that it has the same stoichiometry as 5, (Cp2 Zr)(C 2 H20 2 )(Cp2* Zr). The isolation and purification of Cp2 (CO)Zr=CHO-Zr(H)Cp: is hindered by the ability of a second molecule of cp:ZrH2 to add to ~to afford a new compound, Cp2 Zr(C 2 H2 0 2 )(H) 2 (ZrCp:)2 , (~). This com- - plex is observed as a contaminant in samples of 5 that are prepared under conditions that allow an excess of cp:zrH2 (relative to Cp2 Zr(C0) 2 ) in the reaction mixture. ~can be prepared and purified in 50% yield by treatment of Cp2 Zr(C0) 2 with 2 equivalents of Cp:ZrH 2 • The 1H and 13 C NMR spectra (Table I) of "'"'-"" 5a show resonances for two inequivalent Cp rings, four inequivalent Cp * rings, two different zirconium hydrides and a new ligand, coming from the carbonyls, containing a .:=::CH-CH~ fragment. The chemical shifts of the 63 resonances of CPJZr(CJl202 )(H) 2 (ZrC~) 2 are consistent with the structure shown, but further characterization has not been pursued. -5a Treatment of ~ with 2 equivalents of CH3 I in an NMR tube gives CH4 and a new complex with a 1H NMR spectrum similar to that of 5a, but without the resonance assigned to the zirconium hydrides. - - -- With an excess of CO, in an NMR tube, 4 and 5 give very similar - - product distributions (after a clean conversion to 5 in the case of 4) consisting of CP2Zr(C0) 2 and C~Zr(C0) 2 (identified by m and NMR spectroscopy) as well as an unidentified cp:zr product 1 (Cp:zr(C0) 2 /new Cp:zr about 3: 1) with H NMR resonances at 1. 87 o {30H) and 6. 35 o(2H), consistent with the formulation of C~ZrOCH=CHO. Attempts to isolate this new complex on a preparative scale were un- - successful. Analysis of the gas remaining after the reaction of 4 with CO shows approximately equal equivalents of H2 and cp;zr(C0) 2 are produced (0. 41 equivalents H2 /equivalent 1. vs. 35% of final C~Zr as Cp:zr(C0) 2 by 1 H NMR integration of the remaining tar). Neither 1_ nor ~give clean products in the presence of H2 • Treatment of §. with 1 equivalent of acetone in a sealed N:MR tube cleanly produces Cp2 Zr(C0) 2 64 and cp:zr(H)(OCH(CH 3 ) 2 ) within 5 minutes at RT. These results suggest that the addition of the zirconium hydride to the carbonyl might be reversible, and that the observed products could arise from trapping of liberated ci;zrH2 by CO or acetone. However; an Nl\ffi. sample of~ and 3 equivalents of CJl2Zr(1 C0) 2 shows no 3 13 C incorpor- - ation into the carbene carbon prior to its conversion to 6. Treatment of 1. with an excess of CH 3 I liberates one equivalent of CH 4 and yields green, crystalline C1>2(PMe3 )Zr=CHO-Zr(I)Cp: (1). The 1H and 13 - - C Nl.VIR spectra of 7 (Table l) are vecy similar to those of 1_. In the presence of HCl 1 rapidly gives CP2ZrC~ and Cp:zr(OCH 3 )1.18 Cp2yr=CHO-rrcp: + HC1(2eq) - Cp2ZrCI:i + cp:zr(OCH3)I + PMe3 . PMe3 7 I (8) cooling of a saturated benzene solution. The unit cell parameters and Crystals of 7 suitable for X-ray diffraction were grown by slow data collection and refinement information are given in Table II. Atomic positions, Gaussian amplitudes, bond lengths, and bond angles are given in Tables III-V. shown in Figure 1. Both zirconiums have the pseudo-tetrahedral ORTEPs of 7, with important bond distances and angles are · 65 Figure 1. ORTEP drawings of Cp2 (PMe3 )Zr=CHO-Zr(I)Cp: including important bond distances (A) and angles. 66 coordination geometries common for bent metallocene complexes. The Cp and Cp* ligands are coordinated in the conventional 77 5 manner to the metals; Zr-C and C-C distances for any particular ring are identical within experimental error. The ring centroid-metal-ring centroid angles of 135. 4" and 134. 0° for the Cp2 Zr and cp: Zr fragments are typical for zirconium -bent metallocenes. 19 The Zr(2)C( carbene) distance of 2.117(7) A is the shortest reported zirconiumcarbon bond, being ca. 0.15 .l shorter than that observed for carbon a-bonded to a zirconium center (these values range from 2. 25 Afor (Indenyl) ZrMe 20 to 2. 33A for Cp Zr(Ph)CH(SiMe ) ). 21 The con2 2 2 3 2 figuration of the carbene ligand is such that the proton and the zirconoxy substituents each eclipse a Cp ring in an arrangement that is required by the Zr-C 7T-bond between the carbon p orbital and the la 1 orbital in the zirconium equatorial plane. The relatively short C-0 (1. 377(9) A.) 22 and Zr(l)-0 (1. 940(5) A.) 23 , 24 bond lengths suggest that all resonance structures shown in Figure 2 contribute to the bonding in this compound. - +.........-H M-C "o-R I II - /H M-C~O-R /H M=C, + III Figure 2. Oxycarbene Resonance Structures. IV 0 R + - 67 Treatment of Cp2 (CO)Zr=CHO-Zr(H)Cp: with CH3 I or, under carefully controlled conditions to avoid further reaction, C1>2(PMe 3 )Zr=CHO-Zr(I)C~ with CO, yields a new intensely purple 1 . compound, Cp:zrOCH=C(Zr(I)C1>2)0 (~). The .. H N:M.R spectrum (Table I) shows signals for the C5 H5 and C5Me 5 rings and a resonance, integrating to one proton, at 6. 8 o. The 13 C NMR spectrum of a sample prepared from C1>2(PMe3 )Zr= CHO-Zr{I)C~ {60% 13 enriched) and 13 CO (99% 13 downfield at 234. 97 6 (99% 13 C C enriched) shows two large resonances 13 13 C enriched) and 155. 01 o (60% C enriched) 1 with a Jcc = 45 Hz, and indicates that the carbene and carbonyl carbons are coupled in the final product. The gated decoupled spec·trum shows carbon-hydrogen coupling constants of 1 JCH = 180 Hz and 2 JCH = 24 Hz, values that are consistent with the formation of a new 13 CO gives incorporation of the labeled carbon only into the resonance at 235 o with the carbon-carbon bond. Treatment of unlabeled 7 with 2 small JcH· The IR spectrum of a nujol mull of~ shows no evidence of any metal carbonyls. The extensive rearrangement that is necessary to transform - either of the starting carbene complexes to 8 made the assignment of its structure impossible simply from the spectral data. Therefore suitable crystals for a single crystal X-ray diffraction structure determination were grown by slow cooling of a saturated benzene solution. The unit cell parameters as well as data collection and refinement information are given in Table VII. Atomic positions and Gaussian amplitudes, bond lengths and bond angles are listed in Tables VIII-X. - ORTEP drawings of 8 (Figure 3) confirm the structure of a 68 Cp(I) Cp(2) Figure 3. ORTEP drawings of Cp:zrOCH=C(Zr(I)Cp:)o including important bond distances (A) and angles. 69 z'irconium substituted enediolate zirconocycle. Both zirconium atoms have pseudo-tetrahedral coordination geometries and the metal-to-ring bonding for the Cp and Cp * ligands is similar to that seen in the struc- experimental error (Table XI lists deviations from the least-squares ture of 7. The five-membered metallocycle ring is planar within plane). The Zr(l)-0 distances of 1. 999(7) A and 2. 073(7) A fall between those observed for zirconium acetylacetonate complexes 22 (2.10 - 2. 25 A; mixture of covalent and dative Zr-0 interactions) and zirconium µ-oxo dimers 23 (1. 95 A; covalent Zr-0 bond with significant 'IT-bonding). The fact that the C-C bond, 1. 402(14) A, is slightly longer than that expected for a C-C double bond and the C-0 bonds (1. 352(12), 1. 333( 12) .A) are shorter than values for normal C-0 single bonds 25 indicates that there is some 7T-delocalization throughout the metallocycle. Inclusion of a high-energy, empty zirconium orbital perpendicular to the bent. metallocene equatorial plane and one lone pair on each oxygen with the C-C 7T-bond gives a 6-electron aromatic 1T framework consistent with the observed stability of molecules with a metallocycle enediolate structure. The orientation of the Cp2 Zr(I) fragment, with the Zr and I atoms in the metallocycle plane, suggests that the metallocycle 7T-system delocalizes onto the Zr(2) center as shown by resonance structure II in Figure 4. The Zr(2)-C bond length, /o--c--Zr ll Zr "o--C-._H I - 0---c::::::=: Zr Zr l ~ o-:=:::: H + / c__ II Figure 4. Enediolate Metallocycle Resonance structures. 70 2. 