Synthesis, Structure, and Reactivity of Hydride and Phosphide Complexes of Hafnium and Zirconium Citation Roddick, Dean Michael (1984) Synthesis, Structure, and Reactivity of Hydride and Phosphide Complexes of Hafnium and Zirconium. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/wbgr-yd42. https://resolver.caltech.edu/CaltechTHESIS:10222018-111603289 Abstract A series of alkyl hydride complexes Cp * 2 Hf(H)R (R=Et, CH 2 CHMe 2 , CH 2 CH 2 Ph; Cp * = η-C 5 Me 5 ) have been prepared by reaction of Cp * 2 HfH 2 with the appropriate olefin. The reactions of these compounds with H 2 and C 2 H 4 follow those of the previously reported zirconium isobutyl hydride, Cp * 2 Zr-(H)CH 2 CHMe 2 , giving Cp * 2 HfH 2 and metallacyclopentane Cp * 2 Hf-CH 2 CH 2 CH 2 CH 2 , respectively, plus one equivalent alkane. All alkyl hydrides examined exhibit high thermal stability and decompose only slowly at 80°C. The thermolysis of Cp * 2 Hf(H)CH 2 CHMe 2 yields a 1:1 mixture of Cp * 2 HfH 2 and a metallacyclobutane complex Cp * 2 HfCH 2 CH(Me)CH 2 . A proposed mechanism for the formation of Cp * 2 HfCH 2 CH(Me)CH 2 is given, involving initial γ-H abstraction from the isobutyl methyls of Cp * 2 Hf(H)CH 2 CHMe 2 . Cp * 2 HfH 2 also reacts cleanly with t -butylacetylene to form a remarkably stable alkenyl hydride complex, Cp * 2 Hf(H)CH=CH t Bu. The reactivity of Cp * 2 Hf(H)CH=CH t Bu with H 2 and C 2 H 4 is similar to that observed for the related alkyl hydrides. The hydride complexes Cp * 2 Hf(H)Ph and Cp * 2 Hf-(H)CH 2 CMe 3 have been conveniently prepared by the metathesis of Cp * 2 HfH 2 with PhLi and LiCH 2 CMe 3 , respectively. Cp * 2 HfH 2 reacts cleanly with allene to form the π-allyl hydride Cp * 2 Hf(H)(η 3 -CH 2 CHCH 2 ). 1 H and 13 C NMR data as well as labeling studies indicate that Cp * 2 Hf(H)(η 3 -CH 2 CHCH 2 ) is highly fluxional, and isostructural to Cp * 2 Zr(H)(η 3 -CH 2 CHCH 2 ). The crystal structure of Cp * 2 Hf(H)(η 3 -CH 2 CHCH 2 ) is presented. The coordination of the allyl ligand is confirmed to be trihapto, with notably asymmetric Hf-C(allyl) distances (2.38, 2.48, 2.57 A). The final R index is 0.049. The hydride ligand has been reliably located, and represents the first structurally characterized example of a terminal Hf-H bond. Cp * 2 Zr(H)CH 2 CHMe 2 has been shown to react cleanly with CO to form the enolate hydride Cp * 2 Zr(H)OCH=CHCHMe 2 . A proposed mechanism for formation of Cp * 2 Zr(H)OCH=CHCHMe 2 involves hydride migration via the initially formed acyl hydride Cp * 2 Zr(H)(η 2 -C(O)CH 2 CHMe 2 ) to give a π-coordinated aldehyde complex Cp * 2 Zr(η 2 -OCHCH 2 CHMe 2 ), which subsequently β-H eliminates to give the observed product. Support for the intermediacy of a π-aldehyde complex in this transformation is provided by the reaction of Cp * 2 M(H)CH 2 CHMe 2 (M=Zr, Hf) with excess CO under controlled conditions to give moderately stable π-aldehyde carbonyl complexes Cp * 2 M(CO)(η 2 -OCHCH 2 CHMe 2 ). Thermolysis of Cp * 2 Hf(CO)(η 2 -OCHCH 2 CHMe 2 ) results in a novel coupling reaction to form the enediolate Cp * 2 HfOC(CH 2 CHMe 2 )CHO. The coordinatively unsaturated zirconium π-aldehyde intermediate Cp * 2 Zr(η 2 -OHCCH 2 -CHMe 2 ) is also implicated in the reactions of acyl hydride Cp * 2 Zr(H)(η 2 -C(O)CH 2 CHMe 2 ) with trapping substrates C 2 H 4 , MeC≡CMe, H 2 , and HC≡C t Bu upon warming to give Cp * 2 Zr(OCH(-CH 2 CHMe 2 )CH 2 CH 2 ), Cp * 2 Zr(OCH(CH 2 CHMe 2 )C(Me)=C(Me)), Cp * 2 Zr-(H)OCH 2 CH 2 CHMe 2 , and Cp * 2 Zr(C≡C t Bu)OCH 2 CH 2 CHMe 2 , respectively. Carbonylation of the alkenyl hydride Cp * 2 Hf(H)CH=CH t Bu did not yield an aldehyde complex, but rather the metallacycle Cp * 2 Hf(OHC=CHCH( t Bu)). Mechanistic interpretations of these and related reactions are presented. A series of mono-ring, terminal phosphide complexes of hafnium have been prepared. Reaction of Cp * HfCl 3 with one equivalent or excess LiP t Bu 2 yields deeply-colored phosphide complexes Cp*HfCl 2 (P t Bu 2 ) and Cp*HfCl(P t Bu 2 ) 2 , respectively. Alkyl and aryl derivatives of Cp*HfCl 2 (P t Bu 2 ), Cp*HfR(Y)(P t Bu 2 ) (R=Y=Me; Y=Cl, R-CH 2 CMe, CH 2 Ph, Ph), are prepared either by direct alkylation, or from the corresponding chloro-alkyls Cp*Cl n R 3-n . Cp*HfMe 2 (P t Bu 2 ) reacts slowly with H 2 to form a highly insoluble methyl hydridophosphide dimer, [Cp*HfMe(µ-H)(µ-P t Bu 2 )] 2 . The crystal structure of [Cp*HfMe(µ-H)(µ-P t Bu 2 )] 2 reveals a symmetric-bridged Hf 2 P 2 core with Hf-P distances of 2.805, 2.807 A. The hydride ligands have been tentatively located and form an assymetric Hf 2 H 2 bridge (Hf-H = 2.12, 2.33 A) orthogonal to the planar Hf 2 P 2 moiety. The final R index is 0.066. Hydrogenolysis of alkyl derivatives Cp*HfClR(P t Bu 2 ) (R = CH 2 CMe 3 , CH 2 Ph) affords an analogous chlorothydridophosphide dimer, [Cp*HfCl(µ-H)(µ-P t Bu 2 )] 2 . Treatment of Cp*HfCl(P t Bu 2 ) 2 with H 2 leads to rapid cleavage of Hf-P bonds and formation of [Cp*HfCl(µ-H)(µ-P t Bu 2 ] 2 . Cp*HfCl 2 (P t Bu 2 ) also reacts with H 2 , albeit slower, to give products derived from initially-formed Cp*HfCl 2 H. The relatively low Hf-P bond energy suggested by hydrogenolysis reactions in these systems is further indicated by the reaction of Cp*HfCl 2 (P t Bu 2 ) with CO to form the CO-insertion product, Cp*HfCl 2 (η 2 -C(O)P t Bu 2 ). The crystal structure of Cp*HfCl 2 (η 2 -C(O)P t Bu 2 ) exhibits dihapto carboxyphosphide functionality, with Hf-C = 2.203 and Hf-O = 2.117 A. The P-C(acyl) bond is 0.08 A shorter than P-C(alkyl) values, and suggests a significant P-π interaction. This has been confirmed by variable temperature studies, which reveal a substantial (10.7 kcal/mol) barrier to rotation about the P-C(acyl) bond. 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): Collins, Terrence J. Thesis Committee: Bercaw, John E. (chair) Chan, Sunney I. Grubbs, Robert H. Collins, Terrence J. Defense Date: 30 January 1984 Record Number: CaltechTHESIS:10222018-111603289 Persistent URL: https://resolver.caltech.edu/CaltechTHESIS:10222018-111603289 DOI: 10.7907/wbgr-yd42 ORCID: Author ORCID Roddick, Dean Michael 0000-0002-5981-4178 Default Usage Policy: No commercial reproduction, distribution, display or performance rights in this work are provided. ID Code: 11240 Collection: CaltechTHESIS Deposited By: INVALID USER Deposited On: 22 Oct 2018 22:32 Last Modified: 04 Nov 2025 21:55 Thesis Files Preview PDF - Final Version See Usage Policy. 47MB Repository Staff Only: item control page

SYNTHESIS, STRUCTURE, AND REACTIVITY OF HYDRIDE AND PHOSPHIDE COMPLEXES OF HAFNIUM AND ZIRCONIUM Thesis by Dean Michael Roddick In Partial Fulfillment of the requirements for the Degree of Doctor of Philosophy California Institute of Technology Pasadena, California 1984 (Submitted January 30, 1984) ii Acknowledgements I would like to thank a number of people, past and present, for their friendship and help during my stay at Caltech: from Mike Fryzuk, who introduced me to high-vacuum line techniques, to the present Bercaw crew (Alan, Tippy and his gismos, the 3 R's et al., etc.) who provided an intellectually(?) stimulating environment for me in the latter part of my graduate career. I would also like to thank Don for the moussaka, and Eric for his unflagging support of the California Golden Bears. In addition to members of the Bercaw group, there are several members of the Caltech community whose friendship and support deserve mention: George Spies, for his kindness and numerous jump starts, Dan Straus, for his com- panionship and advice, and Jeff Peake, for lasting more than 6 months as a roommate. Special thanks also to Bernie Santarsiero for all of his help, time, and patience, both in crystallographic work and in extracurricular activities. I am particularly grateful for the financial support and occasional good advice of John Bercaw, both prior to and during my graduate career, without which thesis -writing itself would be impossible. Finally, I would like to thank Nancy, who both professionally and personally has had a profound impact on my life. iii Abstract A series of alkyl hydride complexes C9 * Hf(H)R (R= Et, 2 CH CHMe 2 , CH cH 2 Ph; Cp * = n-C Me ) have been prepared by 2 5 5 2 reaction of cp 2* HfH with the appropriate olefin. The reac2 tions of these compounds with H and c H follow those of 2 2 4 the previously reported zirconium isobutyl hydride, cp * zr2 r-(H)CH2CHMe2' giving cp 2* HfH 2 · and metallacyclopentane Cp * Hf2 CH2cH2cH2cH2, respectively, plus one equivalent alkane. All alkyl hydrides examined exhibit high thermal stability and decompose only slowly at 80°C. The thermolysis of cp * Hf(H)CH CHMe yields a 1:1 mixture of cp * HfH and a 2 2 2 2 2 metallacyclobutane complex cp * HfCH CH(Me)CH . A proposed 2 2 2 mechanism for the formation of Cp * HfCH CH(Me)CH is given, 2 2 2 involving initial y-H abstraction from the isobutyl methyls of cp *Hf(H)CH CHMe • cp * HfH also reacts cleanly with ~-but2 2 2 2 2 ylacetylene to form a remarkably stable alkenyl hydride cornplex, Cp * Hf(H)CH=CH t Bu. The reactivity of Cp * Hf(H)CH=CH t Bu 2 2 with H and c H is similar to that observed for the related 2 2 4 alkyl hydrides. The hydride complexes cp * Hf(H)Ph and Cp * Hf2 2 (H)CH CMe have been conveniently prepared by the metathesis 3 2 of Cp * HfH with PhLi and LiCH CMe , respectively. 2 2 2 3 Cp *HfH reacts cleanly with allene to form the n-allyl 2 2 * hydride Cp Hf(H) (n 3 -cH CHCH ). 1 Hand 13 C NMR data as well as 2 2 2 3 labeling studies indicate that Cp;Hf(H) (n -cH CHCH 2 ) is high2 ly fluxional, and isostructural to cp * Zr(H) (n 3 -cH CHCH ). The 2 2 2 crystal structure of cp * Hf(H) (n 3 -cH CHCH ) is presented. The 2 2 2 iv coordination of the allyl ligand is confirmed to be trihapto, with notably asymmetric Hf-C(allyl) distances (2.38, 2.48, 2.57 A). The final R index is 0.049. The hydride ligand has been reliably located, and represents the first structurally characterized example of a terminal Hf-H bond. Cp 2* Zr(H)CH CHMe has been shown to react cleanly 2 2 with CO to form the enolate hydride Cp * Zr(H)OCH=CHCHMe . 2 2 A proposed mechanism for formation of Cp * 2 zr(H)OCH=CHC~e 2 involves hydride migration via the initially formed acyl 2 hydride Cp;zr(H) (n -C(O)CH CHMe ) to give a 2 2 ~-coordinated aldehyde complex cp * Zr(n 2 -OCHCH CHMe ), which subsequently 2 2 2 8-H eliminates to give the observed product. Support for the intermediacy of a ~-aldehyde complex in this transfer- mation is provided by the reaction of cp *M(H)CH CHMe 2 2 2 (M= Zr, Hf) with excess CO under controlled conditions to give moderately stable ~-aldehyde carbonyl complexes Cp *M(CO) (n 2 -OCHCH CHMe ). Thermolysis of Cp * Hf(CO) (n 2 -OCH2 2 2 2 CH2CID1e2) results in a novel coupling reaction to form the enediolate cp * HfOC(CH CHMe )CHO. The coordinatively unsat2 2 2 2 urated zirconium ~-aldehyde intermediate cp;zr(n -0HCCH 2 CHMe2) is also implicated in the reactions of acyl hydride cp * Zr(H) (n 2 -C(O)CH CHMe ) with trapping substrates c H , 2 4 2 2 2 Mec=cMe, H , and Hc=ctBu upon warming to give cp;zr(OCH(2 CH CHMe )cH cH ), Cp * Zr(OCH(CH CHMe )C(Me)=C(Me)), Cp 2* zr2 2 2 2 2 2 2 (H)OCH cH CHMe , and Cp * Zr(c=c t Bu)OCH cH CHMe 2 , respec2 2 2 2 2 2 tively. Carbonylation of the alkenyl hydride cp *Hf(H)CH=C2 HtBu did not yield an aldehyde complex, but rath~r _ the v metallacycle Cp;Hf(OHC=CHCH(tBu)). Mechanistic interpretations of these and related reactions are presented. A series of mono-ring, terminal phosphide complexes of hafnium have been prepared. Reaction of Cp * HfC1 one equivalent or excess LiPtBu 2 with 3 yields deeply-colored 2 2, phosphide complexes Cp*HfC1 (PtBu ) and Cp*HfCl(P~Bu } 2 2 respectively. Alkyl and aryl derivatives of Cp*HfC1 (PtBu ), 2 2 t Cp*HfR(Y) (P Bu ) 2 (R=Y=Me; Y=Cl, R-CH CMe, CH Ph, Ph), are 2 2 prepared either by direct alkylation, or from the corresponding chloro-alkyls Cp*ClnR _n· 3 Cp*HfMe (PtBu ) reacts 2 2 slowly with H to form a highly insoluble methyl hydride2 phosphide dimer, [Cp*HfMe(~-H) (~-PtBu 2 )] 2 . The crystal structure of [Cp*HfMe(~-H) (~-PtBu )] 2 2 reveals a symmetric- bridged Hf P core with Hf-P distances of 2.805, 2.807 A. 2 2 The hydride ligands have been tentatively located and form an assyrnetric Hf H bridge (Hf-H= 2.12, 2.33 A) 2 2 orthogonal to the planar Hf P moiety. The final R index 2 2 is 0.066. Hydrogenolysis of alkyl derivatives Cp*HfClR(P t Bu ) 2 (R= CH CMe , CH Ph) affords an analogous chloro2 2 3 hydridophosphide dimer, [Cp*HfCl(~-H) (~-P t Bu 2 )] 2 . Treat- ment of Cp*HfCl(PtBu ) with H leads to rapid cleavage 2 2 2 of Hf-P bonds and formation of [Cp*HfCl(~-H) (~-PtBu J 2 2. Cp*HfC1 (PtBu ) also reacts with H , albeit slower, to 2 2 2 give products derived from initially-formed Cp*HfC1 2 H. The relatively low Hf-P bond energy suggested by hydrogenolysis reactions in these systems is further indicated by the reaction of Cp*HfC1 (PtBu 2 ) with CO to 2 vi . 2 t form the CO-insertion product, Cp*HfC1 (n -C(O)P Bu ). 2 2 2 The crystal structure of Cp*HfC1 (n -c{O)PtBu ) exhibits 2 2 dihapto carboxyphosphide functionality, with Hf-C = 2.203 and Hf-0 = 2.117 A. The P-c(acyl) bond is 0.08 A shorter than P-c(alkyl) values, and suggests a significant P-~ interaction. This has been confirmed by variable temperature studies, which reveal a substantial (10.7 kcal/rnol) barrier to rotation about the P-c(acyl) bond. vii Table of Contents Chapter I. Synthesis and Reactivity of Alkyl, 1 Alkenyl, and Aryl Derivatives of Permethylhafnocene Dihydride Chapter II. Synthesis and Structural Characterization 26 3 of Cp;Hf(H) (n -cH CHCH ) 2 2 Chapter III. Reactions of Permethylhafnocene and 54 Permethylzirconocene Hydrides with co. Synthesis and Reactivity Patterns of Early Transition Metal Aldehyde Complexes Chapter IV. Synthesis and Reactivity of MonoPermethylcyclopentadienyl Hafnium Phosphide Complexes. Structural Characterization of [Cp*HfMe(~-H) (~-PtBu )J Cp*HfC1 2 2 t 2 2 and (n -C(O)P Bu ) 2 97 1 Chapter I Synthesis and Reactivity of Alkyl, Alkenyl, and Aryl Derivatives of Permethylhafnocene Dihydride. 2 Introduction Transition metal complexes bearing cis hydride and alkyl ligands comprise an important class of organometallic compounds. Typically, complexes is quite low, study the of reactivity the thermal and as a of such consequence systematic associated complexes has been limited.! ·stability with alkyl hydride McAlister, Erwin, and Bercaw have reported the facile insertion of isobutylene into the * zra 2 to form the isobutyl hydride complex Zr-H bonds of Cp 2 cp;zr(H)CH 2 CHMe 2 <1>. 2 In contrast to the majority of reported alkyl hydride complexes, the thermal stability of 1 is except ion a 11 y ° = 2 • 7 ·h) ( t ~ ( 7 4 C) hi gh and has permitted detailed study of its reaction chemistry. 2 ,3 The unusual stability opportunity to chemistry related of examine third row analog to in hydride Cp2ZrH 2, of 1 some suggested detail complexes Cp2HfH 2 to the derived <2>. 