268(10) A, is slightly shorter than the average observed for zirconium carbon cr bond lengths, l 9 , 20 and is consistent with 7T-interaction between these two atoms. The extended 7T-delocalization increases the C(2)-0(2) bond order while weakening the Zr-0(2) bond, relative to the corresponding bonds involving 0(1), thereby accounting for the different lengths of two Zr-0 and two C-0 bonds within the metallocycle. The molecularity of the carbon-carbon bond forming step that experiment. Treatment of a mixture of Cp Zr(1 C0) and Cp Zr(1 C0) leads to the generation of 8 was determined by an isotopic cross-over 2 3 2 (91% 13 2 2 2 C enriched) with cp;ZrH 2 followed by CH3 I yields~ with only 5 ± 5% isotopic scrambling (Table XII); this value is indicative of an intramolecular carbonyl-carbene-coupling step. These results suggest that the transformation of the carbene compounds, might be initiated by coupling of the two ligands to give a carbonyl complex to 6, which is not seen for the carbene-phosphine metal-bound ketene intermediate which oligomerizes or rearranges to give the isolated product. The reactivity of §.. with Lewis bases is of interest as these substrates are useful for stabilizing other Group IV metal ketene complexes by binding to the remaining coordination site on the metal, 26 thereby preventing oligomerization or further rearrangement. Thus addition of ca. 4 equivalents of pyridine to an NMR sample of§.. in C 6 D6 affords a pyridine-trapped zirconium ketene complex, ~' rather than 6, after 2 hrs at room temperature. 9 can be isolated in - - 71 H I /T * ~c~ Cp2 Zr=CHO-ZrCp2 + pyr ~ Cp2 Zr\-O I CO I 5 . H pyr 9 o, ZrCp: H (9) / 82% yield by either dissolving 1 in pyridine or treating Cp2 Zr(C0) 2 with Cp; ZrH 2 in pyridine and precipitating the red product with pet ether. The H NMR spectrum of~ (Table 1) in C 5 D5 N has single 1 resonances for the Cp* and Cp rings at 2.180 and 5.91 o. No resonance can be assigned to the zirconium hydride in the 90 MHz spectrum; however, the 500 MHz spectrum has a small shoulder on the Cp peak at 5. 92 0 in the region where the resonance for the hydride is expected to be. A peak integrating to one proton appears at 6. 18 0 and is assigned as the resonance of the ketene hydrogen. This assignment is confirmed by the spectrum of 9 with the ketene carbons enriched in -"' 13 C, prepared by treating Cp2 Zr( 13 C0) 2 (70% 13 C enriched) with cp;zrH 2 1 2 in C 5 D5 N, which shows this resonance split by JCH and JCH of 183 and 22 Hz. The 13C NMR spectrum (Table I) of the 13 C enriched sample of~ shows the ketene carbon resonances at 165. 7 o ( JCH = 22 Hz) and 2 1 123. 4 o (1 JCN = 183 Hz) with Jee = 78 Hz confirming that the product has a new carbon-carbon bond. The ketene complex is stable for over a month at room temperature in pyridine solution. In benzene or toluene, however, 9 gives 6 (identified by IR), releasing pyridine, -"' -"' until an approximately five-fold excess of free pyridine to 9 is reached; -"' complete conversion to §_ can be achieved by removing the pyridine in vacuo. Treatment of ~ in C5 D5 N with one equivalent of CH 3 I in a sealed 72 1 NMR tube affords a new complex, ,,.....,,... 10, with H and 13 C NMR spectra (Table I) similar to those of 9. A small peak due to CH 4 is also seen '"" in the spectrum of the reaction solution. On a preparative scale this reaction yields 0. 88 equivalents of CH4 , collected and measured with a Toepler pump; however, !Q can be isolated only as an impure red tar. These results are consistent with the formulation of 10 as "-"- Cp2 (pyr)Zr(O=C=CHO-Zr(I)Cp2*). 10 (10) When the reaction of ~ and CH 3 I is carried out in benzene or the 1 isolated red tar is dissolved in C 6 D6 , the H spectrum obtained is 1 identical to that of §_. Conversely, the H NMR spectrum of a C 5 D5 N solution of 8 is identical to that of 10. These results indicate that an '"" "-"- equilibrium exists between 8 and 10, depending on pyridine concen'"" "-"- tration. (11) 10 8 73 Other Lewis bases, such as phosphoranes, amines, or acetonitrile, are not useful for trapping of the zirconium ketene inter~ mediate. Treatment of~ with CH 2 PMe3 gives a complex mixture of unidentifiable products. NMe3 is presumably too large to bind to the sterically hindered zirconium center and therefore does not affect the conversion of ~ to ~· In a manner similar to PMe3 , acetonitrile complex; however, this unstable intermediate has defied isolation. apparently displaces the remaining carbonyl of 5 to give a new carbene - Hydrogenation of 9 under a variety of conditions, in an attempt to obtain precedence for the final step of Scheme I, leads to a mixture of unidentifable products. 74 The general reaction, shown in eq. 1, of the reduction of a transition metal carbonyl by bis(pentamethylcyclopentadienyl)zirconium dihydride has been extended to afford some of the first isolable examples of Group IV transition metal-carbon multiple bonding. Zirconoxy carbene complexes of bis(cyclopentadienyl)zirconium have been prepared by the treatment of the corresponding zirconium carbonyls with cp:ZrH2 • The ready formation of 1. and.§.. lends support to the proposed initial step of the mechanism for the formation of cis-(Cp:ZrH) 2 (µ-0CH=CHO-) from Cp:zr(C0) 2 and 1 Cp:ZrH2 under H2 (Scheme I). ld Comparison of the H NMR spectra of this reaction in the absence of H supports its formulation as a of 4 and 5 with that of the transient species observed during the course 2 zirconium carbene intermediate. The large difference in the rate of attack of cp;ZrH2 on the Cp2 Zr and cp:zr carbonyls is probably due to the increased steric hindrance of the bulky Cp* ligands. In addition, it may also be argued that the Cp: Zr car bony ls are less susceptible to nucleophilic attack because of the greater electron-releasing character of the pentamethylcyclopentadienyl ligands relative to that of the cyclopentadienyl rings. However, replacement of one of the carbonyls of !. with PMe 3 , which increases the electron density on the remaining carbonyl, has no noticeable effect on the rate of carbene formation. A comparison of the carbonyl stretching frequencies of ~ (v CO = -1 1852 cm ) 27 * -1 and Cp2 Zr(C0) 2 (vCO(sym) = 1945 cm , vCO(asym) = - 1852 cm -i)l 8c indicates that the carbonyl of 2 is more electron rich 75 than those of cp:zr(C0) 2 ; that cp:ZrH 2 adds much more rapidly to~ than to cp:zr(C0) 2 discredits arguments that the difference in rates is due to electronic effects. The bonding of a carbene ligand to a transition metal can be represented by the resonance structures I-III in Figure 2. structure I describes the covalent bonding limit with the 1T electrons equally shared between the two atoms. If there is no 'IT-back-bonding from the metal to the carbon the carbene is a a -donating ligand only, illustrated by structure II. This structure may be stabilized, in the case of heteroatom substituted carbenes, by delocalization of a lone pair of the heteroatom onto the carbene carbon as represented by structure III. Fischer-type carbenes, in which the heteroatom substituent is usually an alkoxide or amide, are best described by III; 28 the electron donation by the 0 or N atom makes the carbene a good a -donor but a poor 1T acceptor. The electron deficiency of the carbene ligand is demonstrated by its reactivity as an electrophilic center. In contrast, early metal alkylidene complexes, such as Cp2 Ta(CH3 )(CH 2 ) are better represented by I. 29 The presence of a strong 'TT-interaction is shown by the high barrier to rotation around the metal-alkylidene bond. Calculations on the model molecule, CpMn(C0) (CH ), 30 have deter2 2 mined that the empty methylene 'TT-orbital and occupied metal orbital with which it interacts are similar in energy, consistent with a significant 'TT-interaction. The nucleophilic character of the alkylidene carbon also attests to it being a good 'TT-acceptor ligand. 