4 us the reaction from the Accordingly, we have prepared a series of hafnium (IV) alkyl, alkenyl, and aryl hydride complexes, the synthesis and reactivity of which is reported herein. Results and Discussion <1> Synthesis and Reactivity of Hafnium Alkyl Hydrides Solutions ethylene, of styrene Cp2HfH 2 or <2> isobutylene react to smoothly afford the with corres- 3 pending alkyl hydride complexes quantitatively shown in equation 1. c 1 H NMR), as This formal insertion reaction of an (1 ) 3, R = R' =H 4, R = R' = Me 5, R = H; R' = Ph olefin into a Hf-H bond is facile for ethylene and styrene, proceeding to completion in minutes at 25°C. the reaction of 2 with isobutylene conditions (80°C, hours) insertion; this is requires more and excess olefin perhaps due In contrast, to forcing to effect increased the steric interactions between the disubstituted olefin and the c Me 5 5 1 H NMR data (Table I) are in rings of 2. Infrared and accord with the formulation of 3, 4 and 5 as alkyl hydride complexes. Reaction of 3, 4, and 5 with excess ethylene induces reductive elimination of alkane with formation of the (6) metallacycle complex (equation 2). ,Cp~Hf:) 3' 4' 5 6 ( 2) Additionally, these alkyl hydride complexes are subject to hydrogenolysis under mild (1 atm H2 , 20°c, <1 h) conditions 4 to afford the parent dihydride, alkane (equation 3). 2, and the corresponding Reactions 2 and 3 have been examined cp;Hf(H)CH CHRR' 2 (3) 3, 4, 5 in detail for the related mechanistic aspects of these reactions have been previously discussed. 3 Complexes stability, 80°C. 3, 4, and 5 exhibit remarkable thermal undergoing little decomposition after hours at This stability is exceptional when compared to most cis alkyl hydride complexes, and is somewhat greater than that observed for analogous zirconium alkyl hydride 1, as might be expected. 5 Prolonged thermolysis of cp;Hf(H)CH 2 CH3 in benzene solution at 80°C cleanly yields (lH NMR) a 2:1 mixture of dihydride 2 and metallacyclopentane 6 plus one equivalent ethane (equation 4) • !::. Cp *HfH + 2 2 CP2Hf::) 7 6 3Cp *Hf(H)CH cH 2 3 2 3 ~ Observation of 6 + . C2H6 (4) implies the intermediacy of c H in thermolysis of 3: loss 2 4 of ethylene from 3 to form dihydride 2 followed by ethylene-promoted reductive elimination of alkane from 3 as 5 in equation 2 is consistent with the observed product distribution in reaction 4 (Scheme I). 3 6 The thermolysis of Cp*Zr(H)CH CHMe 2 2 (1) 2 Scheme I to yield isobutane plus products derived is reported from thermal cc 5 ccH > ><c ccH > cH >5 3 4 2 3 5 thermolysis of benzene or toluene decomposition of initially formed ZrH.6 In solutions contrast, of isobutyl hydride 4 at 110°C yields a 1:1 mixture of dihydr ide 2 and metallacyclobutane CpzHfCH CH2 (CH3>cH2 (7) plus one equivalent isobutane (equation 5). When the thermolysis is carried out in the 4 2 7 ( 5) 6 presence produced pure, of < excess isobutylene, 7 is quantitatively 1 H NMR), and may be isolated as an analytically off-white crystalline solid in 62% yield. The formulation of 7 is confirmed by solution molecular weight cc 6 o6 , calc.: 505, found: 486), and by 1 H and 13 c NMR data, which compare closely to data for analogous, titanacyclo- butane complexes. 7 A reaction similar to 5 has recently been reported (R = CH CMe 3 , 2 2 Labeling studies have shown this for the related bis-alkyl actinides Cp2ThR CH SiMe > (equation 6>. 3 2 8 * ~ Cp Th~XMe 2 + XMe 4 y-hydrogen abstraction~ 9 2 ( 6) X = C 1 Si reaction to proceed via By analogy, a mechanism to account for the formation of 7 in reaction 5 is given in Scheme II. tion of 7 could proceed via the 10 intermediacy of the obtained tionation of 4. Alternatively, forma- from the bis- dispropor- However, at 80°C, a temperature where 4 is the sole observable reactant species in solution, the rat2 of thermolysis of 4 is essentially olefin independent, and C * /CH2CHMa. P2Hf -z "-H 4 - ~ /CH 2CHMe cp;l;ft--~---- JH2 I I I I _, I 1 I I H------H + H2 - CH 2CHMe 3 -H2 -.....J ~pMe Cp;Ht~+H Cp;HtH 2 2 ,......, 7 ~ Scheme II 8 would thus appear to rule out Y-hydrogen abstraction from Cp2Hf(CH 2 CHMe 3 >2 as a significant route to 7. The reversibility of y-hydrogen abstraction shown in Scheme II is confirmed by the facile reaction of 7 with a at 25°C to 2 form dihydride 2 plus isobutane (equation 7). (7) 2 7 The thermal stability of 7 is substantially greater than that reported for normal ring group IV metallacyclobutane Cp 2 McH cccH > cH (t~(25°C> for M=Ti: 2 3 2 2 3 h; Hf: 9 d>, 11 with negligible decomposition complexes 1-2 h; zr: c1 H NMR) after days at 115°C. 7 thermolyzed similarly worthy, in the presence of unchanged. in observed for Significantly, solutions of light This of the lack excess ethylene remain of reactivity is extensive metathesis activity ti tanacyclobutanes, 7 and appears note- to reflect the inaccessibility of the methylidene propene complex 8 in reactions of 7. MYMe 7 8 9 (2) Synthesis and Reactivity of Cp2Hf(H)CH=CHtBu A reaction related to the regioselective insertions of unactivated olefins into Hf-H bonds discussed in the previous section in the corresponding insertion involving unactivated acetylenes. Toluene solutions of 2 react rapidly with one equivalent of 1-butylacetylene at ambient temperature to yield Cp2Hf(H)CH=CHtBu (9) (equation 8), (8) + 2 9 isolable as (v(Hf-H = 1560 em -1 a colorless, crystalline 1625 cm- 1 ; = 1 > and H NMR V(Hf-D) solid. 1155 3 ( JHH = 21 Hz, Infrared cm-l Cli=C~CMe v(C=C> = 3 > spectro- scopic data support the formulation of 9 as a trans alkenyl hydride complex. Attempts to prepare other alkenyl hydride complexes less HC=CMe using or HC=CPh products. 12 The thermally benzene terminal acetylenes resulted instead in doubly-inserted 9 is somewhat more hydrides 3, 4 and with of N2 125°C. alkenyl stable than solutions of noticeable somewhat bulky hydride alkyl 9 under 1 decomposition after days at while much attention surprising that atrn such 5, as showing no It is has ~ ~ en focused on the role of alkyl hydride complexes in clef .in 10 hydrogenations, there have been relatively few studies of the corresponding acetylene systems. Moreover, although several reports have appeared concerning reactions of metal dihydrides with acetylenes, 13 reaction 8 represents to our knowledge the first unambiguous example of a metal hydride addition to an unactivated acetylenic bond to form a stable cis-alkenyl hydride complex. Solutions of 9 react cleanly with ethylene to yield Cp*Hf ( Et > ( CH=CH tBu > < 10 > as a colorless oil, as shown in Solution infrared and 1 H NMR identify 10 as equation 9. ( 9) the product of ethylene insertion into the Hf-H bond of 9. Reaction 9 contrasts with that of Cp* Zr(H)CH CHMe <1> and 2 2 2 ethylene, where ethylene insertion into the Zr-H bond has been shown to toward 1 and be reversible c2 a4 • 3 with the equilibrium lying Thermolysis of 10 in the presence of excess ethylene results in quantitative ge?eration of 6 and neohexane (80°C, 6 h), according to equation 10. Analogously to reaction 3, 9 reacts with H in stepwise 2 11 10 fashion 14 6 to yield the dihydride 2 (10) and neohexane (80% conversion after 72 hat 25°C, 3 atm H > (equation 11}. 2 (11) 2 9 (3} (2} with RLi (R = Ph, CH CMe l 2 2 3 The synthetic procedures described in the preceding Reaction of Cp2HfH sections <equations formation 1 and 8 > are hydrocarbon of necessarily products with limited to S-hydrogen functionality, and are thus inappropriate for the synthesis of phenyl and neopentyl derivatives of 2. Consideration of the pronounced hydricity of Zr-H and Hf-H bonds 15 suggested a degree of hydride uninegative, ligands metathesis of of 2. halogen-like Thus, transition metal by character analogy halides to the the ready with alkyl1 i thium it was hoped that Cp * HfH would exhibit 2 2 Indeed, treatment of metathetical reactivity. reagents, for ~ im~lar ~oLuene 12 solutions of 2 with one equivalent PhLi provides a novel route to the phenyl hydride Cp2Hf(H)Ph equation 12. <11> as shown in The thermal stability of 11 is comparable to (12) that of alkenyl hydride 9, after days at 125°C. with no decomposition evident Similarly, reaction of 2 with one equivalent LiCH 2 CMe yields Cp2Hf(H)CH CMe (12>, together 3 2 3 with -10% of two uncharacterized sideproducts (equation 13). Reactions 12 and 13 demonstrate the marked (13) hydridic character of group IV metal hydrides relative to metal hydrides to the right in the periodic table, which typically deprotonate in the presence of strong bases. example, cp MH (M 2 2 lithiated tion 14>. 16 = Mo, W) For reacts with n-BnLi to give a tetramer, [Cp M<H>Li] plus butane 2 4 It should be noted, however, that the (equa- (14) M = Mo, W coordinative unsaturation of Cp2HfH provides for a direct 2 metal-alkyl anion interaction using the vacant equatorial 13 la 1 LUMo. 17 This interaction is not available for the 18 electron Cp wH , 2 and may be 2 responsible in part for the contrasting reactivities observed. Conclusion A series of bis-(pentamethylcyclopentadienyl)-hafnium (IV) hydride complexes have been prepared, encompassing a range of hydrocarbon ligand types: S-hydrogens), alkenyl, and alkyl aryl. olefinic and acetylenic bonds (w~th Facile and without insertion of into Hf-H bonds provides a general route to a variety of alkylhydride derivatives of 2. Additionally, metathesis with hydride alkyl and ligands of 2 aryllithium undergo reagents ready to give derivatives of 2 not obtainable via simple insertion. While the reactions reported in this chapter· in many ways parallel those of significant differences the related system, some in reactivity are evidenced. In particular, thermolysis of alkyl ( 4) affords a product derived elimination of alkane, as Cp2Zr hydride Cp2Hf(H)CH CHMe 2 not observed from for formal 2 reductive Cp2Zr(H)CH CHMe 2 2 (1), but rather from an alternate pathway y-abstraction to form metallacycle metal center. An 7 by which important 4 avoids factor to reduction be of the considered in comparing the reactivities of zirconium and hafnium systems is the relative energetics of the M(IV) ~ M(II) couple. 14 Reactions involving the Zr(IV) ~ Zr(!I) are anticipated to be much more energetically accessible than analogous reactions involving hafnium; thus, mechanisms which circumvent such couples are undoubtedly preferred for hafnium. TABLE I. NMR~ AND IR~ DATA Compound Cp *Hf(H)CH 2 CH 3 (3) 2 Assignment IR V(Hf-H) 1630 C5(C!!_3)5 Nucleus Chemical Shift lH 1.90 s C!!_ CH 3 2 CH C!!_ 2 3 HfH • Cp Hf(H)CH CHMe 2 (4) 2 2 v(Hf-H) 1636 C5(C!!_3)5 \1 (Hf-H) 1620 C5(C!!_3)5 lH C5(C!!_3)5 C!!_ cu cu 2c!!_ 2 2 2 cu cu cu 2cH 2 2 2 3J = 8 0.68 t 3J = 8 1.96 8 -0.21 d 3J = 6 1.02 d 3J = 6 13.64 s,br lH l. 93 8 0.30 m C!!_ CH Ph 2 2 CH C!!_ Ph 2 2 CH CH Ph 2 2 HfH * -(CH --Cp2Hf 2 cu 2cu 2cH 2 ) (6) 0.03 q 12.41 8,br C!!_ CHMe 2 2 CH CHMe 2 2 HfH Cp *Hf(H)CH cH Ph (5) 2 2 2 Coupling Not observed 7. 30 m 13.71 s,br lH l. 84 s 0.44 m 2.10 m 1--' Ul TABLE I (cont'd) Compound Assignment IR c cp * HfCH CH(CH )cH 2 (7)3 2 2 C5(C!!_3)5 Nucleus Chemical Shift lH 1.72, 1.87 s CH CH(C!!_ )cH 2 2 3 C!!_ CH(CH )C!!_ 3 2 2 l. 54 d 0.79 dd l. 27 dd £s(CH3)5 Coupling 13c 7.45 q CH 2 CH (£H)) CH 2 23.57 d CH £H(CH )CH 2 3 2 68.21 t £H 2CH (CH ) £H 2 3 J 1 3J ::; 12 2 J=l2, 3J=9.5 114.74, 115.46 10.89, 11.80q cs (£HJ) s 2 1 1 1 1 J = 126 J = 129 J = 120 J = 127 1--' 0'\ Cp;Hf(H)CH=CHtBu (9) v(Hf-H) 1625 C5(C!!_3)5 v (Hf-D) 1155 C!!_=CHtBu v(C=C) Cp~Hf(Et)CH=CHtBu (10) v(C=C) 1560 1558~ 1H 1.91 s 5.80 d CH=CHtBu 4.81 d CH=CHtBu 1.09 s HfH 12.83 s,br C5(C!!_3)5 1H 3 J = 21 J = 21 1.78 s C!!_=CHtBu 5.23 d CH=CHtBu 4.87 d CH=CHtBu 1.07 s C!!_ 2cu 3 -0.08 q CH C!!_ 2 3 3 l. 29 t 3J = 19 3 J = 19 3 J = 7.5 3J = 7. 5 TABLE I (cont'd) Cp;Hf(H)Ph (11) Cp * Hf(H)CH CMe (12) 2 3 2 Assignment IR Compound v (Hf-H) 1630 v(Hf-H) 1630 C5(C!!_3)5 Nucleus Chemical Shift lH l. 78 s Ph 6.67, 6.98 m HfH 13.14 s,br lH C5(C!!_3)5 1.96 Coupling 8 C!!_ CMe 2 3 -0.16 s CH CMe 3 2 1.20 8 HfH 14.04 8 ~ 1 H (90 MHz) and 13 c (22.5 MHz) NMR spectra taken in benzene-d6 at ambient temperature. in 6 relative to internal TMS or residual protons or carbons-in solvent. b IR spectra obtained as Nujol mulls except where indicated. in the Experimental Section. ~ 1 H NMR spectrum obtained at 500 MHz. d IR spectrum obtained for neat oil. e . - IR spectrum obta~ned for . c 6 o6 solut~on. Chemical shifts are reported Coupling constants are reported in Hz. Values are given in Hz. The complete spectra are detailed ......... ~ 18 Experimental Section General Considerations. All manipulations were carried out by using either high vacuum line or glovebox techniques. first from Solvents LiAlH 4 were or purified benzophenone by vacuum ketyl and then "titanocene", prepared as described earlier . 18 was by over on purified passage MnO 0 activated 4-A molecular sieves. transfer from Hydrogen vermiculite 19 and Ethylene and isobutylene (Matheson) were used directly from the cylinder. All other reagents molecular sieves were or determined degassed and transferred received. Elemental used as by Alfred Bernhardt, D nis from analyses and were Kolbe, and C.I.T. Analytical Laboratories. 1 H NMR spectra were recorded with Varian EM-390, JEOL FX90Q, or Bruker 500 MHz spectrometers. were JEOL recorded with a spectra Nujol em FX9 OQ were measured on a nulls unless spectrometer. Beckman otherwise 13 C NMR spectra noted Infrared 4240 spectrometer as and are reported in -1 Many reactions were carried out in sealed NMR tubes and moni tared by NMR spectroscopy. ( 0. 0 6 mmol) of 4 was 14/20 ground glass adapter. Benzene-g placed in A typical example is 30 mg an NMR tube joint and fitted with a 6 sealed to a teflon needle was vacuum transferred into the tube 19 at -78°C, 1 atm H2 admitted, the tube cooled to -196°C and then sealed with a torch. Procedures. A solution (1.25 mmol) Cp2HfH room temperature 2 of under 200 torr trated and cooled to -78°C. 919, 802, (61%) ethylene for 1 of 3. IR: 1630 ( br), concen- 1488, C, Found: hour. Filtration and drying in vacuo 778. 7.57; Hf, 37.26. g in 15 ml petroleum ether was stirred at Excess ethylene was removed and the solution was yielded 0.39 g 0. 60 1022, 55.15; H, C, 55.03; H, 7.42; Hf, 37.10. fE~Hf(H)CH CHMe 2 2 (4). A thick-walled glass reaction vessel with teflon needle valve was mmol > Cp*H£H , 2 5 ml toluene, for 2 days. a stirred at 80°C charged with and 8 rnmol 1. 0 g ( 2. 0 isobutylene and Volatiles were removed in vacuo; workup with petroleum ether afforded 0.795 g (71%) of white crystalline 4. IR: 1636 ( br), 1302, 1155, 1028, 805 , 770 . Ana 1 . Ca 1 c d • for C C , 5 6 . 8 5 ; H, 7 . 9 5 ; H OHf : 24 4 C, 56.68; H, 8.12; Hf, 34.94. Hf, 35.20. Found: To (0.91 mmol) Cp*H£H lil < 0. 9 6 flow. mmol) 2 a stirred solution of 0. 41 g in 15 ml toluene at -78°C was added 110 styrene via syringe under argon co\,ln ter- The solution was warmed to room temperature, stirred an additional 30 minutes, and worked up with petroleum 20 ether to give 0.36 g (71%) of 1 H NMR). 3060, pure, IR: white 1620 crystalline 5 ( br), 1492, <>95% 1053, 1030, 975, 806, 776. ££2Hf(CH 2 cH 2 cH 2 cH 2 > (6). except Cp*HfH , 10 ml toluene, and 2 72.6 mmol c 2 H4 were stirred at 80°C for 24 hours. Workup with 1.0 g (2.22 The procedure for 4 was followed mmol) petroleum ether afforded metallacyclopentane 6. IR: 0. 80 g ( 61%) 1490, 1022, 993. C, 57. 0 8; H, 7. 58; Hf, 3 5. 3 4. of off-white Anal. Calcd. Found: c, 57.06; H, 7.59; Hf, 35.43. f2~Hf(CH 2 CH(CH 3 >cH 2 > (7). The procedure for 4 was followed except l.Olg(2.24 mmol) Cp*HfH , 10 ml toluene, and 9 mmol 2 isobutylene were stirred at 115°C for ten days. Petroleum ether workup yielded 0.685 g (62%) of off-white crystalline 7. 1 H NMR of the workup residue indicated >90% 7, with traces of 2 and 4. IR: 1490, 1298, 1053, 1023, 978, 938. Anal. Calcd. for c a Hf: 24 38 C, 57 .08; H, 7 .58. Found: C, 56.86; H, 7.51. To a solution of 1.0 g (2.22 mmol) Cp 2 HfH in 15 ml petroleum ether was condensed 2. 50 mmol 2 !