31 The results of our research suggest that the electronic nature of the zirconoxy carbene ligand lies between these two extremes. The 76 ability of the Cp:(H)Zr(IV) center, as a Lewis acid, to remove electron density from the oxygen atom by interacting with one of the lone pairs in a 1T manner, illustrated by structure IV of Figure 2 where R is the electropositive cp:zr moiety, reduces the oxygen donation in the reverse direction. This makes the zirconoxy carbene ligand a better 'TT-acceptor than other Fischer-type, oxygen stabilized carbenes. The increased strength of the 7T-bonding interaction is apparent from the inequivalency of the two Cp resonances in the 1H NMR spectra of -- - 4, 5, and 7 indicative of restricted rotation around the zirconiumcarbene bond. The carbonyl stretching frequencies of some zirconocene carbonyl complexes provide additional insights on the electronic nature of the carbene ligand. The CO stretching frequency 1 of 5 (1925 cm- ) is very similar to the mean CO stretching frequency - of _1 (193 O cm -l from vCO(sym) = 1975 cm - l and vCO(asym) = 1886 cm -1)32 suggesting that replacement of the carbonyl by the zirconoxy carbene does not significantly change the electron density in the bent metallocene equatorial plane. The vco of§. is much higher than that of~ (vco = 1852 cm- 1 ). 27 These results suggest that the zirconoxy carbene is a good 7T-accepting ligand, comparable to CO in its 1T back-bonding with the zirconocene fragment. The carbon-hydrogen stretching frequency of the zirconoxy car- - bene C-H bond appears at relatively low energy in the IR spectra of 4, §_, and 1 (2755, 2755, 2755 cm-1, respectively). It has been argued that distortion of the carbene ligand by lessening the metal-carbonhydrogen angle parallels the lowering of vCH' 33 perhaps because both are measures of the carbon p character of the C-H bond, which should 77 -- - be increased in 4, 5 and 7 due to demand of the electropositive zirconium for more carbon s character in the metal carbene a bond. The oxycarbene-carbonyl complexes of zirconocene that we have prepared undergo a facile rearrangement to a zirconium ketene inter- - mediate by coupling the two equatorial ligands. In the case of 4 the -- ketene adduct, 11, can be trapped by pyridine to afford the isolable In the absence of a trapping ligand ll apparently isomerizes or oligomerzirconium ketene pyridine complex, 9, as outlined in Scheme II. - izes to give 6. The replacement of the remaining zirconium hydride of Cp2 (CO)Zr=CHO-Zr(H)Cp: with an iodide, either by treatment of~ with Mel or 1 with CO, results in a carbene carbonyl iodide complex, ll, which can couple to a new ketene adduct, ll· However, neither of -- these intermediates has been detected. Instead, 13 rearranges to cp:zrO-CH==C(Zr(I)Cp2)0 by exchange of the iodide and carbonyl oxygen atoms between the zirc.oniums (Scheme III). Presumably, the formation of the five-membered metallocycle is the driving force of this process. Several other Group IV transition metal complexes containing a cyclic enediolate substructure are known 24 ' 34 and have properties similar - -- to 8. The formation of a ketene pyridine complex, 10, when reactions that give ~in benzene are performed in pyridine, as well as the observed interchange of ~ and !Q, depending on pyridine concentration, gives strong support for the presence of a ketene intermediate on the - 13 -8 and 9 indicates that this compound is best formulated as a zirconium pathway to 8. Comparison of the - - C NMR spectrum of 10 to those of - ketene complex with a structure similar to that of 9. Scheme II H I c~c....._o Cp 2 Zr=CHO-Z{Cp~ ~O ~ I cp 2zr(b H)zrcp~ ~ CpzZr(CzHzOzlZrCp~ H - - 6 5 pyridine ~ CX) H I C:;::::::::-C--.........0 CpzZr~ ~ ~ZrCp~ pyr Mel benzene 9 '/ J>---c------" II c *Zr. Pz \ -E-zrcp 0 1/ 8 2 Scheme III / co CpzZr'c- OZrcpi I H .. ~o I I • /c ? cp 2zr, I H~~c'"~OZrCpz* · • I Cp 2Zr-p+.ZrCp~ 'c I 'c,..o I H/ l 12 ,,,.a:, l 13 .~ ~ /I Cp2Zr, Q c--- \ II ZrCp~ C-......ol H/ 8 1 -:] co 80 The coupling of the carbene and carbonyl ligands described above can be rationalized by consideration of the metal-ligand bonding in the equatorial plane of the Cp Zr fragment. 35 The a -bonding, 2 derived from the ligand lone pairs and the empty metal b2 and 2a1 orbitals, and 'TT-bonding, involving the zirconium la1 , carbene 1T and carbonyl 7T* orbitals, are illustrated in Figure 5. Complete transfer H J. .o zrO Cj c~ ~o 7T Figure 5. Bonding in the Zirconium Equatorial Plane in~of the 1T electron pair from the metal to the ligand orbitals, to give a new C-C a bond, with the simultaneous transformation of the ligand a-donated electrons to covalent metal-ligand bonds gives the zirconium ketene complex in the Zr(IV} resonance structure (Figure 6a). This H 1,,,.,.0 c Cp2 Zr-ll c~ a b Figure 6. Zirconium-Ketene Resonance Structures. 81 intermediate can also be drawn as a zirconium(II) olefin adduct (Figure 6b). The proposed migration of the CP2Zr group to the carbonyl is similar to the fluctionality proposed for the iron allene bonding in (C0) Fe(Me C=C=CMe ) 36 and is probably driven by the 4 2 2 zirconium-oxygen interaction that is attained. This interpretation of the carbene-carbonyl coupling mechanism suggests that the process should be favored by metal centers that can - be easily oxidized, particularly if, as in the case of 5, the HOMO of the complex is a metal orbital 'IT back-bonding to both the carbene and carbonyl ligands. The electrophilicity of the carbene ligand should also affect the coupling process. Therefore, heteroatom stabilized carbenes, in which the overlap of the carbene rr orbital with the metal orbitals is diminished by the heteroatom donation, should be less susceptible to coupling than carbenes that have no such substituents. A final point of consideration is that the carbonyl-carbene coupling may be assisted by Lewis bases, such as pyridine or iodide, which promote the electron transfer from the metal to the ligands by interacting to the zirconium la1 orbital of the carbene carbonyl complex. However, the fact that roughly similar rates are observed for the conversion of Cp2 (CO)Zr=CHO-Zr(H)Cp: to~' in the presence of 4 equiva- - lents of pyridine, or 6, in the absence of pyridine, as well as the formation of!!_ from CP2(CO)Zr=CHO-Zr(I)Cp: suggests that any rate enhancement of the coupling step due to the presence of a Lewis base is minimal. Attempts to prepare (Cp2 ZrH)(µ-OCH=CHO-)(Cp:ZrH) by hydrogenation of 1,,,....,...O, similar to the last step proposed in Scheme I 82 have been unsuccessful. The presence of pyridine may slow the addition of H2 to the Cp2 Zr center allowing other reaction pathways to become competitive. However, a very similar Lewis base stabilized zirconium ketene complex, Cp:(L)Zr(O=C=CHCMe3 ) (L = pyr, CO, CH2 PMe 3 ) has been shown to hydrogenate cleanly to Cp:zr(H)(OCH=CH(CH2 CMe 3 )), with a cis-arrangement of the bulky substituents on the C=C bond. 26b 1 atm H2 ) 25° (12) The results described above provide clear precedence for the carbon-carbon bond making step proposed in Scheme I for the formation of cis-(cp;zrH) 2 (µ-0CH=CHO-). The carbene and carbonyl ligands of Cp;(CO)Zr=CHO-Zr(H)Cp; should be more susceptible to coupling to those of §. since the more electron-releasing nature of the Cp* rings, relative to Cp rings, should facilitate the transfer of the 1T electrons to the ligands by destabilizing the zirconium la 1 orbital. Table I. NMRa and mb Data. NMR Compound IR CJ>..a(PMes)Zr=CHO-Zr(H)C~ (4) v(C-H) v(C-D) 2755 2045 assignment 1u Zr=CHO-Zr 11. 29 5. 35, 5. 44 2. 00, 2. 04 ~~ C 5 (CH,) 5 19 3 3 Jpu=3 Jpff=2, 2 ~(C.Hs)5 P(CH,)3 Zr!!_ Cp_.(CO)Zr=CHO-Zr(H)CP! (5)c v(C-H) 2755 v(C-D) 2042 v(CO) 1925 v(Zr-H) 1515 Zr=CHO-Zr C5H5 C 5 (CH,) 5 o. 93 aJpu=6 11. 58 295. 02 98. 64, loo. 28 11.61 116.23 5.44,5.43 1.95,1.93 ga!!·CbH CaH-~t>!! CJ!e Cs(C!!s)i; Zr!! CJ>..a(PMe3 )Zr::CHO-Zr{I)C~ (7) v(C-H) v(C-D) 2725 2020 Zr=CHO-Zr Cs~ C5(C!!:J)s P(C!!:J)3 l Jcu=l05 Jca=l 72, 176 1 Jca=l27 1 5.47 262.11 Zr(£0) CJ>..aZr(CJf 403 )(ZrC~)a (5a)c l a 287. 54 Jca=115, Jcp=14 100.20,101.58 11.79, 12.22 116. 67 1 20. 33 Jcp=lB 5.70 ~(CHs)5 Zr!! C{1H} 3 7. 62 Juu=lO 3 5. 45 JHH=10 6.26,6.21 2.00,2.02 2.03,2.08 5.71,6.34 10. 69 5.48,5.55 2.07,2.13 o. 93 3 Jpff=4 3 Jpu=2,2 2 Jpa=6 155. 82 144. a2 286.32 1 1 1 Jcu=l69 Jca=111 Jca=117 1 2 Jcc=69 Jcp=14 CX> ~ Table I (continued) Compound c~ZrOCii::C(zr(I)C~)o (8) IR assignment iH isc _Z~OCH=C(Zr)O 6.77 155. 01 6.07 1.87 234. 97 JCH=24 111. 03 11.18 not assigned 6.20 5.91 2.20 165. 65 123.40 107.50 11. 67 116. 90 ,- I ~5(CHs)s C~(pyr)Zr(O=C=CHO-Zr(H)Cp: (9)d O~=CHO-Zr O::C=CHO-Zr ~5!!5 Cs(CHs)15 ~s(CHs)15 Zr!! Cll,a(pyr)Zr(O=C=CHO-Zr(I)C~) (10)d 0=£=CHO-Zr O::C=CHO-Zr !;s!!s Cs(Q!!s)5 £s(CHsls l Jca=l8o, Jcc=45 2 ZrOCH=£(Zr)O !;J!5 C5(Q!!s)15 l 2 l Jcu=22, Jcc=77 1 Jcu=183 1 Jca=l70 1 Jcu=126 5.92 6.28 5.96 1.77 170. 81 124.44 108.19 11.05 114. 58 1 Jcc=73 a) NMR spectra in benzene-~ at 34• Cat 90 MHz (1H) or 22.5 MHz (13C) unless otherwise noted. Chemical shifts in~ measured 13 from internal TMS, coupling constants in Hz. All C NMR samples were enriched with 13 C at the non-ring and nonphosphine carbons. b) IR spectra recorded as nujol mulls. Values given in cm - i . Detailed spectra are listed in the experimental section. c) 1H NMR spectrum recorded at 500 MHz. d) Spectra recorded in pyridine-!!s. CX> .i:. 85 Table II. Crystal and Intensity Collection Data for CP2(PMe3 )Zr=CHO-Zr(I)Cp: • C 6H6 Fonnula Fonnula weight Space group a v C34H5oOPZrzI.C6H6 893. 03 . g/mol C2/c * 27.318(4) R 19.895(3) R 19.932(5) R 132.188(10) 0 8027(3) .R3 z 8 b c a Peale Crystal size A µ Scan range 26 limits, scan rate, bkgrd time/scan time, number of reflns Total number of averaged data Refinement on Weights w defined as Final number of parameters Final agreement RF (F 2 > O) · 2 0 Ri= (F > 30F2) l\vp(F~ > O) s 1.48 g/an3 0.60 x 0.21 x 1.00 J1D'n 0.71069 R (MoKa, graphite monochromator) 1..338 J1D'n -l 1.0° in 26 below Ka1 1.0° in 28 above Ka2 3-35° 4.88 deg/min 1.0 3-35 8.37 1.0 3.91 35-46 1.0 2.02 0.5 45-54 3-30 9.77 1.0 8169 (7961t) reflections 2599 2128 1960 5302 3501 (+h,+k,!1) (+h,+k,!l) (+h,+k,+l) (+h,+k,~l) (+h,+k,+l) F 2 0 ra:2 + 0.02 x (scan counts) 2 ]- 2 138(coords) + 241 (U's) + l(scale) = 160 0.082 (4604 reflections in sums) 0.050 r 0.104 1.74 *Data collected in 12/a: ~=19.932(5), b=19.895(3), c=20.303(2) R, 6=94.482(9) 0 ; all subsequent calculations carried out in C2/c. t208 reflections deleted before final cycle of refinement; s;e text. TR_= El IF 0 I-IF c I j/EIF0 I, sums only include the 7179 reflections with F02 > O; -"F 2 -F 2) 2 /EwF 4 }~, sums include all 7961 reflections; RF= {rw(F w . 0 e 0 S = {Ew(F 0 2 -F c 2 ) 2 /(n-p)}~. 86 Table III. Part A. Atomic Coordinates (x 104 ) for C1>2(PMe 3 ) 2 Zr=CHO-Zr(I)C~ • C6 H6 % 3004.8 2 I Zr(l) 3152.4 3 Zr(2) 42.46.9 3 p 3544.8 8 C(l) 4389 4 gm 0 c 4) c 11 c 12 c 13 c 14 c 15 c 21 c 22 c 23 c 24 c 25 C(31 C(32 C(33~ C(34 C(35 C(41) C(42) cC!43! 44 c 4c 5~ C(52) C(53) c 55 C!54! c 61 c 62 C(63 c 64 c 65 c 71 c 72 c 73 c 74 c 75 C(16 H(4) 3512 4 3104 4 3968 2 3895 3 3525 4 2963 4 3070 4 3730 4 4012 3 2196 3 2511 3 2432 3 2073 3 1926 3 5167 4 5402 3 5007 3 4525 3 4615 4 5541!5 6053 4 5118 4 4013 4 4291(4'! 4706!3 4007 3 3719 3 4225 3 4843 3 5201 4 3660 4 2996 4 4134 5 5506 4 1454 5 987 6 855 5 1199 5 1708 6 1838 5 4251(27 !I 2451.9 3 997.4 3 2469.3 3 -231.5 9 -464 4 -394 4 -957 4 1870 2 1516 3 421 4 785 4 1464 4 1538 4 902 4 611 4 1117 4 1722 4 1603 4 905 4 2341(3 2039(4 1477(3 1442 3 1965 3 2852 4 2179 5 978 4 878 4 2028 5) 3299 3~ 3323 3 3598(3, 375613) 3599 3· 3090 4 3143 4 3806 4 4128 4 3854 4 959 5 479 6 97 6 179 5 643 6 1047 5 1547(26 z 3765.7!3 1334.7 4 4187.4 4 2097.2(12 2681 5 2964 5 1360 5 3217 2 2564 4 597 5 -83 5 93 4 899 5 1221 5 1161 6 1793 5 1399 5 479 5 320 5 5962 4 5579 4 5079 4 5136 4 5673 4 6725 5 5829 5 4637 5 4730 5 6051!5 4~ 3761 4 . 3011 4 3323 424~(5 4518 4 3694 5 2048 5 2696 6 4819 6 5339 5 3819 7 3382 8 2731 7 2470 7) 2939 8) 3610 7) 2638(35) 87 2 - 4 Table m. Part B. Gaussian Amplitudes (A , x 10 ) for 7. I Zr( I) Zr(2) p gm 0 c 4) c 11) c 12 c 13 c 14 c 15 c 21 c 22 c 23 C(24 C(25 C(3I) C(32) C(33 C(34 35 c 41 42 Uu U22 U33 U12 U13 496!3 300 3 368 3 427(9 666(3 454(3 393(3 451(10 776(4) 332\3) 367(3) 476(10) 72(3l 12(3 538~45 673~51 995(63~ -194~47 500(3) 177(2) 254(3) 252(9) 444( 47) 457(46) 476( 49) 150(18) 846 56 925 60 299 21 351 32 956 62 1038 68 677 49 769 53 596 45 395 39 456 39 467 40 404 38 278 33 667(46 484(40 527!38) 594 42) 720 47 1505 91 498}46 916 59 824 58 c c cc 43~ 44 c 45 1122~75 c 51) 393 32) c 52) cc 53l 54 C(55 C(61) C(62 C(63 C(64 C(65 C(71) C(73) C(75) H(4) 459 37) 485~39) 714 46) 560 42) 632 49) 722 51) 660 53l 1487 89 889 61 113(3)* 117(3)* 121( 4)* 48(17)* 662 50 568 46 493 26) 496 38 693 54 765 58 875 57 740 53 1072!66 634 50 1058 65 632 48 893~58 987 63 626 48 695 48 559( 42) 498(40!( 576( 44 871(63 1061 66 874 56) 517 43) 1397 82 500 38 475 38 452 39 493 39 439 38 880~58) 49~54! 765 59 724 60 723 55 591(47 788(53 290 21~ 342 32 742 54 555 47) 368 38) 653 48 599 45 1138 69 671 48 875 57 541 45 671 49 341{35l 428(39 376(35l 452(38 486!'40) 476 48) 804 58) 567 45) 928 60) 787 60) 453 36) 402 36) 675 47) 659 45) 520 41) 841(55l 431 41 1512 83 1353 80) 722 53) 2ml) 135 39 -47 42 -16 37 18l 27 14 45 -128 48 -171 45) -170 42 225 46 -51 35 70 42 110 36 182 39 -32 39 -72 36 9 35 79 34!' 10 33 27 37 -347 62 70( 45) 414( 51) -119(41) 313~62(~ 57\28 50{30 l 73(30l -23 35 -99(31 -9(42) 59(42) 346(44) 18(58) -414(47) C(72) C(74) C(76) *Isotropic Gaussian amplitude (A.2 , x 103 ). 225~28 691 53 597 51 290(38 ~~gm! 494(47 429(39 448(43 208(36) 178(35) 27 4(35) 266(34) 284(33) 340(36) 460( 40) 541(59) 269( 44) 487(45) 500(52~ 815~62 323l31 260(32) 400(38) 577( 42) 375(38) 592( 47) 294(41) 681(60) 1222(78) 441( 49) 134( 4)* 113(3)* 114( 4)* 12Y~~ j 3 14 3 28 3 25(8l 135( 46 115(39l -126(46 -43~19~ 6 28 -49 43 -85 '42) -82 40) -83 41) 239 46) -56 48) 68 47) 40 431 25 43 -293 47 -39(32) 135(36) 82 33' 85 32 56 35 -244 46 400 51 134}'45 84 44 269 57 82(30 120(30~· 266(34 -6(35 -8(31) 95( 46) l41r39) 638f 57) -84(56) -161( 44) 88 4 Table III. Part C. Hydrogen. Coordinates (x 10 ) and 2 U's (A ), x lo'3) for 1· H(ll) H(l2) H(I3) H(21) H(22) H(23) H(31) H(32) H(33) H(ll) H(12) H(13) H(l4) H(15) H(2I) H(22) H(23) H(24) H(25) H(411) H(.412) H(413) H(421) H(422) H(423) H(431) H(432) H(433) H( 441) H(442) H(443) H(451) H( 452) x y z 4731 -77 3123 4454 -554 2229 4538 -890 3060 3700 24 3419 3007 -430 2659 3734 -806 3312 2625 -948 1125 3115 -984 889 3323 -1388 1792 3671 -156 708 2616 254 -530 2711 2017 -290 3965 2017 1216 4481 672 1740 2096 177 1037 2712 961 2422 2544 2247 1498 1833 1752 -247 1661 573 -286 5751 3214 6630 5255 3083 6811 5938 2620 7360 5981 2464 5373 6375 2407 6461 6252 1712 5873 .5467 1151 4597 4698 838 4017 5330 531 5030 3739 896 4889 3730 844 4050 42.85 402 5008 4267 2576 6129 4608 1843 6689 u 89 89 89 89 89 89 89 89 89 85 85 85 85 85 85 85 85 85 85 94 94 94 94 94 94 94 94 94 94 94 94 94 94 89 Table III. Part C. (continued} H(453) H(611) H(612) H(613) H(621) H(622) H(623) H(631) H{632) H(633) H(641) H(642) H(643) H(651) H(652) H(653) H(71) H(72) H(13) H(74) EI(75) H(76) x y z u 3861 5603 4992 5247 3258 3992 3585 2958 2922 2700 3881 4513 3752 5490 5856 5645 1520 703 458 1074 2000 2252 1843 3309 3154 2543 3433 3270 2659 4298 3793 3500 4595 4177 3863 4325 3740 3569 1307 393 -293 -136 716 1422 5651 4125 3038 3789 1674 2004 2012 2547 3193 2230 4442 5379 4723 5434 5278 5887 4330 3604 2405 1897 2732 3980 94 99 99 99 99 99 99 99 99 99 99 99 99 99 99 99 139 139 139 139 139 139 90 - Table IV. Bond Distances (A) in 7. Zr(2)-P P-C(l) P-C(2) P-C(3) Zr(2)-C(4) C(4)-H(4) C(4)-0 Zr(l)-0 Zr(l)-I Zr(2)-C(ll) Zr (2) -C (12) Zr (2)-C (13) Zr (2) -C (14) Zr (2) -C (15) C(ll)-C(12) c (12) -c (13) C(13)-C(14) C(14)-C(15) C(lS)-C(ll) Zr(2)-Cpla Zr(2)-C(21) Zr(2)-C(22) Zr (2) -G(23) Zr(2)-C(24) Zr (2) -C (2~) Zr (2) -Cp2 C(21)-C(22) C(22)-C(23) C(23)-C(24) C(24)-C(25) C(25)-C(21) Zr(l)-C(31) Zr (1) -C (32) Zr (1) -C (33) Zr(l)-C(34) 2.693(2) 1.81(1) 1.81(1) 1.82(1) 2.117(7) 0.93(7) 1. 377 (9) 1. 940 (5) 2.900(1) 2.554(10) 2.543(10) 2.507(9) 2.498(9) 2.514(9) 1. 385 (13) 1.376(13) 1.401(13) 1. 395 (13) 1.418(13) 2.23 2.515(9) 2.473(9) 2.512(9) 2.509(9) 2.500(9) 2.20 1. 