-butylacetylene at -196°C. The reaction mixture was stirred for 30 minutes at -78°C and allowed to warm to room temperature. Concentration, cooling to -78°C, and 21 filtration afforded 0.56 g (47%) IR: of white crystalline 9. 1624 ( br), 1560, 1490, 1360, 1252, 1218, 1204, 1064, 1026, 1005, 805. Anal. Calcd. for c 26 H Hf: C, 58.58; H, 42 Found: C, 58.32; H, 7.89; Hf, 33.26. 7.94; H, 33.48. ( 10) . fE2Hf(Et)CH=CHtBu To a 0.66 of solution g (1.24 mmol) Cp2Hf(H)CH=CHtBu in 10 ml toluene was condensed 3.0 mmol ethylene at -196°C. The reaction mixture warmed to room temperature and stirred for 2 days. was Removal of the volatiles in vacuo left a colorless oil, identified by 1 H NMR as >95 mol % 10. IR: 1558' 1490' 1357' 1250' 1215, 1200, 1060, 1021, 1000, 801. <6 . 7 mmo 1 ) of in 60 ml petroleum ether at -78°C was syringed ££~ H f ( H ) Ph cp;HfH 2 3.3 ml ( 11 ) . (7.3 mmol) hexane/diethyl mixture was stirring. allowed concentrated, crystalline of ether After so 1 uti on of 3 . 0 2 g To a 18 2.2 M phenyllithium solution, Aldrich). to to warm hours, and cooled precipitate was 1487, 1414, 710. Anal. Calcd. Found: C, 58.93; H, 6.89. c H Hf: 26 36 reaction temperature IR: off was with filtered, C, and dried 3 0 4 5, 16 50 1238, 1059, 1050, 1023, for cycle- The resulting white filtered of 11. The solution to -78°C. vacuo, giving 1.82 g (52%) 1568, the room (70:30 804, 59.25; 785, H, in < br) , 726, 6.88. 22 £22Hf(H)CH 2 CMe 3 (12). Cp 2 HfH (0.50 g, 1.1 mmol) 2 (0.088 g, 1.1 mmol) were placed in a flask, LiCH CMe 3 2 10 ml of petroleum ether was distilled in at -78°C. and and The reaction mixture was warmed to room temperature and stirred for 12 hours. Concentration and cooling to -78°C afforded 0.24 g (42%) of 12, approximately 90% pure by 1 H NMR. 1635, 1485, 1400, 1354, 1204, 1083, 1022, 774, 693. IR: 23 References (1) Some notable exceptions are: (a) Norton, J. R. Ace. Chern. Res. 1979, 12, 139. (b) Halpern, J. Ibid. 1982, 15, 332. (c) Gell, K . .I.; Schwartz, J. J. Am. Chern. Soc. 1978, 100, 3246. (2) Manriquez, J. M.; McAlister, D. R.; Sanner, R. D.; Bercaw, J. E. (3) J. Am. Chern. Soc. 1978, 100, 2716. McAlister, D. R.; Erwin, D. K.; Bercaw, J. E. J. Am. Chern. Soc. 1978, 100, 5966. (4) Roddick, D. M.; Fryzuk, M.D.; Seidler, P. F.; Hillhouse, G. L.; Bercaw, J. E., manuscript in preparation. (5) Similar stability trends for zirconium and hafnium complexes have been noted: (a) Planalp, R. P.; Andersen, R. A.; Zalkin, A. Organornetallics 1983, ~' 16. Raston, (b) Cardin, D. J.; Lappert, M. F.; c. L.; Riley, P. I. "Comprehensive Organometallic Chemistry"; Wilkinson, G., ed.; Pergamon Press: New York, 1982, Vol. 3, 559-634. (6) Manriquez, J. M., Ph.D. Thesis, California Institute of Technology, 1976. (7) Howard, T. R.; Lee, J. B.; Grubbs, R. H. J. Am. Chern. Soc. 1980, 102, 6877. ( 8) Bruno, J. w. ; Marks , T. J. ; Day, V. W. 1982, 104, 7357. J. Am. Chern. Soc. 24 (9) Whereas labeling studies 8 appear to exclude a-abstraction or homolytic bond scission processes, it should be noted that ring methyl C-H abstraction ruled out. 3 has not been The detailed mechanism of reaction 6 is currently under investigation in our group: Bulls, A. R., work in progress. (10) The possible intermediacy of (C Me ) (C Me cH )HfH, 4 5 5 5 4 2 formed via initial reductive elimination of isobutane from 4, in reaction 5 has been addressed: thermolysis of (C Me ) (C Me cH )HfH in the presence of isobutylene 5 4 2 5 5 results solely in "tuck-in" products analogous to those reported for zirconium. (11) Seetz, J. w. F. L.; Bickelhaupt, F. 6 Schat, G.; Akkerman, 0. S.; Angew. Chern., Int. Ed. Engl. 1983, ~, 248. (12) (a) McGrady, N. D.; McDade, C.; Bercaw, J. E. "Organometallic Compounds", Shapiro, B. L., ed.; Texas A&M University Press: College Station, Texas, 1983; pp. 46-85. (.b) Roddick, D. M. , unpublished results. (13) J. Am. Chern. Soc. 1972, (a) Nakamura, A.; Otsuka, S. 94, 1886; ibid., 1973, 95, 7262. Bresadola, S. (b) Long a to, B.; Inorg. Chern. 1982, 21, 168. (_14) Nonitoring of reaction 11 by 1 H NMR indicated the presence of free neohexene during early stages of the hydrogenation. 25 (15) Bercaw, J. E. "Transition Metal Hydrides", Bau, R., ed.; Adv. Chern. Ser. 167; American Chemical Society: Washington, D.C., 1978, pp. 136-148. (16) Francis, B. R.; Green, M. Moser, G. A. (17} J. L. H.; Luong-thi, T.; c. S. Dalton, 1976, 1339. Lauher, J. W.; Hoffmann, R. ~, J. Am. Chern. Soc. 1976, 1729. (18} Marvich, R. H.; Brintzinger, H. H. 1971, J. Am. Chern. Soc. 2i' 2046. (19) Brown, T. L.; Dickerhoof, D. W.; Bafus Morgan, G. L. D. A.; Rev. Sci. Instrurn. 1962, 33, 491. 26 Chapter II Synthesis and Structural Characterization of Cp *Hf(H) (n 3 -CH CHCH ). 2 2 2 27 Introduction Transition metal complexes containing allylic ligands comprise an complexes. been important class In particular, implicated as key of reactive n-allyl hydride complexes have intermediates metal-assisted hydrocarbon rearrangements are of considerable organometallic interest. Some in 1 a number of and, therefore, time ago, the early 3 transition metal n-allyl hydride complexes Cp2Zr<H><n -cH 2 3 CHCH2> <1> and Cp2Zr<H><n -cH 2 CHCHMe) (2) were prepared in our laboratories (equations 1 and 2>. 2 ( 1) ( 2) The thermal stabilities of 1 and 2 are quite high, and have permitted the reaction chemistry and fluxional behavior of these complexes to be studied in detail. In this chapter we report the synthesis and structural characterization of the hafnium analogue to 1, 3 Cp2Hf (H) <n -cH CHCH ) 2 2 that allyl consequently, ( 3). Spectroscopic data and isostructural; hydrides 1 3 are the structural study x-ray of indicate 3 provides 28 useful information complexes, pertaining as well as to the bonding insight into the dynamic operative in these molecules. in these processes 29 Results and Discussion Treatment of petroleum ether solutions Cp~HfH of 2 with one equivalent of allene readily afforded analytically pure, white crystalline Cp2flf<H><n 3 -cH CHCH > 2 2 yield (62%) (equation 3). (3) in good Cp * Hf(H) (n 3 -CH CHCH ) 2 2 2 ( 3) 3 been characterized by its 1 H and 13 c 3 has NMR spectra, which compare closely to that of 1 (Table I). Although rr coordination of and clearly allyl established 1 igands by in infrared complexes 1 data, IR 2 spectra was of 3 display a number of bands in the diagnostic hydride/allyl region (see Experimental Section) and could not be reliably assigned. As was the case for zirconium allyls 1 and 2, 1 H and 13 c NMR data indicate the 3 is fluxional. Thus, ambient temperature 1 H NMR spectra exhibit a single resonance for both <n 5 -c Me > rings at 1.78 pm, and a quartet of doublets 5 5 3 at 3.48 ppm c JHH ave = 12.5, 2.1 Hz) for the central allyl proton. Although located, 13 c NMR reveals a 1 = 155.2 (triplet, allyl JHC carbons allyl CH 2 the terminal groups. protons were not single resonance at 57.17 ppm Hz) consistent allyl attributable with a rapid to the terminal equilibration of The small 2.1 Hz splitting observed for CH CHCH arises from coupling to the hydride ligand, which 2 2 30 appears as a broad singlet at 3.58 ppm. ( n5 -C 5 Me 5 > proton resonances of 3 zirconium allyls interchange and carbon can be 1 and and The equivalence of allyl rationalized 2, 2 b and syn-anti dynamic nature in terminal carbon analogously terms of a equilibration to n 3 -n 1 rapid as the shown in Scheme 1. The variable temperature 90 of MHz 3 has been confirmed by 1 H NMR. Upon cooling, the <n 5 -c 5 Me 5 > singlet for 3 broadens and coalesces at ~69°C. At -80°C, 1 H NMR of 3 displays a pair of singlets for the inequivalent = 11.0 <n 5 -c 5 Me 5 > groups at 1.72 and 1.83 ppm with 6v ± 0.5 Hz, consistent with a groundstate n3 -allyl From these values, ~G*C-69°C> structure (vide infra). for equilibration of permethylring groups of 3 is calculated 3 to be 10.5 ± somewhat 0.1 kcal mol- 1 • less than the Surprisingly, this value is corresponding barrier found for 4 0 In c = -a c) . light of the complexity of Scheme 1, it is not clear what zirconium analog 1 of 12.5 kcal mol-l <T factors are responsible for this equilibration process and the observed ordering of 1 and 3. At elevated (80°C) temperature the central proton of 1 appears as a sextet in the 1 H NMR, of an exchange process equilibrating allyl protons and the hydride ligand. the indicative four terminal This observation has been rationalized in terms of a rapid alkyl hydride propene contrast, complex 1 H NMR allyl equilibrirn, as shown in Scheme 2. spectra of 3 exhibit no changes In up to 31 Scheme I ) Zr la 'H Zr~ Ib Scheme 2 ' H 32 decomposition (125°C>. Although dynamic NMR behavior was not observed for 3, the tautomerism in Scheme 2 has been demonstrated on the chemical timescale for cp;Hf<H><n 3 -cH 2 CHCH2 > by the complete scrambling of deuterium in c~;Hf<D><n 3 -ca 2 coca 2 > (prepared by reaction of CpHfD 2 with allene at -30°C <1 H NMR)) into the terminal allyl positions after 15 minutes at room temperature (equation 4). D *7\ II~ Cp Hf 2 D cp;HfL] .J'' CH D [ D 2 D J * Cp Hf 2 7\-D etc. ( 4) ""'-H Crystallographic Results and Discussion The molecular structure of Cp2Hf<H><n 3 -cH caca > (3) 2 2 is presented in Figure 1, a stereo view in Figure 2, and a skeletal view of the immediate ligation about the hafnium with relevant bond distances and bond angles is given in Figure 3. The hafnium atom in 3 adopts the familiar pseudotetrahedral "bent sandwich" cp Mx 2 configuration, if 2 5 3 <n -c 5Me 5 > ligands and X = H <n -cH 2 CHCH 2 > are considered to occupy single coordination sites. The Hf-ring centroid 0 distances of 2. 243 and 2. 233 A and the ring centroid-Hfring centroid angle of 137.5° (Tables III and IV) are greater than typically found for unsubsti tuted bis ( cyclopentadienyl)hafnium complexes, but compare closely to 33 C (12M} Q C(l2)~ C(ll) C(liM} C(21M} Figure 1. Structure of Cp 2*Hf(H) (n 3 -CH 2 CHCH 2 ) (3). 34 Figure 2. Stereo view of Cp * Hf(H) (n 3 -cH CHCH ) 2 2 2 (3). 35 1.39(2) 2.48(2) C(2) 1.85(7) H Figure 3. Skeletal view of Cp * Hf(H) (n 3 -CH CHCH ) 2 2 2 (3), with selected bond distances (A) and angles ( 0 ) . 36 values for {Cp~ZrN permethylzirconocenes 0 2 2 2 } N (2.232 A; A; 138.9°>. 6 141.3°> 5 and Cp~Zr(C(O)CHPMe >H (2.251, 2.258 3 The inner-ring carbons of 3 are coplanar (Table v) , and the small variations observed for Hf-C(ring> distances 0 (2.448(7)-2.563(10) coordination. A) As are not observed unusual for pentahapto previously for other bent permethylmetallocene structures, the ring methyl groups are displaced out of the cyclopentadienyl ligand planes away from the metal center. correlate well with nonbonding distances methyl nonbonding C(llM)-C(21M) C(l)-C(l3M) The observed inter-ring <Table VI> , distances = 3.25(2) 0 A, and with c-c ring-allyl the C(l)-C(23M) C(2)-C(23M) displacements shortest = ring 0 3.21(2) 0 = 3.30(2) A, A, and 0 = 3.40(2) A involving methyl carbons having the greatest deviations from planarity. A further indication of steric crowding in 3 is the staggering of the (see Figures 1 and 2). <n 5 -C 5Me 5 > This serves to not only minimize inter-ring methyl contacts, but also successfully avoids severe steric interactions with the allyl ligand. The allyl bonding in 3 is somewhat unusual. Although the allyl moiety is clearly rr-bond, the Hf-allyl bonding is notably asymmetric, with 0 • the Hf-carbon (central) distance • (2.48(2) A) ~nterrned~ate between terminal distances Hf-C(l) 0 0 = 2.38(2) A and Hf-C(3) = 2.57(2) A. other reported transition metal allyl This contrasts with structures, where metal-carbon(central) distances are typically shorter than the respective metal-carbon(terminal) distances. Complex 3 37 also apparently exhibits an asymmetry in the C-C bonds of the allyl 0 1.33(2) A). group Taken variations suggest a 0 = (C(l)-C(2) 1.39(2) together, these degree of 11 A, with supra) complexes for the observed 1, 2 and = observed bond length 1 -<cr )allyl character for Cp2Hf<H><n 3-cH 2 CHCH 2 > (canonical form lb>. 7 consistent C(2)-C(3) dynamic 3, This result is equilibria presumed intermediates such as Ia and lb (Scheme 1). to (vide involve The apparent preference for canonical form lb over Ia is reminiscent of group IV n 2 -acyl metallocene structures, where interaction of an acyl oxygen lone pair with the empty, central equatorial low-lying orbital of the bent sandwich moiety CIIa> favored is the thermodynamically isomer. 8 Alternatively, a steric interaction between the C(3) allyl II a IIb 38 carbon and the hydride ligand (H-C(3) = 2.48(7) number of 0 may A) contribute to the observed asymmetry. The allyl) bonding geometries complexes have for been a compared using parameters described by Ibers 9 (Figure 4}. the distance from Hf (A}, for 3 (2.25 a set of The value of D, to the centroid of v metal- ( n 3 - the allyl group 0 A} differs by 0.11 A from that in cp 2 Ti<n 3-ca 2 cacH > (2.14 A>, 10 and is in accord with the 2 u 0 difference in metal radii (Hf: 1.44 A, Ti: 1.32 A; !:::. = The tilt angle defined T, subtended by the Hf-A and C(2}-A vectors, as the angle is 117°, within the range observed for other n-allyl structures (100-125°). value of S , the angle C ( 1} -c ( 3) vectors in 3, 9 6°C, The between is the Hf-A somewhat larger and the B than ~ngles of 90-93° found in other n-allyl complexes, however, and reflects the allyl bonding asymmetry previously noted. The hydride ligand first in 3 is structurally of interest, characterized as it represents the terminal Hf-H bond. The observed bondlength, 1.85(7) A, is somewhat (J shorter <2.06<2> than bridging Hf-H values for <n 5 -c 5 H 4 cH 3 > 2 H£<BH 4 > 2 and Cp*HfMe(~-H)(~-PtBu > A> , 12 Hf(BH 4 > 4 <2.069<7>, A>, 13 2 2 (2.12(13), 2.33(13} A>, 14 and compares closely to terminal Zr-H values 2.120(8) for Cp2Zr(H)CH 2 P(CH 3 > 2ca 2 (1.88(4} 15 PMe3~H (1.89(2) A}. ~> 15 and Cp!Zr(C(Q}CH- NMR~ DATA TABLE I. Compound; Solvent and Temperature • 3 Cp Zr(H) (n -CH CHCH ) 2 2 2 Toluene-~ , +25° 8 Toluene-~ 8 , -55° Assignment Nucleus Chemical Shift C5(C~3)5 lH 1. 72 s CH 2 C!.!_CH 8 , +65 ave = 12 C!.!_ CHC!.!_ 2 2 ZrH not observed C5(C!.!_3)5 1.64' 1. 75 CH C!.!_CH 2 2 3.47 m C!.!_ 2 CHC!.!_ 2 1.06 d J = 13.7 C!.!_ CHC!.!_ 2 2 1.36 d J = 17.1 C!:!_ 2 CHC!.!_ 2.15 d J = 8.5 J = 10.1 3.88 s, br 2 C!.!_ CHC!.!_ 2 2 ZrH Toluene-~ 3J 3.47 quint 2 Coupling ~5(CH3)5 C5(~H3)5 ~H CH 5 not observed 3.91 d l3C{lH} 111.3 12.4 2 CH~H 2 58.1 2 ~HCH 2 116.5 w \0 TABLE I (cont'd) Compound; Solvent and Temperature Cp *Hf(H) (n 3-CH CHCH ) 2 2 2 Benzene-~, +34° Toluene-~ 8 , -80° Benzene-~, +25° (l) Assignment Nucleus Chemical Shift C5(C!!3)5 lH 1. 78 8 CH 2 C!!CH 2 3.48 quint of d C!!2 CHC!! 2 not observed HfH 3.58 s, br c5 (C!i3) 5 1.72, 1.81 s, br CH 2C!!CH 2 not observed C!! 2CHCH 2 not observed HfH 3.41 s, br f5(CH3)5 llc Coupling Jave = 12.5, 2.1 ~ 0 109.9 s 11.7 q 1J £H 2CH£H 2 57.2 t 1J CH 2 £HCH 2 114.4 d 1 J :: 139 C5(£H3)5 = 126 = 155 ~ 1H (90 MHz) and 13 c (22.5 MHz) chemical shifts are reported in 6 relative to internal THS or residual protons or carbons in solvent. Coupling constants are reported in Hz. 41 Experimental Section General Considerations. performed using either glove All box techniques as described previously. manipulations or 16 high vacuum line Cp~HfH 2 and cp;Hfo 2 were prepared using established procedures . 17 used directly from the cylinder. were Allene was Elemental analysis of 3 was determined by Alfred Bernhardt Analytical Laboratories. 1 H NMR spectra were recorded using Varian EM-390 and Bruker 500 MHz spectrometers. 