373 (13) 1.373(13) 1.402(12) 1.421(12) 1.427(13) 2.636(8) 2.574(8) 2.532(8) . . 2. 530 (8) Zr(l)-C(35) C(31)-C(32) c (32) -c (33) C(33)-C(34) C(34)-C(35) C(35)-C(31) C(31)-C(41) c (32) -c (42) c (33) -c (43) C(34)-C(44) C(35)-C(45l Zr (1) -Cp*l Zr(l)-C(Sl) Zr(l)-C(52) Zr (1) -C (53) Zr(l)-C(54) Zr(l)-C(S5) C(Sl)-C(52) c (52) -c (53) C(53)-C(S4) C(54)-C(55) C(55)-C(51) C(Sl)-C(61) c (52) -c (62) c (53) -c (63) C(54)-C(64) C(55)-C(65l Zr(l)-Cp*2 C(71)-C(72) C(72)-C(73) C(73)-C(74) C(74)-C(75) C(75)-C(76) C(76)-C(71) 2.605(8) 1.419(11) 1.402(11) 1. 395 (11) 1. 391 (11) 1.413(11) 1.518(13) 1.517(13) 1. 48 9 (12) 1. 533 (12) 1.506(14) 2.283 2.540(7) 2.597(7) 2.599(8) 2.564(8) 2.588(8) 1.432(10) 1.399(11) 1.405(11) 1.418(11) 1. 419 (1 O) 1. 503 (11) 1.506(11) 1. 523 (13) 1.519(14) 1. 495 (12) 2.280 1.344(20) 1.328(20) 1.355(18) 1.382(19) 1.386(19) 1.378(18) aCpl = C(ll)-C(15) ring centroid, Cp2 = C(21)-C(25) ring centroid, Cp*l = C(31)-C(35) ring centroid, Cp*2 = C(Sl)-C(55) ring centroid. 91 - Table V. Bond Angles (deg) in 7. I-Zr (1)-0 Zr (1)-0-C (4) 0-C(4)-H(4) 0-C(4)-Zr(2) H(4)-C(4)-Zr(2) C(4)-Zr(2)-P Cp*1-Zr(1)-Cp*2a Cpl-Zr(2)-Cp2a Zr(2)-P-C(Ml) Zr (2)-P-C (M2) Zr (2)-P-C (M3) C(ll)-C(12)-C(13) C(12)-C(l3)-C(14) C(l3)-C(14)-C(15) C(14)-C(l5)-C(ll) C(15)-C(ll)-C(12) C(21)-C(22)-C(23) C(22)-C(23)-C(24) C(23)-C(24)-C(25) C(24)-C(25)-C(21) C(25)-C(21)-C(22) C(31)-C(32)-C(33) C(32)-C(33)-C(34) C(33)-C(34)-C(35) C(34)-C(35)-C(31) C(35)-C(31)-C(32) 95. 8 (1) 165.8(4) 110{4) 139.7(5) 109 (4) 95. 0(2) 134.0 135.4 116.5(3) 116. 3 (3) 117. 9(3) 110.9(8) 106.5(8) 108.7(8) 107. 7 (8) 106.1(8) 110.9(8) 107. 7 (8) 107.6(8) 107.1(8) 106. 7 (8) 108. 0 (7) 107.5(7) 109.6(7) 107.4(7) 107.5(7) C(35)-C(31)-C(41) C(32)-C(31)-C(41) C(31)-C(32)-C(42) C(33)-C(32)-C(42) C(32)-C(33)-C(43) C(34)-C(33)-C(43) C(33)-C(34)-C(44) C(35)-C(34)-C(44) C(34)-C(35)-C(45) C(31)-C(35)-C(45) C(Sl)-C(S2)-C(S3) C(S2)-C(S3)-C(S4) C(S3)-C(S4)-C(SS) C(54)-C(SS)-C(Sl) C(SS)-C(Sl)-C(52) C(55)-C(Sl)-C(61) C(S2)-C(S1)-C(61) C(Sl)-C(S2)-C(62) C(53)-C(52)-C(62) C(52)-C(53)-C(63) C(54)-C(53)-C(63) C(S3)-C(S4)-C(64) C(55)-C(54)-C(64) C(54)-C(S5)-C(65) C(Sl)-C(SS)-C(65) 125.4(8) 125.4(8) 126. 9(7) 123.6(7) 125.9(7) 126.4(7) 124. 7 (7) 125.5{7) 125. 2 (7) 126.0(7) 107.5(6) 108.5(7) 108.9(7) 106. 7 (7) 108.2(6) 126. 8 (7) 124. 4 (7) 125.4(7) 126.8(7) 123.2(7) 127.3(7) 125.5(8) 125.0(8) 124.6(7) 126.9(7) aCpl = C(ll)-C(lS) ring centroid, Cp2 = C(21)-C(25) ring centroid, Cp*l = C(31)-C(35) ring centroid, Cp*2 = C(Sl)-C(SS) ring centroid. 92 Table VI. Least-Squares Planes of Cp, Cp* and Benzene Rings of 7. - Deviation, A Atom • Deviation, A Atom Cpl Ring Cp2 Ring c (11) c (12) c (13) c (14) -0.003 C(21) -0.014 0.009 C(22) 0.015 -0.011 -0.009 C(lS) -0.004 c (23) c (24) c (25) 0.009 0.000 0.008 Cp*2 Ring Cp*l Ring C(31) 0.006 c (51) -0.023 C(32) -0.008 C(52) 0.013 C(33) 0.007 C(53) 0.002 C(34) -0.003 c (54) -0.016 C(35) -0.002 C(SS) 0.024 Benzene Ring c (71) -0.018 C(74) -0.025 C(72) 0.012 c (75) 0. 019 c (73) 0.009 C(76) 0.002 93 Table VII. Crystal and Intensity Data for C~ ZrOCH=C(Zr(I)Cp2 }0 • tCJI 6 • Fonnula Fonnula weight Space group a b c 8 v z Deale Crystal size A µ Scan range Refln settings 26 range, scan rate, and no. of reflns Backgrd time/scan time Total nunber of averaged data Refinement on Final nt.nnber of parameters Final cycle:t R R' s C3zH41IOzZTz·~C6H6 767.02 g/mol P2 1/c 15.866(4) .R 10.673(3) .R 20.561(4) ~ 105.5(2) 0 3361 (1) ~~ 4 1.52 g/cm 3 0.07 x 0.32 x 0.70 rrnn 0.71069 ~ 1. 25 rrnn-l 1.0° above Ka1 , 1.0° below Ka 2 +h, +k, ~l 3<28<30° 3. 91° /min 1250 30<28<45° 2. 02° /min 3450 1.00 4100 F2 0 361 uncorrected * .096(3891) . 084 (3162) 4.44(4100) corrected * .074(3922) .059(3069) 3.12(4100) limited * . 067 (2513) . 054 (1992) 2.93(2691) *Full data set, uncorrected for twinning used in refinement; full data set, corrected iteratively for twinning; limited data set, reflections affected by twinning deleted. tTypical R-value, nt.nnber of reflection used in sums given in parentheses. R' refers to R-value calculated for reflections with F02>30F2. S is the goodness-of-fit; summations include all reflections. 94 Table VIII. Part A. Atomic Coordinations (x 104 ) for C~ZrOCH=C(Zr(I)C1>2)0 · jCJi6 • x I Zr(l) Zr(2) 0(1) 0(2) C(I) C(2) C(ll) C(12) C(13) C(14) C(15) C(21) C(22) C(23) C(24) C(25) C(31) C(32) C(33) C(34) C(35) C(31M) C(32M) C(33M) C(34M) C(35M) C(41) C(42) C(43) C(44) C(45) C(4IM) C(42M) C(43M) C(44M) C(45M) C(3) C(4) C(5) 8334.0(6) 7311.8(7) 8038.7(8) 7928(5) 6311(5) 7468(7) 6583(7) 9588(14) 9326(11) 9034(13) 9216(11) 9586(10) 7026(12) 6522(10) 6586(10) 7210(12) 7494(12) 6765(8) 7419(9) 8238(8) 8079(9) 7197(10) 5873(12) 7292(16) 9069(11) 8763(13) 6752(17) 6670(9) 7560(9) 7908(8) 7200(9) 6425(9) 6011(12) 8077(13) 8813(10) 7296(14) 5537(10) 4305(9) 507 4(10) 5732(9) y 4071.2(8) 5951.6(8) 2480.1(9) 4642(6) 5147(6) 3891(9) 4210(9) 2870(15) 2928(20) 1731(24) 1009(13) 1739(16) 1419(13) 2015(11) 1417(10) 492(11) 496(12) 8036(9) 8361(8) 7913(9) 7344(9) 7 450(10) 8335(14) 9273(11) 8092(19) 6811(13) 7032(14) 6052(9) 6085(10) 4936(11) 4204(9) 4879(11) 7026(13) 7080( 14) 4565(19) 2852(10) 4440(17) -13(12) 654(11) 692(11) z 5237.7( 4) 2294.2( 4) 4073.6( 4) 2941(3) 2628(3) 3252( 4) 3061(5) 4255(10) 3601(10) 3375(7) 3947(10) 4493(7) 4682(7) 4138(6) 3545(6) 37 49(7) 4466(7) 2625(6) 2317(5) 2678(6) 3269(5) 3220(6) 2433(10) 1722(6) 2579(11) 3831(8) 3756(9) 1017(5) 1111(5) 1396(5) 1451(5) 1224( 5) 623(7) 833(6) 1556(7) 1686(6) 1162( 8) 319(6) 586(6) 288(6) 95 - Table VIll. Part B. Gaussian Amplitudes (A2 , x 104 ) for 8. Un I Zr(l) Zr(2) 0(1) 0(2) C(l) C(2) C(ll) C(12) C(13) C(14) C{15) C(21) C(22) C(23) C(24) C(25) C(31) C(32) C(33) C(34) C(35) C(31.M) C(32M) C'(33.M) C(34M) C(35M) C(41) C(42) C(43) C(44) C(45) C(41M) C(42M) C(43M) C(44M) C(45M) C'(3) C(4) C(5) U12 U13 U2a 814(7) -54(5) 577( 5) 447(4) 417(6) -13(5) 199(4) 281(5) 614(7) 75(5) 256( 4) 318(5) 536(53) -13(36) 343(38) 447(40) 438(48) 37(35) 362(39) 478(42) -46(52) 585(77) 290( 49) 299(52) 533(74) -101(52) 299(55) 375(53) 355(113) 1554(207) 665(102) 1575(173) 992(139) 987(148) 1663(182) 1505(173) 814(171) 1074(156) 2286(236) 509(86) 830(123) 604(91) 1530(158) 304(89) 638(85) 434(101) 732(111) 1203(132) 1628(188) 623(87) 688(92) -407(104) 435(65) 488(72) -57(70) 1038(117) 345(63) 677(83) -191(71) 992(121) -208(79) 1429(161) 241(60) 792(92) 1486(173) 455(76) 816(102) -247(93) 191(50) 50(54) 630(87) 722(80) 909(105) 80( 45) 410(60) -125(56) 548(87) 287(57) -211(56) 761(83) 15(64) 259(57) 464(66) 875(108) 1241(134) 262(55) -81(74) 541(70) 856(137) 618(95) 1871(186) 96(93) 37~6(330) 212(67) 535(82) -210(117) 623(121) 1317(155) 2380(228) -450(112) 1886(213) 572(90) 1070(123) 207(110) 3367(320) 657(97) 1400(145) -836(144) 911(108) 322(59) 244(51) 78(65) 693(93) -113(66) 47Q(66) 356(57) 587(85) 308(56) 121( 66) 601(73) 934(107) 278(55) -48(62) 270( 51) 643(92) -146(68) 618(77) 280(56) 1430(159) 449(101) 754(97) 647(91) 2583(235) 824(103) 485(78) -730(124) 520(98) 1800(172) 350(109) 750(94) . 167(59) 2724(247) 490(75) 173(92) 585( 103) 1310(135) -353(98) 992(109) 595(93) 1(70) 575(74) 800(89) 932(122) 628(80) -24(77) 477(72) 660(92) 544(76) -62(68) 592(74) 153(4) 78(4) 118(5) 100(37) 56(35) 125(50) 147(49) 1004(158) 900(141) 140(92) 268(116) 71(76) 604(107) 218(71) 132(78) 108(94) 32(103) 266(67) .11(63) 72(67) -116(67) 536(80) 328(128) 462(133) 551(137) -1072(134) 1888(187) -68(57) 197(57) 139( 54) 213(57) -39(55) -389(94) 874(110) 111(76) 261(108) 214(85) 262(73) 93(81) 44(65) -158(4) -2(4) 27(4) 44(32) 10(33) -33(42) -59(46) -32(108) 1154(150) -413(124) -193(102) 104(89) 47(74) -29(57) 18(60) -70(60) 349(73) -77(51) -14(42) -298(56) -202(51) -191(55) -433(108) 179(58) -1090(159) -145(85) -465(98) -99(46) -46(51) -130(51) -69(44) -221(53) -82(76) -185(71) -355(107) 87(52) -469(103) 114(68) 19(62) 37(62) U22 Uaa 96 Table VIlI. Part C. Hydrogen Coordinates (x 10 ) for ~· 4 H H(ll) H(l2) H{13) H(l4) H(l5) H(21) H(22) H(23) H(24) H(25) H(311) H(312) H(313) H(321) H(322) H(323) H(331) H(332) H(333) H(341) H(342) H(34:3) H(351) H(352) H(353) H(411) H(412) H(413) H(421) H(422) H(423) H(431) H(432) H(433) H(441) H(442) H(443) H(451) H(452) H(453) x y z 6158 3759 3242 9737 3620 4514 9290 3564 3247 8782 1329 2953 9044 101 3984 9818 1472 4942 7065 1625 5140 6177 2781 4151 6227 1604 3092 7415 -73 3442 7881 -55 4738 5544 8812 1948 5503 8958 2692 5313 7643 2337 7842 9905 1652 7171 8974 1187 6830 10030 1589 9600 7410 2644 9568 8826 2813 9190 8401 2072 9499 7056 3947 8962 5809 3882 8801 6867 4369 7071 6186 4123 6733 7563 4204 6140 6593 3693 6311 7566 367 5800 7520 932 5527 6602 329 8539 7430 1219 8356 6700 526 7693 7773 659 9327 4863 2002 9265 4711 1232 9049 3566 1650 7891 2490 2058 7309 2034 1370 6873 2358 1952 5324 3955 1574 5190 3703 814 4937 5002 1048 97 - Table IX. Bond Distances (A) in 8. zT CJ. ) .. 