13 c NMR obtained using a JEOL FW90Q spectrometer. spectra were Infrared spectra were measured on a Beckman 4240 spectrometer as nujo1 nulls and are reported in em -1 To Procedures. (1.10 mmol) Cp*HfH condensed in 15 ml petroleum ether at -78°C was to room the solution was stirred for one hour, then 1.16 temperature, 2 0. 500 g mmol allene. After warming concentrated to ca. 5 ml and cooled to -78 0 C. Filtration and of drying in vacuo afforded 0.338 g (62%) white, crystalline Cp2Hf(H)Cn 3 -cH CHCH > (3). IR: 1648, 1615(sh), 2 2 1583, 1530, 1490, 1268, 1212, 1023, 1005, 850(st), 812, 740, 710, 653. 7.39. Found: C, C, 56.22; H, 7.31. 56.26; H, 42 Structure Determination for Cp2Hf<H><n 3 -cH 2 CHCHt (3). A large single crystal obtained by slow crystal- lization from Q-octane solution was mounted approximately along the b-axis in a glass capillary under N • A series of indicated 2 oscillation monoclinic and symmetry; Weissenberg the space photographs group P2 / c was 1 in£ erred Data from systematic absences in the diffractometer data. were collected on Syntex locally-modified a diffractometer with graphite monochromator. The unit cell parameters least (Table II) were obtained by squares refinement of 15 26 values (39 < 26 < 45°), where each 2e value was an average of two measurements of ±26. Intensity data was corrected for a 2% linear decay, as indicated by the three check reflections, and the data were reduced to F02 ; the form factors for H are from Stewart et. al, 18 and reference 19 for corrected for the other a toms, and that for Hf was The details on data anomalous dispersion. collection are included in Table II. The position Patterson map, of the Hf a tom was derived from the and a series of Fourier maps phased on Hf revealed the remaining non-hydrogen atoms of the molecule. Least-squares refinement of atom coordinates and U's, All ring methyl H-atoms and the hydride were located from difference maps. Allyl H-a toms were not reliably located and were placed at trigonal positions All H-atoms except the in the allyl carbon plane. hydride were introduced into the 43 model with fixed coordinates and isotropic U's. Refinement of anisotropic u all carbon atoms in the Hf complex with 1 j~s, and the hydride atom with isotropic U using all the data (3716 reflections) led to R = 0.049 and S = 2.51, with refinement of 0.10(2)Xl0- 6 . secondary extinction giving coeff. = The final ~F map showed a symmetric pair of peaks associated with the Hf atom (-2e-;1 3 , 1.2 A from Hf). Bond distances and bond angles are given in Tables III and IV, respectively. Final atomic coordinates and Uij's are given in Table VII. Hydrogen atom coordinates and u's are given in Table VIII. All calculations were carried out on a VAX 11/780 computer using the CRYRM system of programs. 44 ~stal TABLE I:I . and Intensity Collection Data for ep2Hf(H) (n3-ca2CHCH ) (3). 2 Fonnula Formula weight C23H36Hf 491.03 g/roo1 a P2 /c 1 8.7533(16) .A b 14.165(4) A c 17.5438(21) A s 104.810(12) 0 3 2lo3.o<a> A Space group 0 0 v z 4 0 3 1.55(1) g/an A 0.45 X 0.50 X 0.53 o. 71069 X (r.t)K£i) 4.92 nrn-1 calc Ccystal size l..l 28 1irnits, scan rate, 1.0° below Ka , 1.0° above Kct 1 2 3-30° 3.91°/min 1.0 1179(+h,+k,~1) backgrd tim=/scan tim=, 30-40° 2.02°/min 1.0 1303 (+h,+k,~1) number of reflections 3-30° 3.91°/min 1.0 1981 (+h,~k,~1) 29-40° 2.02° /min 1.0 2799 (+h,~k,~1) 39-50° 2.02°/rnin 1.0 3928 (+h,~k '~1) Scan range Total nurrber of averaged data 3716 (3537 F2 > 0) Refinement on ~0 0 Final number of pararreters 221 Final agreenent R (F2 > 0) 0.049 (3537)t 0 R' 0.039 (2885) s 2.51 (3716} t Typical R-va1ue, number of reflns used in sums given in parentheses. R' refers to R-value· calculated for reflns with F2 > 3aF2· 0 goodness of fit. S is the 45 * 3 Table III. Bond Lengths for Cp Hf(H) (n -CH 2 CHCH ) 2 2 aR 1 0 (A). Hf-H 1.85(7) C(14)-C(15) 1.396(12) Hf-C(1) 2.381(15) C(11)-C(11M) 1.520(15) Hf-C(2) 2.481(17) C{12)-C(12M) 1.4n5(16) Hf-C(3) 2.566(17) C(13)-C{13M) 1.486(18) Hf-C(11) 2.537(9) C(14)-C(14M) 1.496(15) Hf-C(12) 2.532(9) C(15)-C(15M) 1.516(14) Hf-C(13) 2.563(10) C(21 )-C(22) 1.396( 11) Hf-C(14) 2.554(9) C(21)-C(25) 1.387(12) Hf-C(15) 2.523(8) C(22)-C(23) 1.361(12) Hf-C(21) 2.509(8) C(23)-C(24) 1.408(15) Hf-C(22) 2.488(7) C(24)-C{25) 1.428{14) Hf-C(23) 2.563(10) C{21)-C(21M) 1.495(13) Hf-C(24) 2.560{11) C{22)-C(22M) 1.518(1?J Hf-C(25) 2.526(9) C(23)-C{23M) 1.511(16} C{1)-C(2) 1.388{23) C(24)-C(24M) 1.516(17) C(2)-C(3) 1.334(24) C(25)-C(25M) 1.492(15) C(11)-C(12) 1.390(12) Hf-<~R1 2.243 C(11)-C(15) 1.383(12) Hf-R2 2.233 C(12)-C(13) 1.457(13) Hf-A 2.253 C(13)-C(14) 1.397(14) = ring centroid of first Cp*-ring [atoms C(l1)-C(l.5~1)]; R2= ring centroid of second Cp*-ring [atoms C(21)-C(25M)]; A= centroid of allyl group [atoms C(1)-C(3)]. 46 Table IV. (IR1-Hf-R2 137.5 C( 11M)-C( 11 )-C(15) 125.7(8) A-Hf-Rt 111.5 C( 12M)-C( 12 )-C( 13) 126.3(9) A-Hf-R2 108.6 C(12M}-C(12)-C(11) 126.2(9) H-Hf-Rt 97.9 C(13M)-C(13)-C(14) 126.6(10) H-Hf-R2 92.9 C( 13M)-C(13 )-C( 12) 125.0(10) H-Hf-A 93.5 C(14M)-C( 14 )-C( 15) 126.4(9) H-Hf-C(1) 124(2) C( 14M)-C( 14 )-C( 13) 124.3(9) H-Hf-C(2) 92(2) C( 15M)-C( 15 )-C( 11) 127 .1(8) H-Hf-C(3) 66(2) C(15M)-C(15)-C(14) 124.0(8) C(1)-C(2)-C(3) 125.1(20) C(21M}-C(21 )-C(22) 126.5(7) C( 15)-C(11)-C(12) 110.0(8) C(21M)-C(21)-C(25) 124.0(8) C( 13}-C( 12)-C(11) 106.1(8) C(22M)-C(22)-C(23) 123.2(8) C( 14 )-C(13)-C( 12) 107.0(10) C(22M)-C(22)-C(21) 125.9(7) C(15)-C(14)-C(13) 108.7(8) C(23M)-C(23)-C(24) 123.0(9) C(11)-C(15)-C(14) 108.1(7) C(23M)-C(23)-C(22) 127 .8(9) C(25)-C(21)-C(22) 107.5(7) C(24M)-C(24)-C(25) 123.4(10) C( 23 )-C( 22 )-C( 21) 109.7(7) C(24M)-C(24)-C(23) 129.8(10) C( 24 )-C( 23 )-C( 22) 108.3(8) C(25M)-C(25)-C(21) 125.5(9) C(25}-C(24)-C(23) 106.5(9) C(25M)-C(25)-C(24) 125.8(9) C(21)-C(25)-C(24) 107.9(8) C(11M)-C(11)-C(12) 122.5(8) CJR 1= ring centroid of first Cp *-ring [atoms C{ 11 )-C( 15M)]; R2= ring centroid of second Cp *-ring [atoms C(21)-C(25M)]; A= centroid of allyl group [atoms C(l)-C(3)]. 47 Table v. Atom a Least-squares planes of pentamethyl rings for 3. Deviation from plane(A)b C(ll) C(12) C(13) C(14) C(15) C(llM) C(l2M) C(13M) C(l4M) C(l5M) 0.0173 -0.0143 0.0064 0.0037 -0.0130 0.4006 0.2056 0.3061 0.1846 0.1483 C(21) C(22) C(23) C(24) C(25) C(21M) C(22M) C(23M) C(24M) C(25M) 0.0124 -0.0171 0.0147 -0.0067 -0.0035 0.3807 0.1793 0.2742 0.1131 0.1809 aPlanes defined by atoms C(ll)-c(15) and C(21)-c(25). bA negative deviation is a deviation toward the metal atom. 48 Table VI. Intramolecular non-bonded distances for 3 (A)a C(l)--c(l2) 3.19(2) C(2)--c(23M) 3.30(2) C(l)--c(l3) 3.15(2) C(3)--c(l3) 3.36(2) C(l)--c(23) 3.09(2) C(ll)--c(21) 3.38(1) C(l)--c(23M) 3.21(2) C(llM)-c(21M) 3.25(2) C(l)--c(l2M) 3.44(2) H-c(l4) 2.66(7) C(l)--c(l3M) 3.40(2) H--c(24) 2.79(7) c (2 ) --c ( 2,3 ) 3.11(2) H-e (25) 2.47(7) C(2)--c(24) 3.19(2) H--c(25M) 2.74(7) H--c(3) 2.48(7) aListed are all c--c distances less than 3.50 Aand 0 hydride--c distances less than 2.80 A. 4 Table VII. Final non-hydrogen atom coordinates (x 10 ) X u z 4 and Gaussian amplitudes (x 10 ) . Uu u~ U33 u.~ Uu u~3 Hf 2777.7(4) 1980.0(2) 1711.2(2) 393(2) 453(2) 345(2) 81(2) 138(1) -4(2) C(1) 26{14) 1700{13) 1532(8) 514(66) 1851(159) 910(93) 306(88) 216(62) 511(99) C(2) 176(17) 2644(14) 1751(9) 880(99) 2005(186) 999(107) 936(121) 580(87) 612(123) C(3) 1113(22) 2974(12) 1628{142) 854(88) 1264(133) 711{103) 217(100) H 3865(80) 2983(49) 2421{8) 1855(161) 414. 2280{37) C(l1) 4351(11) 464(6) 2042{4) 732{62) 470(48) 337(41) 167(45) 187(42) 63(36) C(12) . 2875(11) 281{6) 2170(5) 567(55) 439{49) 464(49) -143{42) -52{41) -15{38) C(13) 2785(11) 846(8) 2851(5) 664(64) 982(79) 534(55) 160(60) 342{50) 295(55) C(14) 4189(12) 1361{6) 3077(5) 758(65) 483{51) 352(44) 32(47) 123( 44) -8(36) C(15) 5134(9) 1136(6) 2571{5) 378(44) 548(53) 473( 46) -22(39) 39{37) 114{40) C(l1M) 5104(18) -179(8) 1544(6) 1690(131) 647(69) 742(73) 489(80) 559{82) 120{56) C(12M) 1800(19) -483(9) 1815(7) 1614(137} 842(87) 878(87) -559(91) -348(89) 203{67) C(13M) 1602(17) 713(12) 3317(8) 1155(108) 1863(157) 1224(108) 659{106) 853(94) . 854(106) C{14M) 4663(19) 1945(8) 3810{5) 2034(149) 734(68) 346(47) 139(96) 47(68) -91(54) 1190(97) 948(84) -101(62) -34(58) 475(72) C(15M) 6827(12) 1464(9) 2691(7) 498(61) C(21) 4178(9) 2115(6) 634( 4) 528(47) 495(52) 347(38) 56(41) 161{34) 76(36) C(22) 2636(8) 1822(5) 282( 4) 263(35) 413(47) 454( 42) -15(33) 46(31) 52(34) C(23) 1612(12) 2542(8) 293(5) 620{61) 812(68) 386( 47) 11(54) 33(44) 106(47) C(24) 2477(16) 3311(7) 696(5) 1337(104) 479{57) 457(52) 351(60) 327(62) 175(41) C(25) 4097(11) 3029(7) 904(4) 726(59) 57 4(52) 385( 42) -131(57) 91( 40) 73(46) C(21M) 5664(11) . 1663(7) 543(5) 602(59) 897(75) 588(56) 204(52) 269(48) 276{49) C(22M) 2166(13) 926(8) -194(5) 952(81) 885(74) 411( 49) 93(67) 24(51) -141(52) 232(71) 514(62) 1558(117) 712(70) 184(69) -18(54) 4301(8) 822(7) 2166(171) 679(78) 882(85) 629(96) 625(100) 301(64) 3657(8) 1233(7) 1125(100) 802(80) 850(79) -489(74) 95(72) -30(62) C(23M) -105(13) 2614(10) C(24M) 1932(20) C(25M) 5476(16) •Refined with isotropic U. -157(7) ~ ~ 50 Table VIII. Hydrogen atom coordinates (x 10 3 ) X H(1A) H(1B) H(2B) H(3A) H(3B) H(1) H(2) H(3) H(4) H(5) H(6) H(7) H(8) H(9) H(10) H(11) H(12) H(13) H(14) H(15) H(16) H(17) H(18) H(19) H(20) H(21) H(22) H(23) H(24) H(25) H(26) H(27) H(28) H(29) H(30) y z and U' s u 1505 1039 76 -669 1219 1866 76 621 3071 1392 76 -451 3625 2528 76 1135 1743 2546 2794 76 4265 -440 1085 63 5667 -708 1845 63 5851 187 1314 63 679 -240 1607 63 2094 -750 1340 63 1781 -1000 2176 63 1173 3169 63 714 64 3223 63 1131 2093 775 3890 63 1630 4229 63 5435 3697 2092 4003 63 5094 2569 3697 63 7587 1024 3032 63 6983 2102 2954 63 1526 2184 63 7102 5555 956 538 63 979 63 6570 1837 39 63 1851 5873 1055 962 -515 63 836 -566 63 2851 363 146 63 2291 3181 -492 63 -295 2048 -511 63 -441 2635 205 63 -798 4783 2690 713 63 876 4441 477 63 1897 4395 1379 63 6328 3309 1634 63 5218 4232 1490 63 5995 3866 812 63 (A 2 ,x 10 3 ). 51 References (1) (a) Parshall, G. W. "Homogeneous Catalysis", Wiley-Interscience, New York, 1980, pp. 35-37. (b) Tulip, T. H.; Ibers, J. A. 1979, 101, 4201. J. Am. Chern. Soc. ( c > Bingham, D.; Hudson, B.; Webster, D.; Wells, P. B. J. Chern. Soc. Dalton 1974, 1521. (d) Keirn, w. "The rr-Ally1 System in Catalysis" in Schrauzer, G. N., Ed., "Transition Metals in Homogeneous Catalysis", Marcel Dekker, 1971, pp. 59.92. · (e) Orchin, M. Adv. Catal. 1966, 16, 1. (2) (a) Erwin, D. K., Ph.D. Thesis, California Institute of Technology, 1979. (b) Sanner, R. D.; Erwin, D. K.; Cohen, S. A.; Roddick, D. M.; Santarsiero, B. D.; Bercaw, J. E., manuscript in preparation. (3) Using the Eyring equation, with k (exchange rate c at coalescence temperature (sec- 1 >> calculated from 1T the Gutowsky-Holm relation: kc =-{2 - t::.v I• Gutowsky, H. S.; Holm, C. H. J. Chern. Phys. 1956, 25, 1228. (4) Calculated using values Tc = -a 0 c, 6 v (5) Sanner, R. D.; Manriquez, J. M.; Marsh, R. E.; Bercaw, J. E. (6) J. Am. Chern. Soc. 1976, = 9.7 Hz. ~' 8351. Moore, E. J., Ph.D. Thesis, California Institute of Technology, 1984. 52 (7) Incipient formation of an n 1 -co>allyl complex has been suggested for the structurally characterized iridium n-allyl complex [Ir<n 3 -c 3 a 5 >Cl(C0)(P(CH > 3 2 9 Ph>2J [PF 6 ] , although bondlength variations are only possibly significant. (8) (a) Erker, G.; Rosenfeldt, F. Ed. Engl. 1978, 17, 605. Angew. Chern. Int. (b) Ibid., J. Organomet. Chern. 1980, 188, C1. (9) Kaduk, J. A.; Poulos, A. T.; Ibers, J. A. J. Organomet. Chern. 1977, 127, 245. (10) Helmholdt, R. B.; Jellinek, F.; Martin, H. A.; Vos, A. <11) Rec. Trav. Chim. Pays-Bas 1967, 86, 1263. Pauling, L. "The Nature of the Chemical Bond"; Cornell, New York, 1960; 3rd ed., pg. 256. (12) Bernstein, E. R.; Hamilton, w. C.; Keiderling, T. A.; Kennelly, W. J.; Laplaca, S. J.; Lippard, S. J.; Marks, T. J.; Mayerle, J. J., unpublished results at Brookhaven National Laboratory (neutron structure). (13) Johnson, P. L.; Cohen, S. A.; Mark, T. J.; Williams, J. M. J. Am. Chern. Soc. 1978, 100, 2709 (neutron structure). (14) This thesis, Chapter 4. <15) Santarsiero, B. D.; Moore, E. J.; Bercaw, J. E., 1982, unpublished results. (16) This thesis, Chapter 1. See also reference 6. 53 (17) Roddick, D. M.; Fryzuk, M. D.; Seidler, P. F.; Hillhouse, G. L.; Bercaw, J. E., manuscript in preparation. (18) Stewart, R. F.; Davidson, E. R.; Simpson, W. T. J. Chem. Phys. 1965, 42, 3175. (19) International Tables for X-Ray Crystallography, Vol. IV, 1974, pp. 72-98. 54 Chapter III Reactions of Permethylhafnocene and Permethylzirconocene Hydrides with CO. Synthesis and Reactivity Patterns of Early Transition Metal Aldehyde Complexes. 55 INTRODUCTION Transition metal-mediated C-C bond-forming reactions, particularly those involving carbon monoxide and/or simple olefins, are of continuing interest in organometallic . 1 c h em1stry. Recently, the ability of early transition metal complexes to effect a variety of stoichiometric c-c bond-forming transformations has received much attention. In particular, hydrozirconation 2 and titanocene methylene transfer, 3 which have been investigated in detail, have proven to be of considerable synthetic utility. Work in our laboratories 4 has established a number of CO-based carbon-carbon coupling reactions (equations 1-5 ) (I) /co Cp2 Zr '-c-ozrcp*2 I H (2) I H (3) 56 (4) for group IV permethylmetallocene complexes. The reaction of with zirconium noteworthy: alkyl hydride derivatives CO is labeling studies have shown that carbonylation cp *2 Zr(H)CH CHMe proceeds via the intermediacy of 2 2 aldehyde complex 2 (Scheme I), which undergoes facile 8-H of elimination to form the enolate hydride product 3. • t3-H elim• 2 Scheme I • This 57 pattern of reactivity is unprecedented in late metal aldehyde chemistry, and was therefore of interest to us. The ready availability of a range of alkyl as well as aryl and alkenyl hydride complexes of zirconium and hafnium 5 has provided the opportunity chemistry of zirconium in detail. chapter. ~nd to examine the carbonylation hafnium hydrocarbon derivatives The results of this study are reported in this 58 RESULTS (1) 2 Synthesis and Reactivity of Cp2M(CO><n -O=CHR>(M=Zr, Hf; R=CH CHMe , Ph). 2 2 Toluene solutions of Cp2M(H)CH CHMe 2 2 (M=Zr, Hf) are quantitatively converted at -50°C under 1 atm co to the 2 Cp2MH<n -c<O>CH 2 CHMe > 2 1 Characteristic H NMR (Table!) and corresponding dihaptoacyl hydrides, (M=Zr : la; Hf : lb>. 335.86 o) spectra of lb are indicative of a single isomeric species at low temperature, presumably the expected kinetic product with acyl oxygen coordinated in the lateral equatorial position. 6 co~ o~ /C~CHMe 2 "f"C CP2*M/ , (6) H ( M = Z r: I a; Hf: I b) The reaction of at 25°C has been Cp2ZrH(OCH=CHCHMe of Cp2Zr(C0> . 4 b 2 2 Cp~Zr(H)CH reported > to 2 CHMe 2 with carbon monoxide give the enolate hydride, (3), together with a small (-5%) amount However, when solutions of la and lb are stirred vigorously in toluene at -78°C under 1 atm CO and allowed to warm slowly to room temperature over the course 59 new products 4a and 4b <- 80% pure by 1 a of several hours, NMR, with traces byproducts) are of enolate obtained, hydride which may and be dicarbonyl isolated from hexamethyldisiloxane as highly soluble, orange powders. and 13 c NMR chemical and infrared reactivity data, clearly 1 a as well as subsequent indicate 4a and 4b to be 2 n -aldehyde complexes as shown below: 8 (M = Zr:4a; Hf:4b) The 1 5 a NMR spectrum of 4b exhibits inequivalent n -c cca > 5 3 5 o ( lH, o ClSH) and 1.71 6 ClSH), a broad 3 JHH = 10 Hz) assigned to the and overlapping methyl resonances at 1.67 doublet at aldehyde proton, 1.18 2. 21 an o and 1. 20 o ( 3JHH = 6 Hz) isobutyl methyl groups. prepared from coupling < <252.49 o> and 156.2 Hz) 2 = Jcc aldehyde carbons. given structure. 9.8 7 Hz) 13 between data doublets at c NMR of labeled 4b, 13 and carbonyl These of due to the diastereotopic The gated Cp2Hf(H)CH CHMe 2 2 pair a shows 84.22 o; consistent small carbonyl terminal (dd, are co, 1 JHC with = the The aldehyde proton and carbonyl carbon 60 chemical shifts reported for are free substantially aliphatic upfield from 8 aldehydes; values however, the chemical shift of the aldehyde carbon in 4b agrees closely with the value reported for the structurally characterized 2 n -aldehyde molybdenum complex (81.6 8). 9 methylaminobenzyl><n2-0=CHPh) The infrared spectra of showing 19 30 em strong -1 lower , that (2036 cm- 1 >, 10 of and 4a and 4b are carbonyl respectively. than symmetric terminal CpMo(CO) ( a -2-pyridyl-2- These bands values at are 1940 and significantly Hf(IV) the quite similar stretching modes informative, to values 1 of Cp2Zr I<CO) 2 for ( 1942 cm- the 1 11 > P5 Hf II ( CO ) 2 ( 19 4 0 em-1 ) , 4e suggesting a consider a b 1 e and C amount of electron rich M(II) character (canonical form A) in 4a and 4b. bands in However, 4a,b above the absence of any additional IR 1200 cm-l assignable to an aldehyde acyl stretch v<C-0) is noteworthy, 12 and appears indicative of some degree of M( IV) oxymetallacyclopropane character (canonical form B). Both 4a and 4b decompose slowly at 25°C, stored indefinitely ligand is quite at low 13 labile: indicated complete label - at room temperature (P(CO) temperature. co labeling but may be The carbonyl studies of 4b scrambling after several minutes ~ 2 atm): (7) 61 The lability of CO in 4a is suggested by its thermolysis (80C, 1 hr}, which induces clean loss of CO to generate the enolate hydride, 3. In contrast, thermolysis of 4b at 80°C for 1 hr effects a clean rearrangement to a identified by 1 H and 13 c NMR and new species, IR data as the cyclic enediolate Cp2HfOC(CH CHMe >=CHO (5} (equation 8>. 2 13 2 5 When toluene solutions of 3b are cooled below -10°C in the presence of 1 atrn CO, a dramatic, reversible color change from orange to lime green is observed. 1 H NMR of this green solution indicates a quantitative conversion of 4b to a single new species In 6. contrast, 6 is not observed in the variable temperature 1 H NMR of 4b under N • 2 Likewise, the 1 H NMR of 4a under N temperature or CO is essentially 2 independent. The 1 a NMR of 6 shows the resonance previously attributed to the aldehyde proton in 4b shifted downfield to 4.88 cS (dd, 3 JHH = 10.1, 2.7 Hz); the remaining ring and isobutyl methyl resonances in 6 are only slightly shifted from values in 4b (Table I}. The 13 c NMR of 13 co-labeled 4b treated with 13 co at -50°C is more informative, resonances at 94.4 showing the o (dddd, presence J CC = 13. 6, of three 3 7 .1 Hz; labeled 62 3 136.7 Hz; JCH = 5.9 Hz), 213.6 8 (d, Jcc = 37.1 Hz>, and Treatment of Cp~Hf< 13 co>­ <o=13cHcH2CHMe2> at -50°C with 12 co yields a product with 310.6 o (d, Jcc = 13.6 Hz). only the 94.4 and 213.6 pm resonances enriched, indicating that the 310.6 A final o carbon is derived from ambient CO uptake. piece of spectroscopic data is given by the low temperature infrared spectrum (toluene, -78°C) of 6, which shows two strong acyl bands at 1724 and 1640 cm-l and no bands in the 1800-2100 em -1 region. Despite the extensive spectroscopic data, no clear assignment of the structure of 6 is evident. A reasonable structure consistent with all the available data is given below: 6 The isolation of aldehyde carbonyl complexes 4a and 4b is plagued by impurities and low yields. In order to obtain more suitable systems for study, the reaction of CO with a variety of alkyl hydrides, Cp2M(H}R (M=Zr, Hf; R=Et, butyl, ethyphenyl, neohexyl, neopentyl) was examined. Not surprisingly, all alkyl hydrides reacted similarly with CO, generating complexes analogous to 4 in varying yields 63 similar with (40-80%), instabilities thermal and intractable natures. The reaction of CO with Cp2Hf(H)Ph was examined in the hope of cleanly forming a stable aldehyde product not subject to S-H Solutions of elimination decomposition pathways. Cp2Hf (H) Ph react surprisingly slowly with 3 atm CO over the course of several hours at 25°C to form (>95%, 1 H NMR) the benzaldehyde carbonyl Cp2Hf(CO><n 2 - 0=CHPh) (7), isolable in 66% yield as an analytically pure, thermally stable orange crystalline solid. co The monomeric formulation (9) of 7 was confirmed by its solution molecular weight <c 6 o6 , calc: 583; found: 592). Monitoring reaction 10 by 1 H NMR indicated no build up of an intermediate carbonyl adduct or acyl hydride species. Thermolysis of 7 (80°C, 12 hr) induces clean rearrangement to an enediolate complex analogous (8). to 5, Cp2HfOC (Ph) =CHO In contrast to 4b, no spectral changes are observed when solutions of 7 are cooled under excess CO. 64 (2) Reaction of Cp2HfCH cH cH cH with carbon monoxide. 2 2 2 2 A reaction related to equation 6 is the carbonylation of Cp2ZrCH 2 cH 2 cH 2 cH 2 to give Cp2Zr(H)OC=CHCH 2 ca 2 ca 2 , 4 b. reaction and 2 hope Since 2 are 2 2 Cp~HfCH cH ca ca reaction of the reaction of preparing a the cyclic enolate hydride, 2 the mechanisms believed (9) to be of this similar, the with CO was examined in coordinated ketone complex, analogy to the aldehyde complexes 4a,b and 7. in The reaction of Cp2HfCH 2 cH 2 ca 2 cH 2 with excess CO was monitored at low temperature by 1 a and 13 c { 1 H } NMR. At -50°C, resonances for 9 were attributed to replaced by the acyl complex, a new set of resonances Cp~Hf ( n 2 -o=CCH 2 cH 2 cH 2 cH 2 ) The identity of 10 was confirmed by 13 c { 1 H} NMR of <10). the slowly 13 co field labeled complex, resonance at functionality. 344 When which exhibited o characteristic of solutions of 10 are a single low a dihaptoacyl warmed slowly under CO, a single, isolable product is obtained, which NMR and IR <v <C=C): 1640 cm- 1 ; be not the desired v(C-0): 1210 cm- 1 > data show to n2 -cyclopentanone complex, but rather (I 0) 9 10 II 65 Reactions of Cp~ZrH<n 2 -o=CCH 2 cHMe > with c ~ L2 2 4 (3) 2-butyne, H2 and t-butylacetylene. The demonstrated ability of n 2 -aldehyde complexes 4b and 7 to readily couple their aldehyde and terminal carbonyl ligands suggested that similar reactivity might be observed in complexes sui table substrates. where CO is replaced Attempts to trap by other in-situ generated zirconium aldehyde intermediate Cp2Zr<n 2 -o=CHCH 2 cHMe 2 > (2} by slowly warming solutions of acyl hydride la in the presence of large excesses of methylisonitrile or pyridine yielded no isolable toluene solutions of products. However, la with at -42°C treatment excess c H 2 4 of and 2-butyne did quantitatively yield upon slow warming to 25°C the heterometallacycles Cp; ZrOCH ( CH 2 CHMe 2 ) CH CH 2 2 Cp;zrOCH(CH 2 CHMe 2 )C(CH 3 >=C(CH 3 > (13), ( 12) and respectively (equation 11). 12 (II) MeC!!: CMe Ia ~ Pj'Y Cp~Zr~ 13 66 The structures of 12 characteristic 1 H and 13 c and 13 were confirmed by NMR data. In particular, the spectral data for 12 compare closely to those reported for 2 the related titanium complex Cp~TiOCH(CH 3 >cH ca 2 , 14 with 6 highly coupled proton resonances c 1 H, 500.13 MHz) observed for the ring moiety. Both 12 and 13 were isolated as analytically pure white solids. An precursor additional la is !-butylacetylene hydride mode of indicated by upon slow Cp2Zr(H)OCH 2 cH 2 CHMe 2 reactivity its reactions warming (14> for to and aldehyde with produce alkoxy H and 2 alkoxy acetylide Cp2Zr<c=ctBu)OCH 2 cH 2 CHMe 2 (15), respectively (equation 12>. 14 (12) HC==CCMe3 Ia 15 67 14 was isolated in good yield as a brown sublimable solid. Both 14 and 15 exhibit nearly identical 1 H NMR resonances attributable to the alkoxy moiety. The hydride resonance for 14 appears as a broad singlet at 5. 69 o , a relatively high field chemical shift characteristic alkoxy-substituted hydride complexes. 4 b,e as a fairly pure (>90%, 1a of 15 was isolated colorless NMR), zirconium oil. The infrared spectrum reveals a 2040 cm-l band assigned to the terminal acetylide group. (4) Reactions of Cp2Hf(H)CH=CHtBu with CO. Like the alkyl hydride complexes examined thus far, the o-alkenyl readily with 1 hydride complex atm at . -78°C CO hydride, Cp2Hf (H) <n 2 -0CCH=CH tau) Cp2Hf(H)CH=CHtBu to ( 16). form the reacts vinylacy1 The characteristic low field acyl carbon chemical shift ( 320.45 o ) and large vinylic proton dihaptoacyl coupling structure stereochemistry about constant analogous the of 15.1 to 1b, Hz with carbon-carbon suggests a the trans double bond preserved. (13) 16 68 Thermolysis of rearrangement tBu) 16 to > (T form a -10°C> in vacuo new metallacycle, induces a Cp2HfOHC=CHCH- (17>, isolable as a thermally unstable orange oil. .,.,c-c 0 / C *H( P2 ' H ;o......._c/H • \ c. . . . . CMe 3 H H/ I CpfHf (14) H~c'H CMe3 17 16 The structure of 17 is clearly established by spectroscopic data, and by Specifically, 25°C its subsequent further treatment of yields the quantitatively chemical 17 with reactivity. excess CO at insertion product, Cp*~f(OCH=CHCH(tBu)(CQ) (18). 2 co (15) 17 18 may 18 be isolated crystalline solid. from petroleum ether as an orange The 1 H NMR of 18 closely resembles that of 17, the most notable difference being a downfield shift of the resonance assigned to the a-proton in 17 to 2.90 (pseudo triplet, JHH = 6 Hz). o Correct assignment of the 69 coupled highly vinylic tertiary and carbon proton resonances was verified by carbonylation of the deuterium labeled Cp2Hf{D)CH=CDtBu to give {18d). The an n2 -acyl presence of Cp2HfODC=CHCD(tBu)C0 functionality is indicated by IR <v<C-0): 1610 cm- 1 > and 13 c NMR of the 13 co labeled compound (£{acyl), 307.25 The acyl temperature, formal 1,2 but o). metallacycle 18 is upon to 80°C hydrogen warming shift to give stable at room rearranges the via a ring 7-membered metallacycle, Cp2HfOCH=CHC(tBu)=CHO (19). (16) 19 18 The thermal rearrangement of 18 to 19 obeys first-order kinetics for greater than three half lives (Figure 1), with k = 1.5 deuterium X 10- 4 sec-l at labeled complex 80°C. 18d, The thermolysis which produces of the solely Cp2HfOCD=CHC(tBu)=CDO, is somewhat slower, giving a kinetic isotope effect of kH/k 0 = 3.6. 70 Figure I ..•• :I c i 71 DISCUSSION The differs reaction markedly transition chemistry of from metal that acyl of acyl hydrides previously and reported lb late typically which hydrides, la decarbonylate and subsequently release alkane, 15 or, in one instance, undergo This difference reductive in elimination of aldehyde. 16 reactivity may be readily ascribed to the oxophillic nature of coordinatively unsaturated group IV metallocenes, which encourages n 2 11 oxycarbenoid 11 acyl coordination and directs reactivity toward final products which contain metal-oxygen bonds. The facile migration of hydride to the acyl carbon in la to form a reactive, n-bound aldehyde species, implied by earlier labeling studies, has been verified by trapping of the formally sixteen electron intermediate with CO to give an isolable aldehyde carbonyl product, has proven general for a 4a. This reaction number of zirconium and hafnium alkyl and aryl hydride complexes. 17 The rates of reaction of the acyl hydride la with CO and other trapping ligands are independent of the nature and concentration of substrate, suggesting that the products formed evolve from a common reactive intermediate, 2 (equation 17). 0 ·r'/'...,/ ; /c t -30°C Cp~Zr, • L • Products H Ia (17) 72 The relatively electron rich nature of 2, IR data for the carbonyl adduct 4a, reactivity patterns observed. c 2a 2-butyne (equation 11) 4 and The is as suggested by reflected in the of la with analogous to the reactions are reported reactions of [Cp Ti<n 2 -c<O>=CH 2 J 2 , Cp2Zr(Pyr><n 2 2 (CO)=CH >18 and [Cp zr<n 2 -C(O)Ph >J 19 with olefins and 2 2 2 2 acetylenes, and complement the reaction of Cp2Ti<C 2 H4 > with acetaldehyde: 20 , 21 in . each case, facile oxidative coupling is observed to form stable, complexes (Scheme II) . Scheme II M(IV) oxymetallacyclopentane 73 Similarly, the reactions of la with H2 and ac=ctBu are best viewed as simple oxidative addition reactions, with subsequent hydride transfer to the electrophillic carbonyl center giving the observed alkoxy products (Scheme III). X= H, C=CR Scheme Ill The observed coupling of carbonyl and aldehyde ligands in 4b to give the enediolate complex 5 (equation 8) is unusual. A reasonable mechanism to account transformation is given in Scheme Iv. 22 for this Here, CO inserts into the reactive Hf-C(aldehyde) bond to form an oxyacyl- metallacyclobutane which formal 1,2 complex hydrogen shift 20, to the then undergoes carbenoid-like 23 a acyl 74 fast 20 /.,2 H / 5hitt Scheme IV carbon leading to the observed product. dented, an intermediate analogous by Schrock 24 in Though unprece- to 20 has been proposed the carbonylation of cp*TaMe <n 2 -c<O>Me > 2 2 (equation 18) • C~ Me~ I Me-Ta-O co '\1 CMet - (18) Me 1,2 hydrogen shift reactions analogous to that proposed in Scheme III have been observed for thorium 25 and zirconium 6 c acyl complexes. Indeed, the thermal rearrangement of acyl 75 rnetallacycle 18 (equation 16 >, intermediate 20, exhibits a which models substantial the proposed kinetic isotope effect (3.6) consistent with a rate-limiting 1,2 H shift. This observation, of thermolysis together with the observed similar rates of and 4b 18, suggests that the rate limiting 1,2 H shift step in Scheme IV is reasonable. The reaction of 4b with CO at low temperatures lends further indirect support for the mechanism in Scheme IV. Although the exact nature known, 13 c NMR labeling incorporation of CO at without dissociation of aldehyde from of low temperature the carbonyl formed the rna s t indicate to form ligand in a 1 ike 1 y facile, in i t i a 1 /o, ~R ' c~ ~H ~0 . • 1,2y /o'c.PR M z .t.)c / 'J;.H 0 Shift lo......__c/ M R I \yC, 1I 6 H Scheme V 6 or not that occurs isover- reversible step reaction as well as reaction 8 (Scheme V). M-C~ is is coordina ti vely saturated, insertion to form 16 electron 20 eq u i 1 i b r i urn remains product experiments Since 4b 4b. the in this 76 The convenient in situ generation of highly reactive transition metal-aldehyde complexes following Schemes I and II represents Consequently, a potentially the extension useful and synthetic process. generalization of chemistry to other CO-derived oxygenate complexes this was of interest. The failure to observe a cyclopentanone adduct in the disappointing, is not surprising. Consideration of the steric requirements for binding ketone to a Cp2M moiety to form a a,a-disubstituted oxymetallacyclopropane complex suggests that such a complex would be highly destabilized relative to reactivity aldehyde observed complexes for 9 such parallels as and 4 ·that reported Cp*ZrMe 4 b and titanacyclobutane 18 complexes 2 7. The for (equations 3 2 and 19) . /OX< co Cp 2 Ti~Rl Cp2Ti 'O I R2 R2 Although product rationalized (19) Rl formation in terms of an in reaction 3 has been intramolecular coupling of a bis-oxycarbene complex (equation 20), the results (20) 77 presented in this chapter suggest an alternative pathway available for these coupling reactions (Scheme VI) similar to that proposed in Scheme IV. II • • •4 - • • 0 M..