0 Cl ) Zr (l) ... Q(2) 0 (1) -C(l) 0 (.2) -c (2) C(1)-C(2) C (1)-ZT (2) ZT(2)-I Zr (2)-C (11) Zr ( 2) - C (12) Zr (2) .. c (13) Zr (2) -C (14) Zr ( 2) - C (1 5) Zr (. 2 ) - Cp (1 ) a c (11) ... c (12) c (12) ... c (13) c (13) ... c (14) c (.14 ) - c (1 5 ) C(15)·C(11) Zr ( 2) -C (.21) Zr (2) -C C.22) Zr(2)-C(23) Zr(.2)-C[24) Zr [2) --C (25) Zr ( 2) - Cp ( 2) a C(21)-C(22) C(.22)-C(23) c (23) ... c (24) c (24) -c (25) c (2 s) -c (21 ) Zr(l)-C(31) Zr(l)-C(32) Zr (1) -C (33) 1. 999 (.7) 2. OT3 (7) 1. 352 (.12) 1. 333 (12) 1. 402 (14) 2. 268 (1 O) 2. 8 7 2 (1) 2.42(2) 2.52(2) 2.53(2) 2. 51 (2) 2. 51 (.2) 2. 218 1.31(3) 1. 38 (3) 1.38(3) 1.37(2) 1. 30 (2) 2.55(2) 2. 49 (1) 2.55(1). 2. 5 0 (1) 2.50(2) 2.223 1.35(2) 1.40(2) 1.39(2) 1.43(2) 1.38(2) 2.54(1) 2.58(1) 2.56(1) Zr(l)-C(34) Zr(l)-C(35) Zr (1) - Cp * (1) a c (31) -c (32) C(32)-C(33) C(33)-C(34) C(34)-C(35) c (3 5) - c (31) C(31)-C(31M) C(32)-C(32M) C(33)-C(33M) C(34)-C(34M) C(35)-C(35M) Zr(l)-C(41) Zr(l)-C(42) Zr(l)-C(43) Zr(l)-C(44) Zr(l)-C(45) ·a Zr ( 1 ) - Cp * (2 ) C(41)-C(42) C(42)-C(43) C(43)-C(44) C(44)-C(45) C(45)-C(41) C(41)-C(41M) C(42)-C(42M) C(43)-C(43M) C(44)-C(44M) C(45)-C(45M) C(3)-C(4) C(4)-C(5) C(S)-C(3)' 2.53(1) 2.53(1) 2.254 1.39(2) 1.40(2) 1.44(2) 1.38(2) 1.39(2) 1.40(2) 1.54(2) 1.40(2) 1.47(2) 1.52(2) 2.56(1) 2.57(1) 2.53(1) 2. 5 2 (1) 2.55(1) 2.254 1.39(2) 1.41(2) 1.40(2) 1.39(2) 1.41(2) 1.56(2) 1.55(2) 1.44(2) 1.52(2) 1.46(2) 1.40(2) 1.34(2) 1.43(2) aCp(l) = C(ll)-C(15) ring centroid, Cp(2) = C(21)-C(25) ring centroid, Cp*(l) = C(31)-C(35) ring centroid, Cp*(2) = C(41)-C(45) ring centroid. 98 - Table X. Bond Angles (deg) in 8. zr C1 ) - o Cl ) - c C1 ) 0 (1) - c (1 ) - 0 ( 2) c (1) -c (2) -0 ( 2) C(2)-0(2)-Zr(l) 0 ( 2) - Zr (1) -0 (1) 0(1)-C(l)-Zr(2) C(2)-C(l)-Zr(2) C(l)-Zr(2)-I Cp*l-Zr(1)-Cp*2a Cpl-Zr(2)-Cp2a c (11) - c (12) - c (13) C(12)-C(13)-C(14) C(13)-C(14)-C(15) C(14)-C(15)-C(ll) C(15)-C (11)-C (12) C(21)-C(22)-C(23) C(22)-C(23)-C(24) C(23)-C(24)-C(25) C(24)-C(25)-C(21) C(25)-C(21)-C(22) C(31)-C(32)-C(33) C(32)-C(33)-C(34) C(33)-C(34)-C(35) C(34)-C(35)-C(31) C(35)-C(31)-C(32) 120. 0 (6) 110.4(9) 119.5(9) 113.1(6) 76.9(3) 126.0(7) 123.1 (7) 100.1 (3) 136.9 128.9 107 (2) 105(2) 109 (2) 105 (2) 113 (2) 110 (1) 106 (1) 109 (1) 107 (1) 109 (1) 112(1) 104 (1) 108 (1) 111 (1) 105(1) C(35)-C(31)-C(31M) C(32)-C(31)-C(31M) C(31)-C(32)-C(32M) C(33)-C(32)-C(32M) C(32)-C(33)-C(33M) C(34) -C (33) -C (33M) C(33)-C(34)-C(34'M) C(35) -C (34) -C (34M) C(34)-C(35)-C(35M) C(31)-C(35)-C(35M) C(41)-C(42)-C(43) C(42)-C(43)-C(44) C(43)-C(44)-C(45) C(44)-C(45)-C(41) C(45)-C(41)-C(42) C(45)-C(41)-C(41M) C(42)-C(41)-C(41M) C(41)-C(42)-C(42M) C(43)-C(42)-C(42M) C(42)-C(43)-C(43M) C(44)-C(43)-C(43M) C(43)-C(44)-C(44M) C(45)-C(44)-C(44M) C(44)-C(45)-C(4SM) C(41)-C(45)-C(4SM) 129 (1) 125 (1) 124 (1) 12 3 (1) 131 (1) 124 (1) 124 (1) 12 8 (1) 12 5 (1) 124 (1) 108 (1) 106 (1) 110 (1) 106 (1) 110(1) 124(1) 12 6 (1) 126(1) 124(1) 126 (1) 127 (1) 123(1) 12 7 (1) 128 (1) 127(1) aCpl = C(ll)-C(lS) ring centroid, Cp2 = C(21)-C(25) ring centroid, Cp*l = C(31)-C(35) ring centroid, Cp*2 = C(41)-C(45) ring centroid. 99 Table XI. Least-Squares Planes of Enediolate Metallocycle, - Cp and Cp* Rings of 8. a Atom Zr (1) Zr (2) 0 (1) Deviation, A Atom Enediolate Metallocycle 0.035 0(2) c (1) 0.058 c (2) -0.026 Deviation, A 0.038 -0.071 -0.034 Cpl Ring C(ll) -0. 034 c (12) 0.029 c (13) -0.014 c (14) -0.004 0.023 c (15) Cp2 Ring C(21) -0.027 0.032 c (22) -0.023 C(23) 0.007 C(24) 0.012 c (25) Cp*l Ring 0.022 C(31) C(32) -0.024 c (33) 0.016 C(34) -0.002 C(35) -0.012 C(31M) -0.035 -0.308 C(32M) -0.099 C(33M) -0.066 C(34M) C(35M) -0.101 Cp*2 Ring C(41) 0.005 -0.009 c (42) 0.009 C(43) -0.006 C(44) 0.001 c (45) -0.217 C(41M) -0.264 C(42M) -0.036 C(43M) -0.102 C(44M) -0.085 C(4SM) aA positive deviation is a deviation toward the metal atom. 100 Table XII. Cross-Over Experiment. 0.263 mrnol (99% 12 c) 0.176 mrnol (91% 13 c) l 12c12c calculated .59 observed .58 5 + 5 % Cross-over 0.422 mrnol 101 General Considerations: All manipulations were performed under an inert atmosphere by employing a nitrogen-filled glove box and vacuum-line techniques. Hydrogen, nitrogen and argon were purified by passing through MnO on vermiculite 37 and activated 4A molecular sieves. Benzene, toluene and pet ether (30"-60"), including NMR solvents, were vacuum transferred from LiAlH 4 or molecular sieves, then from "titanocene" 38 prior to use. Pyridine and methyl iodide were vacuum transferred from CaH2 ; <is-pyridine and acetone were transferred from 4 A molecular sieves. 13 Carbon monoxide (MCB), C-carbon monoxide (Monsanto-Mound) and PMe3 (Strem) were used as received. Cp2 Zr(C0) 2 , 32 Cp2 Zr(CO)(PMe 3 ) 27 and cp:zrH2 1b were prepared by literature methods. Cp2 Zr( 13 C0) 2 was made by photolysis of Cp2 Zr(C0) 2 under a 13 CO atmosphere. cp;zrD2 was prepared by treatment of [cp:ZrN2 ] 2 N2 with D2 at low temperature and used promptly. 1 H NMR spectra were recorded using C6 D6 , C7 D8 or C5 D5 N as solvent with TMS as an internal reference using Varian EM-390, JOEL FX90Q and Bruker WM-500 spectrometers. obtained using the JOEL instrument. 13 C NMR spectra were m spectra were recorded as nujol mulls on a Beckmann IR 4240 spectrophotomer. Elemental analyses were performed by Alfred Bernhardt Analytical Laboratory and Dornis and Kolbe Microanalytical Laboratory. At -196e C 20 ml toluene was added to a mixture of CpZr(CO)(PMe 3 } (1. 30 g, 102 4. 00 mmol) and cp:zrH2 (1. 45 g, 4. 00 mmol). The solution was stirred at -78°C for 30 minutes to react, then warmed to room temperature. After filtration the solution was concentrated to 10 ml and 15 ml pet ether added to precipitate the red crystalline product. Cp2 (PMe3 )Zr=CHO-Zr(H)Cpi (2. 30 g, 84%) was isolated by filtration and washed with cold pet ether. Anal. Calcd for C34H510PZr2 : C, 59.25;H, 7.46;0, 2.32;P, 4.49;Zr, 26.47. Found:C, 58 .• 69; H, 7. 36; Zr, 26. 79. JR (nujol mull): 2755 w, 1560 w, 1280 w, 1100 s, 950 m, 775 m. Cp2 (PMe3 )Zr=CDO-Zr(D)Cpi was prepared in a similar manner using C1>2Zr(CO)(PMe3 ) and cp:zr~. IR (nujol mull): 2045 vw, 1580 w, 1280 w, 1100 s, 950 m, 775 m. Cp2 (CO)Zr=CHO-Zr(H)Cp: (_ID. A pet ether solution of C~ZrH2 (250 mg, O. 69 mmol) was slowly added to a pet ether solution of C1>2Zr(C0) 2 (210 mg, O. 76 mmol) at ca. -10• C, resulting in an immediate color change from dark green to red. The solution was concentrated and cooled to -78• C to precipitate the product as a tan solid. C1>2(CO)Zr=CHO-Zr(H)Cp: (230 mg, 53%) was isolated by filtration at -78° C, washed with cold pet ether, and dried in vacuo. Due to the - instability of 4 in solution recrystallization proved impossible. IR (nujol mull): 2755 w, 1925 vs, 1620 w, 1515 w, 1170 s, 1155 s, 1005 w, 780 m. Cp2 (CO)Zr=CD0-Zr(D)Cp: was prepared by using Cp2 Zr(C0) 2 and Cp:zr~. IR (Nujol mull): 2042 w, 1925 vs, 1570 w, 1170 s, 1155s, 1005 w, 780 m. [Cp2 Zr(C 2H20 2 )ZrCpilx (~). A mixture of CP2Zr(C0) 2 (190 mg, 0. 69 mmol) and CptZrH 2 (250 mg, 0. 69 mmol) was dissolved in 15 ml 103 benzene and stirred a room temperature for 10 hr. The insoluble, yellow product precipitated from the reaction solution. ........ 6 (115 mg, 25%) was isolated by filtration and washed with copious amounts of pet ether. Anal. Calcd. for C32H420 2 Zr2 : C, 59.95; H, 6.60; O, 4.99; Zr, 28.46. Found: C, 59. 82; H, 6. 68. m (nujol mull): 1552 w, 1527 s, 1318 w, 1120 s, 1012 m, 967 w, 858 m, 794 s, 782 sh. Cp2 Zr(C2 H4 0 2 )(Zrcp:) 2 (~). Toluene was condensed onto Cp2 Zr(C0) 2 (81 mg, O. 29 mmol) and cp;zrH 2 (202 mg, O. 56 mmol) at -196° C and warmed to room temperature. The solution lightened from the dark red color of ........ 5 to light orange after ca. 10 minutes. The light yellow product (145 mg, 50%) was isolated by concentration, addition of pet ether and filtration at -78eC. IR (nujol mull): 1570 w, br, 1519 s, 1225 m, 1052 m, 1020 w, 790 m, 728 w, 696 s, 680 s. Cp2 (PMe3 ) Zr=CHO-Zr(I)Cp: (:l). Cp2 (PMe3 ) Zr=CHO-Zr(H)Cp: (1. 50 g, 2.18 mmol) was dissolved in 30 ml toluene. Methyl iodide (2.18 mmol), premeasured in a calibrated volume, was condensed into the reaction flask at -78° C. The solution was stirred at room temperature for 30 minutes to effect reaction, indicated by a color change from red to green. The toluene was removed to yield the green crystalline product. Cp2 (PMe 3 ) Zr=CHO-Zr(I)Cp: (1. 48 g, 83%) was washed with ca. 40 ml pet ether at -78e C and isolated by filtration. Anal. Calcd for C34H 50 IOPZr2 : C, 50.10; H, 6.18; I, 15. 57; 0, 1. 96; P, 3.80; Zr, 22.38. Found: C, 49.84; H, 5.97; I, 15.86; P, 3.63. IR (nujol mull): 2725 vw, 1280 w, 1075 s, 950 m, 780 m. Cp2 (PMe3 )Zr=CDO-Zr(I)Cp; was prepared in a similar manner from Cp2 (PMe 3 )Zr=CDO-Zr(D)Cp; and Mel. IR (nujol mull): 2020 vw, 104 1280 w, 1075 s, 950 m, 780 m. C~ZrO-CH=C(Zr(I)Cp:)o (ID. Toluene (25 ml) was condensed onto a mixture of C1>2Zr(C0) 2 (0. 83 g, 3. 00 mmol) and C~ZrH 2 (1. 07 g, 3. 00 mmol) at -196• C and then warmed to o• for ca. 5 minutes to - effect formation of 5. The reaction mixture was re-cooled to -196• C and Mel (13 mmol) was added. On stirring for 3-! hr at room temperature the solution turned purple. On concentration of the toluene and addition of pet ether a dark purple solid was obtained. C~ZrO-CH=C(Zr(I)CP.a)O (1. 38 g, 60%) was recrystallized from benzene. The above procedure was carried out employing a mixture of 13 C1>2Zr(C0)2 (73 mg, 0. 263 mmol) and Cp2 Z1'( C0) 2 (49 mg, 0.176 mmol) 91 ± 3% 13 C enriched). The 13 C NMR spectrum of the resulting product 13 - showed a ratio 8 {1 3 C, C)/8 {1 2 C, 13 C) of 3. 2± 0.4. Using this ratio and - 13 . the initial amounts of CP,aZr(C0)2 and CP,aZr( C0) 2 the calculated - C) ratios were determined and are tabulated in Table XIl. The difference (no isotopic cross-over) and actual 8 ( 12C, 12 12 C): 8 ( C, 13 13 C): 8 ( C, 13 - corresponds 5 ± 5% isotopic cross-over on the formation of 8. In an alternative synthesis of !!_, a benzene solution of C1>2(PMe 3 )Zr=CHO-Zr(I)C~ (710 mg, O. 87 mmol) was stirred under 200 Torr CO for 3j hr at room temperature. Longer reaction times - or higher CO pressures led to a diminished yield of 8 due to further reaction. Removal of solvent and liberated PMe3 in vacuo, washing with cold pet ether and recrystallization from benzene to remove ·unreacted 1 gave C~ZrO-CH=C(Zr(I)Cp2 )6 in ca. 30% yield. Anal. 105 Calcd for C32H41 I0 2 Zr2 : C, 50.11; H, 5. 39; I, 16. 55; 0, 4.17; Zr, 23. 79. Found: C, 50. 34; H, 5. 38; I, 16. 38. m (C 6 D6 ): 1433 m, 1380 w, 1250 m, 1120 w, 1020 w, 800 m. Cp2 (pyr)Zr(O=C=CHO-Zr(H)Cp:) (!!). At -196° C 15 ml pyridine was condensed onto a mixture of Cp2 Zr(C0) 2 (425 mg, 1. 53 mmol) and cp:ZrH 2 (550 mg, 1. 52 mmol). The solution was stirred at room temperature for 1 hr. Concentration of the solution to ca. 1 ml and addition of pet ether gave orange crystals. Cp2 (pyr)Zr(O=C=CHO-Zr(H)Cp;) (890 mg, 82%) was isolated by filtration, washed with cold pet ether and dried in vacuo. Anal. Calcd for C37 H47 N0 2 Zr2 : C, 61. 68; H, 6. 58; N, 1. 95; 0, 4. 45; Zr, 25. 34. Found: C, 61. 73; H, 6. 91; N, 1. 96. IR (nujol mull): 1600 m, 1518 w, 1216 w, 1110 s, 1008 m, 831 w, 788 s. 13 Cp2 (pyr)Zr(0=13 C= CHO-Zr(H)Cp:) was prepared by using Cp2 Zr(1 3 C0) 2 (70% 13 C enriched) in place of Cp2 Zr(C0) 2 in the above procedure. Cp2 (pyr)Zr(O=C=CHO-Zr(I)Cp: (1.Q). ~ CH 3 I (0. 061 mmol) was added to a NMR sample tube of ~ (40 mg, O. 056 mmol) in C 5 D5 N at -196° C, which was sealed. On warming to room temperature the 1H NMR spectrum showed !.Q. In a separate experiment CH 3 I (0.134 mmol) was added to~ (92 mg, 0.128 mmol) in pyridine at -196° C and warmed to room temperature for 30 minutes; upon completion of the reaction 0.113 mmol CH 4 (0. 88 equivalents CH 4 /equivalent ~) were recovered by Toepler pump. AnNJMR sample of 9 (20 mg, 0. 028 mmol) and """ 1 CH 3 I (0.14 mmol) is C 6 D6 gives an H NMR spectra identical to that obtained for§_ in C6 D6 with one equivalent of pyridine. Likewise, a 106 sample of!!, dissolved in C5 D5 N, has the same spectrum as 1Q prepared from 9. """ Structure Determination for Cp2 (PMe3 )Zr=CHO-Zr(I)Cp:. A large single crystal was mounted approximately along the c-axis- in a glass capillary under N2 • A series of oscillation and Weissenberg photographs indicated monoclinic symmetry and a centered lattice, and our initial choice of axes conformed to I2/a (hkl absent for h+k+l odd, hOl absent for h odd); data were collected on a locally-modified Syntex P2 1 diffractometer with this cell. To be consistent with space group C2/c, all reflection indices were transformed for the subsequent calculations (h' = h+l, l'.= -h). The lattice constants reported in Table 1 were obtained by least-squares refinement of thirty 28 values (25 < 28 < 44°), where each 29 value was an average of two measurements at ±28. The three check reflections indicated no decomposition 2 and the data were reduced to F 0 ; the form factors for all atoms were taken from reference 39, and those for Zr and I were corrected for anomalous dispersion. The details on unit cell parameters and data collection are given in Table II. The positions of the Zr and I atoms were derived from the Patterson map, and the Fourier map phased on these three atoms revealed the remaining non-hydrogen atoms of the Zr complex. Leastsquares refinement of atomic coordinates and U's, minimizing LW [ F ~0 -(F c I k) 212 gave RF = 0.131. A molecule of benzene and all hydrogen atoms were located from difference maps. The benzene molecule is apparently ordered and the coordinates of the carbon atoms were refined; all hydrogen atoms except H( 4) were introduced into the 107 model with fixed coordinates and isotropic B's. The refinement of all non-hydrogen atoms in the Zr-complex with anisotropic U's, carbon atoms in the benzene molecule with isotropic B's, and the carbene hydrogen atom H(4) using all the data (8169 reflections) led to RF = O. 082; the scale factor and Gaussian amplitudes in one block and the coordinates in the other. A number of reflections had large weighted residuals, and examination of the diffractometer data indicated that most of these reflections had unusual backgrounds or scans; these 208 reflect ions were deleted before the final eye le of refinement. All calculations were carried out on a VAX 11 /780 using the CRYM system of programs. Structure Determination for Cp*zr-OCH=C(Zr(I)C crystals were mounted in glass capillaries under N2 • Oscillation, Weissenberg, and precession photographs indicated a monoclinic lattice, space group P2 1 /c (OkO absent for k odd, hOl absent for 1 odd), and twinning by reticular pseudo-merohedry across the ab-plane with a twin index of 3: the h, k, -l-2h/3 reflections of the twin lattice were superimposed onto the h, k, 1 reflections of the parent lattice. (The metric relation between a, c, and (3 is 3ccos,B = -a.) The twin fraction varied with each crystal, indicating macroscopic twin domains. One of these crystals was selected for data collection on a locally modified Syntex P2 1 diffractometer; details on unit cell parameters and the data collection are given in Table VIII. The three check reflections indicated no decomposition and the data were reduced to F~ . The positions of the Zr and I atoms were derived from a Patterson map, and an electron density Fourier map phased on these 108 three atoms revealed the remaining non-hydrogen atoms of the Zrcomplex and a benzene molecule of crystallization. Least-squares refinement of atomic coordinates and U's minimizing L;w [~ -(F c/k) ] gave RF = 0.144; 40 the form factors for all atoms were taken from 2 2 reference. 