-11 R~~ • 1,2~ Shift Scheme VI The final step in the above mechanism entails a 1,2 alkyl shift to an acyl carbon center. Although alkyl migrations to early metal acyls have not been reported, the considerable steric strain present in B, S-disubsti tuted metalla- cyclobutane intermediate 21 26 may serve to induce greater acyl carbenoid character, _ resulting migration: in a more facile 1,2 78 'rhe thermolysis of presence of aldehyde carbonyl metallacycle excess CO the vinylacyl hydride 16 in the similarly failed complex analogous product obtained in to to 4. this generate an However, the reaction may be rationalized in terms of an intramolecular olefin trapping of an intermediate aldehyde complex 22, Scheme VII. Scheme VII 1t as outlined in 79 Coordination aldehyde 23, 27 of the complex followed 22 by vinylic to form group in a , B-unsaturated a n 4 -heterobutadiene species rearrangement to the observed product metallacycle 17 is anticipated to be facile in light of the highly fluxional behavior butadiene complexes. 28 exhibited by analogous hafnium TABLE I. 114ll 8 DAr A Compound Assignment Cp *ZrH(n 2-C(O)CH CHHe ) (la) 2 2 2 Cp *HfH(n 2-C(O)CH CHHe ) (lb) 2 2 2 Cp *Zr(CO)(n 2-DCHCH cHHe ) (4a) 2 2 2 Cp *Hf(CO)(n 2-DCHCH CHHe ) (4b) 2 2 2 Cp;Hf( 13 2 co)(n -o 13 CHCHHe ) 2 C5(C!!3)5 Chemical Shift 1 u NMR, -70°C 1.70 s C(O)CH CHHe 2 2 1.05 d C(O)C!! CHHe 2 2 2.37 d, br Zr!! 3.53 a, br c5 <C!!3> 5 1 u NMR, -l0°C J - 5.4 1.78 8 C(O)CH CHHe 2 2 1.12 d C(O)CH cllie 2 2 Hf_!! 2.50 d, br c5 <C!!3>5 Coupling J - 6.0 7.03 s 1 H NHR (X) 1.70, 1.75. 0 O•CHCH cHHe 2 2 1.23, 1.27 d J - 6.0 D-C!!CH CHHe 2 2 2.47 d, br J - 9.5 c5 <C!!3>5 1H NHI. 1.67, 1.71 s D-CHCH CHHe 2 2 1.18, 1.20 d J - 6.0 D-C!!_CH CHHe 2 2 o- 13-CHCH 2CHHe 2 2.21 d, br J - 10.0 Hf(lJfO) 13 c NKR 84.22 ddd 252.49 d 1 2 2 Jcu·156.2, Jcc·9.8, Jcu·8.o 2 Jcc • 9.8 TABLE I (cont'd) Compound ·,.------Cp2HfOC(CH2CHHe2)•CHO (') C •H;o13c(CH CHHe )• 1 j~b p2 2 2 c5 <C!!3> 5 1 H NMR 1.09 d OC(CH cHHe )·C~O 6.30 8 2 2 o c(CH 2 CHHe 2 )- 13 c~O 13 c5 <C!!3> 5 CH CHHe 2 uc NHR 1 H NHR, -14°C llfHO 13 c NHR, -30°C J - 6.0 1J 146.8 dd, br 1J •82.5, 2JCH•21.5 cc lll.6 dd lJ CH •177, 2 6.30 dd cc•82.5, JCH•21.5 1 J - 4.9, 4.9 4.88 dd J - 10.1, 2.7 94.4 dddd Jcc·13.6,37.1, 3 JCH•5.9 2 Cp;Hf(CO)(n -0CHPh) (7) 13£•0 2l3.6 d Jcc•37.1 13£-o 310.6 d Jcc•l3. 6 c5 <c~J> 5 1 H tHl JcH•177 1.64, 1.68 8 0.87, 0.93 d 2 llC_!!O Coupling 1.89 8 CH CHHe 2 2 13 13 o £(CH CHHe )• cHO 2 2 13 13 o c(CH CHHe )• cHO 2 2 (6) Cheaical Shift Assignment 1.57, 1.72 ~ OCHPh 7.02 .. OCHPh 7.33 m OCHPh 7.62 .. OC_!!Ph ),36 8 1 JCH•136.7, co t----J TABLE I (cont'd) ·~--=....,..-- Cp2HfOC(Ph)•CHO (8) Cp *u~~IJ~(Ph)• 2 13 1 H NHR c5 <C!!3> 5 CH~ 6.7-7.77 .. OC(Ph)•C!!_O 7. 34 8 o 13c(Ph)• 13c!!_O 7.34 dd o Cp *Hf(n 2 -occu cu cu CH ) (10) 2 2 2I 2 2I 13 (11) c NHR 13 c(Ph)• fHO 146.42 dd 134.73 dd 1 u NMR, -5o•c C5(<!!!3)5 0,23 II O•CCH 2C!! 2C!!2cu 2 1.93 .. D-CC!! cu cu cu 2 2 2 2 2.55 • llc{lul 1 C5(C!l3)5 H NMR 2 Jc 8·22.4 1 2 Jcc·83.5, Jcu·22.4 1 1 Jcc·83.5, Jcu·l76.3 Jcu·l76.3, (X) 1\.) 344 .o • 1.91 • 1.66 .. OCCH C!! C!!_ cu co 2 2 2 2 2.29 .. OCC!!2CH 2CH 2C!!2CO OfCH 2CH 2CH CHf:_0 2 1 1. 71 8 o-cCH 2cH CH C!!2 2 2 D-fCH cu cu cu 2 2 2 2 Cp HfOCCH cu cu cu co 2 2 2 2I 2 I 13 Coupling 1.87 8 OC(Ph)•CHO 13 0 f(Ph)• 13CHO •• Chemical Shift Assignment Compound 13 c NMR 139.82 • OC.£H CH CH~ co 31.85 t J - 125 OCCH 2.£Hf:_H 2cu 2co 24.32 t J - 125 2 2 2 TAILI I (cont'd) Compound Cp;ZrOCH(CH cHHe )CHH'CHH' (12)b 2 2 1 c5 <C!I3> 5 u NHR 4.51 ddt OCH(CH cHMe )CHH'CHH' 2 2 1.004. 1.006 d J - 6. 7 OCH(CH CHHe )C!!H' CHH' 2 2 2.65 dddd J - 12 . 5. 7.4. 3.3. 1 . 8 OCH(CH CHHe )CH!'CHH' 2 2 2.52 dddd J - 12.5. 12.5. 10.9. 6.4 OCH(CH cHHe )CHH'C~' 1.51 ddd J - 12.5, 12.5. 7. 4 0.12 ddd J - 12.5, 6.4, 1.8 78.20 d J - 139.1 2 2 2 OCH(CH CHHe )CHH'~' 2 2 OfH(CH cHHe )CHH'CHH' 2 2 13 OCH(fH CHHe )£HH'fHH' 2 2 13c{ 1H} c lHl OCH(CH~HHe )CHH'CHH' 2 cp;ZrOCH(CH CHHe )c(cH )•C(CH ) (13) 2 2 3 3 Coupling 1.85. 1.90 • O~(CH CHHe )CHH'CHH' 2 (H' cia to -thine H) Cheaical Shi'ft Aseign~~ent J - 10.9. 9.3. 3. 3 42.37, 49.98. 50.24 22.88, 24.11, 25.80 1 H NHR c5 <C!!3> 5 CX> 1.85. 1.87 • w OC!(CH CUHe )C(CH )•C(CH ) 2 2 3 3 4.77 d. br J - 11.2 OCH(CH CHHe )C(CH )-c(CH ) 2 2 3 3 1.04. 1.08 d J - 6.6 OCH(CH CHHe )c(~ )•C(CH ) 1.69 •· br 2 2 3 3 OCH(CH CHHe )C(CH )•C(C! ) 2 3 2 3 ~(CH CHHe )C(CH )•C(CH ) 2 2 3 3 1.59 • 13 c NHR OCH(£H CHHe )C(CH )•C(CH ) 2 2 3 3 OCH(CH CHHe )£(CH )•f(CH ) 2 3 2 3 2 3 3 OCH(CH~HHe )C(£H )•C(£H ) 82.3 d J - 133 46.6 t J - 125 152,1. 184.5 • 13C{1H} 24.1, 21.2. 19.9, 15.5 TABLE I (cont'd) Assignment Compound • Cp Zr(H)OCH 01 CHHe (14) 2 2 2 2 • C5(C!!3)5 Chemical Shift 1 u NMR 2 Cp;Hf(H)(n -C(O)CH-cHtBu (16) 4.13 t J • 8.0 OCH cu cHHe 2 2 2 0.90 t J • 6.0 Zr!! 5.69 8 C5(CIJ.3)5 2.00 8 c:ctgy 1.38 8 OC!!2CH2CHMe2 4.17 t J • 7.0 OCH cu cHMe 2 2 2 0.98 d J • 6.0 C5(C!!3)5 1 u NHR, -W°C 7.68 d J • 15.1 C(O)CH•C_!!tBu 6.59 d J • 15.1 C(O)CH•CHtBu 0.95 • Hf.!! 7.13 8, br C5(C!!3)5 13 1 c NHR, -W°C 320.34 8 u NHR 1.86, 1.89 8 t t ~ 6.46 dd J • 5.3, 3.0 OCH•C.!!CHtBu 5.20 dd J • 5.3, 6.0 QOfocCUC!!t Bu 0.45 dd J • 6.0, 3.0 1.30 8 13c NHR 137.32 d J • 1H.2 OCH•fHCHtBu 111,27 d J • 159.3 OCH•CHfHtBu 72.86 d J • 124.5 OfH•CHCHtBu • r ro OC!!•CHCHtBu OCH•CHCHtBu Cp Hf(OCU•CHCU( Bu)CO) (18) 2 1.90 8 C(O)C,!!•CHtBu f(O)CH•CHtBu Cp;Hf(OCH•CUCHtBu) (17) 1.95 8 OC!! 2CH CHMe 2 2 t Cp Zr(c:c Bu)OCH CH CHHe (15) 2 2 2 2 Coupling C5(C!!3)5 OC!!•CHCH(tBu)CO OCH•C!!CH(tBu)CO 1 u NHR 1.81, 1.87 8 7 .w dd J • 4.29 dd J • 6.0, 3.0 6.0, 3.0 TABLI 1 (cont'd) Assignment Compound Chemical Shift OCH•CHC!!(tBu)CO 2.90 dd OCH•CHCH(tBu)OO OfH•CHOI ( tBu) CO • .----- t J - 3.0, 3.0 1.30 • llc NHR 148.49 d J - 177 OCH•.fHCU ( t Bu) CO 103.64 d J - 161 OCH•OifH(tlu)ro 12.92 d J • 115 OCH•Oiat(tBu).£0 307.25 • r Cp Hf(OCH-cHC( Bu)•CHO (19) 2 Coupling C5(CH3)5 1 u NHR 1,91 • ~·CHC(tBu)•CHO 7.01 dd J • 7.2, 0.8 OCB~C(tBu)•CHO 4.33 dd J • 7.2, 0.9 OCU•CHC(tBu)•C!!O 1.05 a, br OCH•CHC(tBu)•CHO 1.23 • ~-cuc(tBu)•CHO OCH•fHC(tBu)•CHO OCH•CHf(tBu)•CHO OCH•CHC(tBu)•fHO (a)l 13 C (22.5 HHz) NKR spectra taken in benzene-~ at ambient teaperature; low temperature NHR spectra obtained in toluene-~. H (90 HHz) and Cbeaical ahifta are reported in 6 relative to internal THS or reaidual protona or carbona in solvent. Coupling constants are reported in Hz. Long range 13c-lu coupling ia reported only when a coupling constant could be deterained. (b)l H NHR spectrum obtained at 500 HHz. 00 U1 86 EXPERIMENTAL SECTION General performed using techniques. first Considerations. either Solvents from LiAlH 4 methyldisiloxane, All glove box manipulations or were purified then 2-butyne, and high by were vacuum line vacuum transfer from "ti tanocene". 29 Hexa- and 1-butylacetylene were 0 stored under vacuum over activated 4 A molecular sieves. Hydrogen was purified by passage over MnO on vermiculite 30 0 and activated 4 A molecular sieves. Ethylene and carbon monoxide were used directly from the cylinder. Elemental analyses were determined by Alfred Bernhardt and Dornis & Kolbe Analytical Laboratories. JEOL 1 H NMR spectra FX90Q, and Bruker were recorded 500 MHz spectra were obtained using a Infrared spectra spectrometer as are reported were in cm- 1 . spectrometers. JEOL measured nujol mulls, using Varian EM-390, 13 c NMR FX90Q spectrometer. on a Beckman 4240 unless otherwise noted, and Low temperature IR spectra for 6 were obtained using a low temperature IR cell designed by Hinsberg. 31 Procedures. .£E.;zr<g 2 -ocHCH 2 cHMe 2 > (4a). cp;zr<H>CH 2 CHMe 2 (0.55 g) A solution of in 10 ml toluene was cooled to -78°C, 1 atm CO was admitted, and the solution was allowed to warm slowly to room temperature with vigorous stirring over the course of several hours. Volatiles were removed 87 in vacuo and the resultant orange oily solid was taken up 80 mg of solid 4a (85% in ca. 5 ml hexamethyldisiloxane. 1 H NMR) pure, was collected, residue consisting largely leaving ( -70%) an oily filtrate of unisolated 4a. IR: 1940(st), 1160, 1027, 920, 845. Moderately pure ( 80-90%, 1 H NMR) 4b may be prepared following procedures described for IR: 1930(st), 1150, 1030, 4a. 927, Thermolysis of 842. crude 4b in benzene at 80°C for 1 hour yielded Cp2Hf ( OC( CH 2 CHMe 2 ) =CHO) ( 5) , crude 8 0%, 1 H NMR) thick-walled glass reaction isolable as a orange oil. fE*Hf<n 2 -0CHPh)C0 2 A (7). vessel with a teflon needle valve was charged with 0.50 g ( 0 . 9 5 mmo 1 ) Cp ~ Hf ( H ) Ph , (ca. 3.5 atm) temperature. and 1 0 ml was to 1 ue n e , stirred for and 6 . 2 5 mmo 1 C0 24 700. 30.61. room and taken up and recrystallized from petroleum ether to give 0.36 g (66%) IR: at Solvent and residual gas were removed, the orange solid residue was 7. hours of light orange 1956(st), 1600, 1492, 1230, 1120, 1069, 1027, 750, Anal. Calcd. for Found: C, c 28 a 36 Hf0 2 : 57.76; H, 6.30; C, 57.68; H, 6.22; Hf, Hf, 30.68. Solution molecular weight (C H ) Calcd.: 583; Found: 592. 32 6 6 £E*Hf(OC(Ph)=CHO) (8}. The procedure for except 0.33 g of Cp!Hf(H)Ph, 7 was followed 10 ml toluene, and 6.7 mmol <ca. 3 atm) CO were stirred for 3 days at 80°c. workup of 88 the highly soluble orange residue IR: orange 8. 1070, 1046, Found: yielded only 67 mg of 1600, 1580, 1563, 1480, 1320, 1295, 1120' 1025, 870, 757, 692, 680, 583, 475. C, 57. 6 8; H, 6. 2 2; Hf, Anal. 3 0. 61. C, 57.64; H, 6.16; Hf, 30.70. fE.;Hf(OC(CH 2 cH 2 cH 2 cH 2 )C0) (11). A solution of Cp2Hf(CH 2 - CH2cH2cH2> in 10 ml toluene was cooled to -78°C and stirred under 1 atm CO for 2 hours, generating an orange solution of the acyl metallacycle 10. warm slowly to room removed in vacuo. solution was The solution was allowed to temperature 1025' cooled 900' the volatiles were 5 ml of petroleum was distilled and the precipitating crystalline 11 (0.11 g, 40%). 1100, and IR: orange 1640, 1353, 1210, 1157, c, 720. 55.66; H, 6.83; Hf, 31.81. Found: C, 55.38; H, 6.85; Hf, (12). A solution 31.69. 2 ~;zr<OCH(CH CHMe (0.71 mmol> 2 >cH 2 CH 2 > 2 Cp~Zr<H>CH CHMe of 0.34 g 2 in 10 ml toluene was cooled to -78°C and stirred for one half hour to quantitatively form the acyl hydride la ( 1 H NMR > . Excess CO was vacuo and ethylene (2.3 mmol) was admitted. was warmed removed, the slowly and brown ~ to room temperature, removed in The reaction volatiles were 7 ml petroleum ether was distilled onto residue. Cooling to -78°C, filtering, washing once with cold petroleum ether afforded 0.165 and g 89 (46%) of white 12. IR: 58 0 • for C2 7 H4 4 0 Zr : Ana 1 • Ca 1 c d . 19.17. Found: 1363, 1090, 1078, 1010, 952, 846, C, 6 8 . 15 ; H , 9 . 32 ; zr , C, 68.11; H, 9.19; Zr, 19.36. A -7 8°C solution of la derived from 0.30 g (0.60 mmol) Cp2Zr(H)CH 2 CHMe was 2 prepared following the procedure described for 12. Removal of excess CO and slow warming in the presence of 2-butyne (7.1 mmol) yielded upon petroleum ether workup 0.20 g (57%) of IR: 13. 1563, 1486, 1365, 1167, 1120, 1040, 990, 950, 840, 802. Anal. Calcd. for c 69.40; H, 9.24; Zr, 18.17. Found: 1090, 1058, H ozr: 29 46 C, C, 69.16; H, 9.07; Zr, 18.45. fE;Zr(H)OCH 2 cH 2 cHMe 2 <14>. A solution of la derived from 0.350 g (0.78 mmol> cp;Zr(H)CH 2 CHMe was treated with 1 atm 2 H2 at -42°C and warmed vigorous stirring. slowly to room temperature with Removal of solvents and subliming twice the oily residue Cl00°C, 10- 4 torr> afforded 0.235 gm (63%) 14. IR: 1565 986, 857, 765. 9.41. Found: ( v ( Zr-H)), 1510, 1230, 1140, 1105, C, 1026, 66.75; H, C, 66.83; H, 9.73. f£2Zr(C3CtBu)OCH 2 cH CHMe (15). 2 2 A solution of la prepared from 0.30 g (0.57 mmol) was treated with 7.1 mmol !-butylacetylene at -42°C and warmed slowly to room temperature. Removal of volatiles yielded a colorless oil, identified by 90 IR and 1 H NMR as >90% 15. 2090 IR: {v (C=C)), 1378, 1246, 1205, 1138, 1105, 1025, 984, 730. £E*Hf{OCH=CHCH{tBu)) (17). 2 solution A of 0.10 g {0.19 mmol) Cp2Hf(H)CH=CHtBu in 10 ml toluene was stirred at -78°C for 1 hour hydride, 16. Excess under CO 1 was atm CO removed to in generate vacuo, acyl and the bright yellow solution was allowed to warm slowly to room temperature. unstable The solvent was removed, orange oil metallacycle 17. IR: identified 1545 leaving a thermally 1H by ('J (C=C)), at >90% 1236, 1159, NMR 1358, 1098, 1041, 1023, 870, 800. £E~Hf(OCH=CHCH{tBu)C0 ( 0. 40 mmol) {18). A Cp*Hf {H) CH=CHtBu 2 in solution of 0.21 g 5 ml petroleum ether was stirred for 1 hour under 1 atm CO at -78°C, then allowed to warm to room temperature. orange upon warming, overnight. ( 40%) of { v{ C=C)), 7 52 . 30.30. The solution slowly turned deep precipitating bright orange crystals Cooling to -78°C and filtering yielded 0.95 g acylmetallacycle 1358, 1286, 18. 1260, 1110, An a 1 . Ca 1 c d . for C2 8 H4 2 Hf 0 2 : Found: IR: 1610 1040, (v {C-O)), 1024, 968, 1590 838, C , 5 7 . 0 9 ; H, 7 • 19 ; Hf , C, 57.13; H, 7.16; Hf, 30.11. £E~Hf(OCH=CHC{tBu)=CHO) {19) . A thick-walled glass reaction vessel with teflon needle valve was charged with 0.500 g (0.85 mmol) 18, 10 ml toluene, and 700 torr CO and 91 heated to 80°C for 6 hours. light b~own IR: ( C6 D6 ) 15 9 0 ( v ( C=C) ) , Petroleum ether workup of the solution yielded 0.300 g (60%) of off-white 19. 14 6 0, 13 58 , 1311, 1240(st), 1188(st), 1084, 1045, 1022, 883, 763, 587. Anal. C, Found: 14 2 3, 57. 0 9; H, 13 7 8, 7 .19; Hf, 3 0. 3 0. C, 57.17; H, 7.30; Hf, 30.17. Kinetic Measurements. 18 The rearrangement of to spectroscopy, monitoring 19 kinetics were thermal by 1H NMR ratio of runs obeyed first-order kinetics for> 2.5 half lives (see Figure 1). Sealed NMR resonances. All of the followed of the kinetic the !-butyl tubes were thermalized at 80°C(±l), and spectra were taken every 15 minutes. in c 6 o6 > yielded Two runs on rate constants sec- 1 , and one run on 18-g 3. 6) • 18-~ 2 0 ([18-~0 ] = 0.18, 0.36M of 1.51 and 1.50xl0- 4 gave 0.4lxl0- 4 sec-l (kH/k 0 = 92 REFERENCES <1> (a) Parshall, G. "Homogeneous Catalysis", Wiley- Interscience, 1980. Hegedus, L. S. (b) Collman, J.P.; "Principles and Applications of Organotransition Metal Chemistry", University Science Books: (2) Mill Valley, CA, 1980. Schwartz, J.; Labinger, J. A. Angew. Chern. Int. Ed. Engl. 1976, 15, 333. (3) Pine, S. H.; Zahler, R.; Evans, D. A.; Grubbs, R. H. J. Am. Chern. Soc. 1980, 102, 3270. <4> (a) Berry, D. H.; Bercaw, J. E.; Jircitano, A. J.; Mertes, K. B. J. Am. Chern. Soc. 1982, 104, 4712. (b) Manriquez, J. M.; McAlister, D. R.; Sanner, R. D.; Bercaw, J. E. J. Am. Chern. Soc. 1978, 100, 2716. (c) Wolczanski, P. T.; Bercaw, J. E. 1980, 13, 121. Ace. Chern. Res. (d) Barger, P. T.; Bercaw, J. E., submitted to J. Am. Chern. Soc.. (e) Roddick, D. M.; Fryzuk, M. D.; Seidler, P. F.; Hillhouse, G. L.; Bercaw, J. E., manuscript in preparation. (5) Chapter 1, this thesis. (6) (a) Erker, G.; Rosenfeldt, F. Ed. Engl. 1978, 17. 605. Angew. Chern. Int. (b) Ibid., J. Organomet. Chern. 1980, 188, Cl. (c) Moore, E. J., Ph.D. Thesis, California Institute of Technology, 1984, Chapter 3. (7) The structure of 4a,b as drawn, in the sterically 93 preferred form with aldehyde carbon coordinated in the central equatorial position, cannot be differentiated from the alternative structure with the aldehyde oxygen occupying the central coordination site on the basis of spectroscopic data alone. (8) Aldehyde proton chemical shifts typically range from 9. 0 to 9.5 o, Sa while carbonyl carbon 13 C values fall between 190 and 210 pprn. 8 b (a) Dyer, J. R. "Application of Absorption Spectroscopy of Organic Compounds"; Prentice-Hall, Inc., Englewood Cliffs, N.J., 1965. (b) Silverstein, R. M.; Bassler, G. C.; Morrill, T. C. "Spectrometric Identification of Organic Compounds", 4th Ed.; Wiley, N.Y., 1981. (9) Brunner, H.; Wachter, J.; Bernal, I.; Creswick, M. Anqew. Chern. Int. Ed. Engl. 1979, 18, 861. (10) Marsella, J. A.; Curtis, C. J.; Bercaw, J. E.; J. Am. Chern. Soc. 1980, 102, 7244. Caulton, K. G. <11) Manriquez, J. M.; McAlister, D. R.; Sanner, R. D.; Bercaw, J. E. (12) J. Am. Chern. Soc. 1976, ~' 6733. The absence of assignable v(C-0) bands above 1200 cm-l has been noted previously for late metal TI-aldehyde and ketone complexes : Walther, V. D. z. Anorg. Allg. Chern. 1977, 431, 17. (b) Ittel, S. D. (13) J. Organomet. Chern. 1977, 137, 223. Thermolysis of 4a under 3 atm CO results in an approximately equimolar mixture of enolate hydride 94 3 and the zirconium analog to 5 (14) <1H NMR). Cohen, S. A., Ph.D. Thesis, California Institute of Technology, 1982. (15) (a) Tsuji, J. "Organic Synthesis via Metal Carbonyls", Vol. II, Wender, I.~ Pino, P., eds.~ John Wiley & Sons, 1977, p. 595. (b) Walborsky, H. Chem. Soc. 1971, M.~ J. Am. Allen, L. E. ilr 5465. Organometallics 1982, lr 1549. (16) Milstein, D. (17) Recently, the synthesis and structural character~ ization of binuclear bridging formaldehyde and aldehyde complexes of zirconium which exhibit similar chemical reactivity have been reported. (a) Gambarotta, Floriani, C.~ Chiesi-Villa, A.~ J. Am. Chern. Soc. 1983, 105, 1690. Guastini, C. (b) Erker, S.~ G.~ Kropp, K.~ Kruger, C.~ Chiang, A.-P. Chern. Ber. 1982, 115, 2447. (18) Straus, D. A., Ph.D. Thesis, California Institute of Technology, 1983. (19) Erker, G.~ Rosenfeldt, F. J. Organomet. Chern. 1982, 224, 29. (20) Cohen, S. A., manuscript in preparation. <21) A related reaction involving ketone and aldehyde addition to <n 4 -butadiene)zirconocene has recently G.~ Erker, Hunter, W. E. Angew. Chern. Int. Ed. Engl. 1983, 22, 494. Engel, K.~ been reported: Atwood, J. L.~ 95 (22) An alternative mechanism involving hydride migration to· the CO ligand followed by direct coupling, although less likely, cannot be ruled out. (23) Oxycarbenoid character for n2 -acyl ligands in early transition metal and actinide complexes, as 0 1\ M-:C - R c suggested by resonance structure C, has been invoked to explain much of the CO reaction chemistry observed in these systems. 4 b, 25 (24) Wood, C. D.; Schrock, R. R. J. Am. Chern. Soc. 1979, 101, 5421. (25) Manriquez, J. M.; Fagan, P. J.; Marks, T. J.; Day, C. S.; Day, V. W. J. Am. Chern. Soc. 1978, 100, 7112. (26) (a) Substantial steric destabilization of Cp 2 TiCH 2 C<R>CR')CH 2 complexes when R,R'=alkyl has 26 been reported, b and has been attributed to unfavorable ring-( B-substituent) interactions. Such interactions are anticipated to be even more unfavorable in perrnethyl-ring metallocene complexes, such as 20. (b) Straus, D. A.; Grubbs, R. H. Organornetallics 1982, (27) 1, 1658. A number of transition metal complexes with n 4 -<0=C(R)C=CR'R") fun~tionality have been reported. 96 (a) Schrauzer, G. N. Chern. Ber. 1961, i!r 642. (b) Sacerdoti, M.; Bertolasi, V.; Gilli, G. Crysta11ogr. 1980, 36B, 1061. Acta. See also reference 12a. (28) Yasuda, H.; Kajihara, Y.; Mashima, K.; Nagasuna, K.; Lee, K.; Nakamura, A. (29) Marvich, R. H.; Brintzinger, H. H. Chern. Soc. 1971, (30) 1, 388. J. Am. i!r 2046. Brown, T. L.; Dickerhoof, D. W.; Bafus, D. A.; Morgan, G. L. (31) Organometallics 1982, Rev. Sci. Instrum. 1962, llr 491. Hinsberg, W. D., Ph.D. Thesis, California Institute of Technology, 1980. (32) Molecular weight determined by isothermal distillation using the Singer method. Liebigs Ann. Chern. (a) Singer, R. 1930, 478, 246. Ind. Eng. Chern., Anal. Ed. 1941, Justus (b) Clark, E. P. !l, 820. 97 Chapter IV Synthesis and Reactivity of MonoPermethylcyclopentadienyl Hafnium Phosphide Complexes. Structural Characterization of [Cp*HfMe(~-H) (~-PtBu 2 )J 2 2 t and Cp*HfC1 (n -C(O)P Bu ) 2 2 98 INTRODUCTION The complexes chemistry with of hard titanium, donor zirconium, ligand such and as hafnium chloride, alkoxide, and dialkyamide has been studied extensively. 1 In contrast, the chemistry of group IV metals with soft dialkylphosphide donor ligands has not been well developed. In particular, until recently only three examples of Zr(IV) complexes, 2 dialkylphosphide and no examples of Hf(IV) dialkylphosphide complexes had been reported. Phosphide ligands are currently of interest in the field of bimetallic and cluster chemistry 3 because of their pronounced ability to form stable binuclear bridges. This stability is derived in part from the flexible nature of the (~ 2 -PR 2 ) linkages, which can accommodate a range of 3 . meta 1 -meta 1 b on d ~ng an d non b on d'~ng d'~stances. a Although numerous complexes are 5 6 quite rare. ' because of 3 e- d onor known, 4 examples of terminal terminal dialkylamide phosphide complexes are Terminal phosphide ligands are of interest their ability . d s, 6a 1 ~gan to thus function as stabilizing unsaturated complexes while at the same either le- or coordinatively time providing a potential mechanism for generation of a vacant coordination site. 99 L < In light of these considerations,we became interested in exploring the chemistry of hafnium (IV) dialkylphosphide efforts 7 in our laboratory complexes. Prior to this work, to prepare reactive zirconium hydrides via hydrogenolysis of Cp*ZrR (R=alkyl, 3 phosphine were phenyl) in unsuccessful, the giving instead polymeric hydride-containing products. dialkylphosphide ligands, phosphine donor presence of free insoluble, By incorporation of possessing intramolecular functionality, it was hoped that well defined, soluble hydride complexes could be obtained. Accordingly, the mono and and this chapter presents the synthesis of Cp*HfCl ( P t Bu ) 2 2 mono-phosphide alkyl derivatives 1 alkylation complexes t Cp*HfC1 <P Bu ( 2) as well as and aryl derivatives. bis-phosphide of of 1, have or been prepared metathesis of > ( 1) number of 2 a by Cp*Hf 2 Hydrocarbon either alkyl direct or aryl chlorides with LiPtBu • The choice of PtBu as ligand for 2 2 the study of hafnium phosphide complexes was primarily for steric control. 8 ' 3 a Specifically, it was hoped that 100 sufficient ligand bulk would favor terminal coordination, as well as stabilize desired hydride complexes with respect to oligimerization. Hydrogenolysis of hafnium phosphides proved to be a general reaction for cleavage of both Hf-C and Hf-P bonds, yielding insoluble hydridophosphide dimers or, in the case of 1, products formed Cp*HfC1 H. The product 2 Cp*HfMe (PtBu ) (6) and 2 2 ( 8), has derived from the been structurally characterized. from initially reaction of Additionally, Cp*HfC1 <PtBu > is found to react readily with CO to give 2 2 the novel, structurally characterized Cp*HfC1 <n 2 -C(O)PtBu > (13). 2 2 insertion product 101 RESULTS AND DISCUSSION (1) Synthesis of Cp2HfC1 (PtBu > (1) 2 2 and Cp2HfCl(PtBu l 2 2 ( 2) • Treatment of Cp*HfC1 with one equivalent LiPtBu or 2 3 excess LiPtBu in diethyl ether afforded deeply-colored 2 t t . phosphide complexes Cp*HfC1 <P Bu > (1) and Cp*HfCl(P Bu > 2 2 2 2 (2) respectively, in good yield. moisture sensitive, to air. Both 1 and 2 are highly and lose HPtBu 2 rapidly upon exposure Solution molecular weight lL~ Cp*HfC1 xs. 1 (1) 3 Li~ 2 found: 512) as well as 1 H and 31 P NMR analytical data monomeric, terminal stoichiometry. single low support field within the resonances data range are formulation of 1 complex the indicated at of 209.9 comparative limited, reported phosphide complexes and as a P { 1 H } NMR spectra of 1 and 2 exhibit Although respectively. spectroscopic phosphide 31 The the (see Table I) for these trigonal and 261.3 ppm, structural and 31 P fall values planar (170-320 ppm>, 6 and appear terminal indicative 102 of a TI-donor, 3-electron coordination mode Both 1 and magnetically equivalent !-butyl groups in the phosphide 18H, ligands o 1.45.; 12.6 Hz). 3 of JPH The 1 and 2. = 12.2 Hz. equivalence 2: of for 1 2 exhibit H NMR o 1.59.; 36H, !-butyl the groups 3 in ( 1: JPH = 1 is consistent with a static structure A, where the !-butyl tsu * ~ / Hf''''CI \ Cl I tsu 8 A groups are related observation of a by a mirror single resonance plane; for however, the the diastereotopic 1-butyl groups in 2 and in alkyl derivatives of 1 (Table I) requires equilibration via suggests that about complexes is rapid broadening of the rotation on the 1-butyl a NMR fluxional the Hf-P process, bond timescale. resonances for 1 and in these Only slight and 2 was observed down to -94°C, placing an upper limit of - 10 kcal on 6 G~ for site exchange. 9 103 (2) Synthesis of Cp!-HfRR'(PtBu 2 Complexes > (R,R'=Cl, alkyl or aryl). Preparative routes to a number of alkyl der iva ti ves of 1 and 2 have been examined. prepare derivatives methyl and phenyl of and aryl At tempts 1 by to direct methathesis of Cp*HfC1 cPtBu > with MeLi, MeMgBr, or PhLi 2 2 at -78°C were not successful. one However, reaction of 1 with equivalent LiCH CMe in toluene or KCH Ph in ether 3 2 2 1 yielded >90% pure < H NMR) Cp*HfCl(CH CMe )(PtBu > (3) and 2 3 2 ( 4) analytically pure Cp*HfCl ( CH Ph) ( P tBu ) as highly 2 2 colored, crystalline solids (equation 2). The phosphides Cp*HfMe CPtBu > (5) and Cp*HfCl(Ph)(PtBu > (6) may be 2 2 2 ( 2) readily obtained from the reaction of the corresponding chlorides Cp*HfMe Cl and Cp*HfPhC1 , prepared by metathesis 2 2 of Cp*HfC1 with MeMgBr or PhLi (see experimental section), 3 with one equivalent LiPtBu in diethyl ether (equations 3 2 and 4) . 104 . t L1.P Bu Cp*H_fMe Cl 2 . t L1.P Bu Cp*HfPhCl t Cp*HfMe (P Bu > 2 2 2 ( 3) 5 2 Cp*HfCl(Ph)(PtBu 2 > (4) of the 6 Efforts sterically to prepare crowded derivatives alkyl bis-phosphide 2 were unsuccessful. Neither treatment of 2 with MeLi or MeMgBr, nor reaction of Cp*HfMeC1 2 with excess LiPtBu yielded 2 any identifiable products. All of thermally quite the stable soluble phosphide and, in like derivatives the aromatic, NMR ppm are comparable dichloride ethereal, solvents. (220-225) parent to prepared and are 1, are hydrocarbon resonances for 3-6 observed for 1, that indicating similar terminal n-donor phosphide coordination. ( 3) t Reaction of Cp2HfMe <P Bu > (5) with Hydrogen 2 2 A reaction which has been used with some success for preparation of various cyclopentadienyl hydrides of Zr?,lO and HflO,ll is the hydrogenolysis of methyl complex, as shown in equation 5. the corresponding Therefore, in an /CH 3 Cp' M 2""-.,. ( 5) CH Cp' 3 = C5 Hn Me 4 -n R (R = alkyl, H) 105 the dimethyl 5 with H 2 was examined. reaction Treatment of of benzene solutions of 5 with 2-3 atm H at 25°C induced clean loss 2 1 of methane < H NMR) over the course of several days to form an insoluble, crystalline yellow solid. Acidolysis of the isolated analysis solid with HCl and Toepler of the volatiles yielded 1.63 equivalents of a 1:1 mixture of H 2 and CH 4 which, together with elemental analysis, confirmed a product stoichiometry Cp*Hf(H)Me(PtBu 2 > <7>. The t [Cp*Hf(H)Me(P Bu )] 2 2 7 5 formulation crystal of ( 6) 7 structure as a dimer <vide has been infra). verified Mass by its spectroscopic analysis of the methane produced in the reaction of 5 with o2 indicated CH o, a 4-centered hydrogenolysis mechanism as shown in Scheme 1. Analogous >95% 3 consistent with 106 Scheme I 4-center mechanisms have been proposed by Schwartz for the H -promoted 2 reductive elimination Cp Zr(H)CH CH(CH > cH , 12 2 2 2 4 2 exchange reactions complexes. of of alkane from H-D and by Andersen for the thorium and uranium trimethylsilyl 13 The confirmed presence by of hydride infrared 7 6 0 em -l ; v <Hf- D ) ligand in 7 has been = 1510, spectroscopy (V(Hf-H) 5 4 8 em -l ) . Comparison of these = 1 09 0 , values with values reported for a number of zirconium and hafnium hydrides (Table II) suggests no clear assignment of hydride ligation mode. a terminal hydride mode, low energy 7 60 em Cp MH complexes. 15 3 a -1 The high energy stretch is low for 14 stretch by its have only been reported for Though IR data are most consistent with terminal hydride complex, indicated while comparable values to the the aggregate nature of 7, insolubility, is insoluble bridging hydride oligomers. more suggestive as of TABLE II. Infrared Data for Selected Zr and Hf Hydride Ccrrplexes. -1 v(M-~) v (M-H+-) an Cantx>und [Cp*HfH(CH 3 )P~u2 J 2 (7) 1510,760 [Cp*HfH(Cl)P~u ] 1516,770 22 (9) -1 an Ref. ep zrH 3 1609, 752 15 ep H£H 3 1670, 764 15 [CpZrH2 ]x 1520 1300 (br) 16 [MeCpZrH ] 2 2 [ep zr(H)Cl]x 2 * ep2ZrH2 1565 1330 (br) 23 1565 1390 (br) 16 1555 1390 (br) 17 1590 1390 (br) 11 1628 1350-1500 (br) 7 0 Cp~H£H 2 4 [Cp*Zr(BH )H(~-H)] 1--' z [Cp*HfClH ] 2 2 Cp;Hf(H)CH2CHMe 2 1575 1320 (br) 18 1636 1320 (br} 11 Cp;Hf (H) CH=QI (~u) 1620 1320 (br) 11 cis-[Cp;H£H] 2 (~-GCH=CHO) 1655 1320 (br) 11 -J 108 The structure ambidentate readily nature adopt of 7 of the either is further phosphine terminal or complicated ligands, bridging by the which may geometries. Taken together, at least three possible dimeric structures may be envisioned. In order to address these problems, as well as assess the relative bonding preferences of H and PR (bridging vs. terminal>, the structure of 7 has been 2 determined by x-ray diffraction. c D 109 (4) {Cp*HfMe(}l-H) (}..1-PtBu ll 2 2 Structural Determination of (7) • The molecular structure t JCp*HfMe(~-H)(~-P Bu >J (7) 2 2 is presented in Figure 1, a stereoview in Figure 2, and a skeletal view of the immediate ligation about hafnium with relevant bond distances and bond angles is given in of two Figure 3. The molecular structure of 7 consists <n 5 -c Me >HfMe(H)(PtBu > units b.ridged by two 3-center, 5 5 2 electron Hf-P-Hf' bonds 0 = (Hf-P 2.805(2) A, A; P-Hf-P' = 109.2(1) 0 , Hf-P-Hf' = 70.8(1) 0 ). overall molecular crystallographic ring groups. 2.537(9) values of of The 2.589(9) to somewhat center of 7 is inversion constrained located The by between a the resulting in a trans orientation of methyl hafnium atoms, and symmetry = Hf-P' 2.807(2) 4 Hf-C(ring) 0 A, 0 closely 2.55 A in longer than the average length, 2.25(9) 2 2 0 A, is (vide similar to range the from average Cp*Hf(H><n 3 -cH CHCH >19 2 2 2.54, Cp*HfC1 <n 2 -C(O)PtBu > 2 2 distances value infra). of The 2.47 0 A Hf-C(a) and for bond intermediate between the reported 0 20 0 values of 2.23(1), 2.24(1) A in cp HfMe , 2.30(1) A in 2 2 21 5 22 [Cp HfMelf~ -o> and 2.33(1) A in <n -c 9 H7 >2 HfMe 2 . The ligation mode of the hydride ligands in 7 is of primary interest. Although limitations of the data (see Experimental Section> prevented a precise determination of the hydride position, examination of difference Fourier maps of the plane perpendicular to the Hf P 2 2 plane revealed 110 Figure 1. Structure of [Cp*HfMe(~-H) (~-P t Bu )J (7). 2 2 111 Figure 2. Stereo view of [Cp*HfMe(~-H) (~-P t Bu )J (7). 2 2 112 - .... 0::: Figure 3. Skeletal view of [Cp*HfMe(~-H) (~-P 0 t Bu )J (7), 2 2 with selected bond distances (A) and angles ( 0 ) . 113 electron density attributable to a bridging hydride ligand; subsequent least-squares refinement of hydride coordinates gave values of Hf-H = 94(5) 0 , Hf-H-Hf' 0 = 2.12(13) and A, Hf-H' = 2.33(13) = 86(5) 0 • H-Hf-H' The 0 A, observed asymmetry of the Hf H unit is consistent with structural 2 2 data for the related complex [<c a Me> ZrHt(l-1-Hb>] 2 5 4 (Zr-Ht 2 = 1.78(2) A, Zr-Hb = 1.94(2) A, Zr-Hb = 2.05(3) A>. 23 mean Hf-H bond length in than values (2.069(7), of 7 hafnium for A> 24 2.120(8) 0 2. 2 A is The somewhat greater complexes and Hf(BH > 4 4 significantly longer than the terminal Hf-H bond length of 1.85(7) A for Cp2Hf<H><n 3 -cH 2 cacH 2 >. 