39 ..· The hydrogen atoms were then located from difference maps and introduces into the model with fixed coordinates and isotropic B's. The refinement of non-hydrogen atoms with anisotropic U's using all the data (4100 reflections) led to RF = O. 096, RF = O. 084, and S = 4.44. At this stage, the F~ were corrected for twinning in an iterative manner by subtracting off an estimate of the twin contribution to the intensity. 41 This led to an improved data set, as evident from the lower goodness-of-fit: S = 3. 04 (RF = 0. 074, RF = 0. 059). After another cycle of least-squares refinement, the F~ data were corrected again, but the correction differed marginally from the first pass: the volume ratio of the twins was 0.19:1; the final results are indicated in Table 1. The remaining errors in the data appear to be normally distributed. To check this, we carried out a paralle 1 refinement in which all affected reflections were deleted. Refinement with this data set led to coordinates and U's that were insignificantly different (within 2a) from the starting set; the goodness-of-fit (2. 93, 2691 reflections total) is essentially the same as from the full data set refinement, and indicates that the twin correction is adequate (RF = 0. 067, RF = 0. 054). A 11 results quoted hereafter refer to refinement with the full data set. 109 References ~ 1. (a) Manriquez, J. M.; McAlister, D. R.; Sanner, R. D.; -(b) Manriquez, J. M.; McAlister, D. R.; Sanner, R. D.; Bercaw, J. E. J. Amer. Chem. Soc. 98, 6733 (1976); Bercaw, J. E. J. Amer. Chem. Soc. !QQ, 2716 (1978); (c) Bercaw, J. E. Adv. Chem. Ser. No. 167, 136 (1978); ~ (d) Wolczanski, P. T.; Bercaw, J. E. Acc. Chem. Res. ............. 13, 121 (1980). 2. Threlkel, R. S.; Bercaw, J. E. J. Amer. Chem. Soc. 103, ~ 2850 (1981). 3. Wolczanski, P. T.; Threlkel, R. S.; Bercaw, J. E. J. Amer. Chem. Soc. 101, 218 (1979). ~ 4. Chapter I of this thesis. 5. Fryzuk, M. D.; Bercaw, J. E.; unpublished results. 6. Schwartz, J.; Gell, K. I. J. Organomet. Chem. !_!!1, Cl (1980). 7. Hartner, F. W.; Schwartz, J.; Clift, S. M. J. Amer. Chem. Soc. W, 641 (1983). 8. -- (a) Heck, R. F.; Breslow, D. S. J. Amer. Chem. Soc. 83, 4023 (1961); (b) Calderazzo, F. Angew. Chem. Int. Ed. Engl. !.§_, 299 (1977). 9. (a) Cossee, P. J. Catalysis ~' 80 (1964); (b) Cossee, P. Rec. Trav. Chim., Pays-Bas §.§_, 1151 (1966); (c) Henrici-Olive, G.; Olive, S. Fortschr. Chem. Forsch. i7, 107 (1976). 10. (a) Fischer, F.; Tropsch, H. Brennst.-Chem. J, 97 (1926); -- Chem. Ber. 59, 830 (1926); 110 (b) Brady, R. C., III; Pettit, R. J. J. Amer. Chem. Soc. 102, ~ 6181 (1980); ibid. ~' 1287 (1981). -- 11. RUchardt, C.; Schrauzer, G. N. Chem. Ber. 93, 1840 (1960). 12. Dorrer, B. ; Fischer, E. 0. Chem. Ber. 107, 2683 (1974). 13. Messer le, L.; Curtis, M. D. J. Amer. Chem. Soc. ]jg, 7791 ~ (1980). 14. Messer le,. L.; Ph.D. Thesis, Massachusetts Institute of Technology, 19 79. 15. Roper, W. R.; A bst. of Amer. Chem. Soc. Nat. Meet., Kansas City, Mo., September 5-10, 1982. 16. (a) Herrmann, W. A.; Plank, J. Angew. Chem. Int. Ed. Engl. 17, ,,..,_,... 525 (1978); (b) Herrmann, W. A.; Plank, J. ; Ziegler, M. L.; Weidenhammer, K. J. Amer. Chem. Soc. 101, 3133 (1979). ~ 17. stevens, A. E.; Beauchamp, J. L. J. Amer. Chem. Soc. 100, ~ 2584 (1978). 18. The 1 H NMR spectrum of Cp:Zr(OCH 3 )I has not been reported; it is (C 6D6 , 34 e C) 1. 86 o (s, Cp*), 3. 67 o (s, OCH3 ). 19. (a) Sanner, R. D.; Manriquez, J. M.; Marsh, R. E.; Bercaw, J. E. J. Amer. Chem. Soc. ,,..,_,... 98, 8351 (1976); (b) McKenzie, T. C.; Sanner, R. D.; Bercaw, J.E. J. Organomet. Chem. 102, 457 (1975); ~ (c) Lappert, M. F.; Martin, T. R.; Atwood, J. L.; Hunter, W. E. J. Chem. Soc., Chem. Commum., 522 (1976). (d) Jeffery, J.; Lappert, M. F.; Luong-Thi, N. T.; Webb, M.; Atwood, J. L. ; Hunter, W. E. J. Chem. Soc. , Dalton Trans. , 1593 (1981). 111 (e) Fachinetti, G.; Fochi, G.; Floriani, C. ibid., 1946 (1977); (f) Hunter, W. E. ; Atwood, J. L. ; Fachinetti, G. ; Floriani, C. J. Organomet. Chem. W, 67 (1981). 20. Atwood, J. L.; Hunter, W. E.; Hrncir, D. C.; Samiel, E.; Alt, H.; Rausch, M. D. Inorg. Chem. 11., 1757 (1975). 21. Jeffrey, J. ; Lappert, M. F. ; Luong-Thi, N. T. ; Atwood, J. L. ; Hunter, W. E. J. Chem. Soc., Chem. Commum. 1081 (1978). 22. (a) Cardin, D. J.; Cetinkaya, B.; Lappert, M. F. Chem. Rev. 72, 575 (1972); """"' (b) Cotton, F. A.; Lukehart, C. M.; Prag. Inorg. Chem. li, 243 (1972). 23. (a) Silverton, J. V.; Hoard, J. L. Inorg. Chem. ~' 243 (1963); (b) 5tezowski, J. J.; Eick, H. A. J. Amer. Chem. Soc. 91, ./"'-" 2890 (1969); (c) Von Dreele, R. B.; Stezowski, J. J.; Fay, R. C. J. Amer. Chem. Soc. ~' 2887 (1971); (d) Elder, M. Inorg. Chem. !!, 2103 (1969); (e) Chun, H.K.; Steffan, W. L.; Fay, R. C. Inorg. Chem.]&, 2458 (1979). 24. (a) Clarke, J. F.; Drew, M. G. B. Acta Cryst. ~' 2267 (1974); (b) Petersen, J. L. J. Organomet. Chem. W, 179 (1979). 25. (a) Dunitz, J. D. "X-Ray Analysis and the Structure of Organic Molecules"; Cornell University Press: Ithaca, NY, 1979; p. 338; (b) "Interatomic Distances, Supplement", Sutton, L. E. , Ed. ; Special Publication No. 18, The Chemical Society: London, 1965. 112 26.. (a) Straus, D . A . ; Ph . D. Thesis, California Institute of Technology, 1983; (b) Moore, E . J.; straus, D. A . ; Armantrout, J.; Santarsiero, B. D.; Grubbs, R.H.; Bercaw, J.E. J. Amer. Chem. Soc., manuscript accepted for publication. 27. Demerseman, B.; Bouquet, G.; Bigorgne, M. J. Organomet. Chem. 132, 223 (1977). ~ 28. Brown, F. J. Prog. Inorg. Chem. ll, 1 (1980). 29. (a) Schrock, R. R.; Sharp, P. R. J. Amer. Chem. Soc. 100, ~ 2389 (1978); (b) Schrock, R. R. Acc. Chem. Res. -""-"' 12, 98 (1979). 30. Calabro, D. C.; Lichtenberger, D. L.; Herrmann, W. A. J. Amer. Chem. Soc. 103, 6852 (1981). ~ 31. Schrock has argued that early metal alkylidene ligands, such as methylene in Cp2 Ta(CH 2 )(CH 3 ), should be considered as 7T-donors to the metal center since the carbene 'TT-orbital is probably lower in energy that the metal orbitals, similar to the energy ordering of the metal and oxygen 7T-orbitals in metal oxo complexes. 29 b 32. Demerseman, B.; Bouquet, G.; Bigorgne, M. J. Organomet. Chem. 107, C19 (1976). ~ 33. Wood, C. D.; McLain, S. J.; Schrock, R. R. J. Amer. Chem. Soc. lQ!, 3210 (1979). 113 34. (a) Manriquez, J. M.; McAlister, D. R.; Sanner, R. D.; Bercaw, J. E. J. Amer. Chem. Soc. 100, 2716 (1978); ~ (b) Straus, D. A.; Buchwald, S.; Grubbs, R. H.; manuscript in preparation. 35. Lauber, J. W.; Hoffmann, R. J. Amer. Chem. Soc. ~' 1729 (1976). 36. (a) Ben-Shoshan, R.; Pettit, R. J. Amer. Chem. Soc. 89, 2231 """" (1967); (b) Foxman, B.; Marten, D.; Rosan, A. ; Raghu, S.; Rosenblum, M. ibid. ~' 2160 (1977). 37. Brown, T. L.; Dickerhof, D. W.; Bafus, D. A.; Morgan, G. L. Rev. Sci. Instrum. 33, 491 (1962). "'"""" 38. Marvich, R. H.; Brintzinger, H. H. J. Amer. Chem. Soc. 93, """" 2046 (1971). 39. International Tables for X-ray Crystallography, Vol. IV, pp. 72-98 (1974). 40. RF = ~ 11F 0 1- l F c IlI~ l F I, sums include only those reflections with F~ > O. 0 RF = RF, but the sums include only those reflec2 tions with F~ > 3aF2. S = [:Ew(F~ - F~) /(n - p)] ~, where n =total number of reflections and p = total number of parameters in the least-squares refinement. 41. The twin fraction o is defined by the relation (kF0 ) 2 = F~p + <SF~T' where k is the scale factor (estimated from the reflections unaffected by the twinning), F 0 is the observed structure factor amplitude of the parent reflection, F cP is the F c of the parent reflection, and F cT is the F c of the twin reflection. The least- 114 squares solution for ~ gives o = [k ~w~F~T - ~wF~pF~T] I 2 ~w~T; the weight w is the least-squares weight for the twin reflection. The corrected F~ is then calculated: (kF~} (kF 0 ) 2 - 2 = 5F~T' and used in the next cycle of least-squares refinement of coordinates and U's.