26 , 27 The crystallographic data for 7 are in accord with the quadruply-bridged dimeric structure E. Additionally, it is evident from this structure that phosphide ligands do not provide a suitable ligand environment for stabilization of monomeric hafnium hydride complexes. In particular, 0 comparison reported of Hf-P terminal (2.488 bond lengths n-donor Hf-P (ave. 2.806 values for A) 2.504 A> 6 b indicates Hf-P bonds occur to 2.475, that considerable lengthening of the upon . 29 b r~'d g~ng. As a result, significant steric interactions between the bulky phosphide and groups 7 cp Hf(PEt > 2 2 2 (2.533, and in the permethyl rings of incurred, 30 and dimer formation is not prevented. no ~-butyl 7 are 114 2 2 (X=CH 3 ,Cl). Reactivity of [Cp*HfX(~-H)(y-PtBu ll (5) The chemistry of [Cp*Hf(H)Me(PtBu J 2 Unlike disappointing. 2 (7 oligomeric is or <cp 2 Zr(H)Cl>x' which are sparingly soluble yet reactive in refluxing benzene, 7 decomposes over the course of several At room temperature 7 is completely unreactive towards H2 , CO, or allene, and decomposes in the presence of excess reagent upon warming to 80°C. [Cp*HfMe (~ -H > (~ -P tBu2 > ] 2 does, however, excess cleanly ethylene at ethylene-inserted 25°C to react slowly with give <1 H NMR) product, the ( 8) • Attempts to form (7) 7 8 soluble, more reactive derivatives of 7 by treatment of the formally 16 electron complex with donor PMe 3 or NMe 3 were not successful. ligands such as Another approach to the problem of enhancing hydride reactivity is to increase the thermal stability of 7 by reactive CH 3 group with Cl. replacing the potentially Treatment of benzene solutions of Cp*HfCl(CH Ph)(PtBu > (4) or Cp*HfCl(CH CMe )(PtBu > (3) 2 2 2 2 3 with H2 readily afforded insoluble yellow 9, the hydridochloride virtue of dimer character is tic IR formulat~d [ Cp*HfCl(~-H) <~-PtBu 2 )] <v ( Hf-H) = 1516, as by 2 770 em -l 115 = 1085, (Hf-D) analogy to 7. 540 cm-l) and Unfortunately, 9 - analytical data, proved no more and by thermally t [Cp*HfCl (1-!-H) (1-!-P Bu )] 2 2 ( 8) 9 3, R = CH CMe 2 3 4, R = CH Ph 2 stable than 7 and even less reactive, failing to insert c 2 H4 after prolonged exposure at 25°C. ( 6) Reaction of Cp*HfC1 ( P tBu ) and Cp*HfCl ( P tBu l_ 2 2 2 2 ( 2) with H2...:.. During the course of investigating the H reactions 2 of alkyl phosphide complexes, phosphide genolysis. bonds are also it was readily Reaction of Cp*HfCl(PtBu found that hafni urn- susceptible > 2 2 to hydro- (2) with 2-3 atm H 2 is rapid, quantitatively yielding 9 plus one equivalent of free phosphine, HP t Bu 2 • Qualitatively, for the series Cp*HfCl(PtBu ) 2 2 ( 9) 2 9 Cp*HfCl(R) (PtBu 2 > (R = PtBu 2 (2), CH 2 CMe 3 (3), CH 2 Ph (4)), the observed relative rate of hydrogenolysis 31 (equations 8 and 9) is 2 > 3 >> 4. energies for Comparison of mean bond dissociation the homleptic alkyls ZrR 4 (R = CH 2 CMe 3 , D = 116 54 kcal mol -1 ; R that of the ease related to = CH 2 Ph, hydrogenolysis 1 igand bond kcal mol -1 ) 32 suggests = 60 D of 2, 3 and 4 may be strengths, Hf-CH 2 CMe 3 > Hf-PtBu 2 (complex 2) for this series. The parent phosphide reacts slowly under weeks to give 3 complex, atm H over 2 disproportionation (Cp*HfH 2 cl>x, 33 plus Cp*HfC1 (P tBu ) 2 2 1 Cp*HfC1 ( P tBu ) the course of products ( 1), 2 2 several Cp*HfC1 and 3 -40% decomposition (equation 10). t -HP Bu [Cp*HfC1 H] 2 10 2 (10) In the presence of one or more equivalents of PMe , the 3 hydrogenolysis of 1 is complete within minutes at 25°C to give an uncharacterized intermediacy of mixture monohydride 10 in of products. equation 10 has The been confirmed by trapping with excess ethylene to cleanly give the inserted excess PMe , 3 is product, the reaction of rapid, quantitatively, In Cp*HfC1 2 ( Et > . 1 with 3 the presence a tm H 2 and excess (11) producing isolable in 71% of yield as an off-white, analytically pure crystalline solid (equation 11). Cp*HfC1 (PtBu ) 2 2 + + (11) 1 Cp*HfC1 (Et) (PMe ) 2 3 11 + 117 Whereas the origin of the phosphine promoter effect in reactions of 1 with H2 is not fully understood, should be noted that no significant effect by added PMe the rate of hydrogenolysis Cp*HfMeC1 2 is observed. of the alkyl In light of this, ligand it 3 on in the phosphine effect on hydrogenolysis may be attributed to the loss of the n-donor interaction of the terminal phosphide with the metal center: coordination of phosphine to 1 in a rapid albeit unfavorable electron rich, phosphide lone 16 equilibrium 34 electron pair to form complex, interaction may with a relatively weaken the the hafnium, facilitating cleavage of the remaining sigma bond (Scheme 2). Moreover, localization of the lone pair on phosphorus 1l Scheme 2 ~Products would be expected to enhance the rate of a heterolytic, four-center mechanism involving a polar intermediate such as: 118 This rationalization is consistent with the observed rapid hydrogenolysis of the bis-phosphide, 2, which is also formally a 16-electron complex. (7) Synthesis and Structure of Cp*HfC1 (n 2-C(O)P t Bu ) (12). 2 2 The results of hafnium-phosphide hafnium-alkyl the bonds bonds. preceding to be section comparable have shown in energy to In light of the proclivity of group 2 give stable n - IV alkyl complexes toward CO insertion to acyl products, it was anticipated that hafnium phosphide reactivity. Indeed, complexes should exhibit similar Cp*HfC1 (PtBu ) 2 2 (1) reacts with 2 atm minutes to give quantitatively CO at ( 1 H NMR) the carboxyphos2 t phide insertion product Cp*HfC1 2 (n -C(O)P Bu 2 ) tion 12). 25°C within (12) (equa- 119 co 2 Cp*HfC1 (n -C(O)PtBu ) 2 (12) 2 12 1 Carboxyphosphide 12, isolated as bright a yellow analytically pure crystalline solid (73%), has been fully characterized spectroscopically. The infrared spectrum of 12 exhibits a strong v(CO) band at 1350 cm-l which shifts to 1320 cm-l upon isotopic substitution with 13co. v(CO) values reported 2 and actinide n -acyl This value is markedly lower than for related transition 2 n -carboxyamide metal complexes and (see Table III), and is more comparable to values reported for exo and endo 1427, 1417 of Cp* ZrH ( n 2 -c <0 >CHPMe > <v <c-o> = 2 3 1 41 cm- , respectively> in which significant isomers multiple bonding between atom observed. The is the C(acyl) and adjacent carbon 13 c{ 1 H} complex, Cp*HfC1 <n 2 - 13 c<O>PtBu >, 2 2 3. 0 3 ( 1 JPC ppm carbon atom. = 101 Hz), spectrum of the labeled displays doublet attributable to a the at carbonyl This observed shift is at considerably higher field than characteristic lowfield, "carbene-like" acyl and carboxyamide values (Table III), and suggests a significant TI-interaction phosphorus of lone the pair. carbonyl carbon Together, atom these with data the clearly indicate a substantial contribution of canonical form F to the overall valence bonding description. TABLE IIL a 2 IR and 13c{~} NMR Data of M-(n -c(O)R) Conplexes. CanfX:>und IR (an-l) 2 ep* ThCl(n -c(O)CH2CMe 3 ) 2 1469 ~2 ZrMe(n 2 -c(O)Me) 1545 2 . !-cp zr(P-tolyl) (n -C(O) (P-tolyl) 2 2 ~-cp zr(P-tolyl) (n -c(O) (P-tolyl) 2 2 ep ZrCl(n -c(O)CH CMe 3) 2 2 2 Cp* ThCl(n -c(O)NEt 2) 2 2 ep U(n -c(O)CHPMePh 2 ) 3 2 !-cp* ZrH(n -C(O)CHPMe 3) 2 2 ~-cp* ZrH(n -c(O)CHPMe ) 3 2 Cp*HfC1 2 (n2 -c(O)P~u2 ) (12) Acyl 13 c Chemical Shift (pm) 360.2 35 36 1480 300 37 1505 301 37 1550 318.7 38 1516 248.5 39 ....... tv 40 1440 1427 250.3 41 1417 247.1 41 1350 3.03 a .!. refers to the iSOI'lEric form where the acyl oxygen occupies the lateral equatorial site. ~ refers . Ref. to the centrally located acyl oxygen isc::~rer. 0 121 .o 0 0 /\ ;·~ _I\ M--C~+ PR 2 M+-:C" M--C"' PR 2 PR 2 H G F 1 H NMR spectrum of The room temperature 9 0 MHz exhibits a = single 14.2 inequivalent ~-butyl resonance indicating Hz> , (vide methyl infra) that phosphide at 1.31 Qpm exchange ~-butyl 12 of the groups and hence rotation about the C(acyl>-P bond is rapid on the NMR timescale. Upon cooling, the coalesces at -58°C. ~-butyl doublet broadens and The slow exchange limit for 12 was not resolved at 90 MHz; however, 500 MHz 1 H NMR of 12 at -93°C 3 displays a pair of doublets c JPH inequivalent ~-butyl groups = 10.7, 12.3 Hz) for the with 6v = 143 ± 2 Hz, corresponding to a frequency separation of 25.7 ± 0.4 Hz at 90 MHz observation frequency. From these values, (-58°C> for rotation about the C-P bond is calculated 42 to be 10.7 ± 0.1 kcal mol -1 . This observed rotational barrier is somewhat lower than barriers found for transition metal n1 -carboxyamides ( 14-24 kcal mol-l), 43 and is far lower than the rotational barrier estimated for Cp* 2 ThCl<n 2 - 122 C(Q)NMe 2 kcal mol-l). 39 <>23 .> These values reflect the extent of multiple C-E (E=N,P) bonding, and are consistent trends with observed for amide s organic . and acy 1 . 44 p h osp h 1.nes. Cry~tal Structure of Cp*HfC1 2 <n 2 -c<O>PtBu 2 > (12). (8) Complex 12 metal-ligated represents the carboxyphosphide first example moiety. In of a order to substantiate the unusual coordination and ligand geometries suggested by the preceding spectrocopic data, the structure of 12 has been determined by X-ray diffraction. The molecular structure of Cp*HfC1 <n 2 -c<O>PtBu > is presented 2 2 in Figure 4, a stereo view in Figure 5, and a skeletal view of the immediate ligation about the hafnium and phosphorus atoms with relevant bond distances and angles is given in Figure 6. The hafnium coordination geometry may be described as a distorted tetrahedron, if n 5 -c 5 <cH > 3 5 and n 5 -C(O)PtBu 2 ligands are considered to each occupy a single geometrical site. The four ring centroid-Hf-X (X = Cl, Y; where Y is defined as the midpoint of the C-O vector) angles vary from 109.7(1) 0 to 116.1(1) 0 , and the remaining three angles are Cl(l)-Hf-Cl(2) = 98.0(1) 0 , Cl(2)-Hf-Y = 112.9 0 . and 2. 3 8 3 < 2) reported and for 0 A are Cl(l)-Hf-Y 101.1 0 , and The Hf-Cl bond lengths of 2. 39 3 ( 2) somewhat shorter (CH 2 >3 <c 5 H4 >2 HfC1 2 [<SiMe 3 >3 N] 3 HfCl = (2.436(5) than (2.417)3), A>. 46 Hf-Cl values 2.429(2) Further, A> 45 Hf-C(ring) 123 124 125 0 with selected bond distances (A) and angles ( 0 ) . 126 0 values (2.459(6)-2.471(6) relative (2.54, for to average 2.55 ~> 26 and normal [Cp 2 HfMel o 2 ring values complexes the of known 47 dependence and observations are of ligands bond as lengths three, [(CH > cc a > ]HfC1 2 3 5 4 2 2 of on 46 and the 12 are Since the effective ionic respectively. of Hf(IV) A> 22 (2.50(1) These A), and Defining the effective coordination numbers eight and seven, radius Cp HfMe 2 2 cyclopentadienyl coordination Cp* 2 Hf<H><n 3 -ca cHCH > 2 2 for A>. 21 coordination number. number significantly contracted [Cp*HfMe(lJ-H) (~ -PtBu l (2.57 2 2 (2.513(5) consistent with are A) (8 coord.> is 0.83 A and that of Hf(IV) 0 0 (7 coord.) is 0.76 A, an approximately 0.07 A difference in Hf-Cl and Hf-C(ring> bond lengths is anticipated, in reasonable agreement with the observed trend. The ligand coordination in 12 is geometry similar to of the that carboxyphosphide reported dihaptoacyl and ~ 2 -carboxyamide structures. 0 for other The C-O bond • distance for 12 , 1. 284 ( 6) A, 1s somewhat longer than values reported for simple n 2 -acyl Cp 2 ZrMe<n 2 -cco>Me) (1.211(8) A> 36 and cp 2 ThCl<n 2 -cco>cH 2 CMe 3 > <1.18(3) and similar is to c-o bond distances reported A>, 35 for 41 2 ZrH<n -c<O>CHPMe > (1.303(3) A> and 2 3 ° ave.>. Cp* ucn 2 -C(O)NMe > 39 <1.275 A The Hf-0 distance, 2 2 2 .£-Cp* 2.117(4) 0 A, 0 1.94-2.25 A, is 48 comparable to reported Hf-0 0 values, and is 0.008 A shorter than the Hf-C(acyl) bond, reflecting the high oxophillicity of Hf(!V). 127 Comparison of the carboxyphosphide moiety in 12 with reported acylphosphine structures C(acyl>-P bond distances C(alkyl>-P bond lengths, is revealing. Whereas Fe 2 cco> 5 [Ph PCCCR>=CR'] 2 o 49 t <?.~ t o s o R (1.918(6) A), ( Bu> PCCP( Bu ) (1.88 A), and MeCPMe 2 2 2 51 ( 1. 87 ( 3 > A) are essentially identical to the remaining 0 1.782(5) A, is 0.09 in the A shorter, C(acyl>-P implying bond in 12, significant P=C This observation is in accord with the 10.7 kcal rotational barrier about the P-C(acyl> bond, and is consistent with a contribution of hybrid structure F to the composite valence bonding description of 12. Overall, the n2 -carboxy- 0 phosphide ligand is planar to within 0.06 A, and may best be described ligand. as a valence-delocalized three electron 128 Conclusion Although the initial goal of preparing reactive hydridophosphide complexes of hafnium was not realized, the results described in this chapter are enlightening. Unlike the related dialkylamide and alkoxide complexes Cp*HfMe x 2 52 (X= niPr , NMe , OtBu, OiPh>, which react with H only 2 2 2 at elevated temperatures to form uncharacterized product mixtures, the phosphide complexes studied react with H2 at room temperature to give well defined hydride products in The origin of the enhanced reactivity is several cases. uncertain·. weaker One possible explanation is that the presumably interaction of the phosphide lone pair with the hafnium metal center relative to strong amide and alkoxy 3 electron donor ligands affords a level of valence unsaturation more conducive to a 4-center H2 interaction. Alternatively, the greater polarizability of soft PR 2 ligands compared to hard, first row heteroatom ligands may better stabilize a four-center hydrogenolysis transition state with dipolar character: §~ §~ M·---C~ I ,, M-C~ + " H-H M I ~ !~f ! 8+ H----H ~ ~ ~ c~ IH + HI' 129 The susceptibility of Hf-P and CO insertion, Although bonds to hydrogenolysis though unanticipated, is not surprising. thermochemical data for M-PR 2 bond dissociation energies is not available, D(Hf-PR > is anticipated to be 2 substantially less than the 88 kcal mol-l value reported >. 32 Consistent with this ordering, analogous 2 hydrogenolysis and carboxylation reactivity for the related for .D<Hf-NEt amides Cp*HfCl?NR 2 (R = i-Pr, Me, SiMe 3 > is not observed. 52 Comparison of Hf-ptau 2 and Hf-R (R = alkyl) rates of hydrogenolysis for the complexes Cp*HfCl(X)(ptau 2 > CX = ptau 2 , CH 2 CMe 3 , CH 2 Ph), while not a direct measure of relative bond enthalpies, similarly suggests that Hf-PR 2 bonds are relatively weak. The results of this chapter have some bearing on the proposed use of PR 2 as a stabilizing ligand in bimetallic and cluster metal chemistry, systems. Our particularly for findings on metal early transition PR reactivity 2 suggest that, contrary to what has been proposed, 3 dialkylphosphide ligands bridging ligands. may not always function as innocent NMR~ DATA TABLE I. Compound Assignment t Cp*HfC1 P su (1) 2 2 C5(C!!3)5 Nucleus lH NMR P(C(C!!3)3)2 ~(C(CH )3)2 3lp{lH} NMR C5(C!!3)5 lH NMR 3 Cp*HfCl(PtBu J 2 2 (~) (~(C(CH )3)2)2 3lp{lH} NMR Cp*HfCl(CH C(CH ) )PtBu (l) 2 3 3 2 C5(C!!3)5 lH NMR Cp*HfCl(CH Ph)PtBu (4) 2 2 JPH 0.3 1. 45 d JPH 12.2 JPH 12.6 JPH 12.9 JHH 13.5 JPH 13.1 209.9 2.19 s 261.3 2.05 s P(C(C!!3)3)2 1.45 d CH C(C!! ) 2 3 3 1. 37 s C!! 2 C(CH 3 )3 -0.20 ~(C(CH3)3)2 C5(C!!3)5 Jlp{lH} NMR 1 u NMR d~ CH2C6!!5 C!!2C6H5 1. 74 dd ~(C(CHJ)3)2 w 0 2.00 s 6.8-7.4 m Jlp{lH} NMR 1--' 213.6 1.30 d P(C(C!!3)3)2 coupling 2.10 d 1.59 d (P(C(C!!3)3)2)2 3 Chemical Shift 222.2 2 JHH=lJ. 2 , ) JPH=J TABLE I (cont'd) t Cp*HfMe 2 P Bu 2 (5) Cp*HfCl(Ph)PtBu 2 C5(C!!_3)5 (6) 2 (8) 1 u NMR Chemical Shift 1.98 s P(C(C!!_3)3)2 1.41 d JPH = 12.9 Hf(C!!_ ) 3 2 0.26 d JPH = 2.5 ~(C(CH3)3)2 31 P{ 1 H} NMR C5(C!!3)5 1 u NMR 202.5 2.07 s P(C(C!!_3)3)2 1. 38 d c6!!s 8.13 m c6!!5 7.20 m ~(C(CH3)3)2 Cp*HfMe(Et)PtBu Nucleus Assignment Compound C5(C!!_3)5 31 P{ 1H} NMR 1 u NMR JPH = 13.2 t-' w t-' 216.2 1.97 s P(C(C!!_3)3)2 1. 35 d Hf(C!!_ ) 3 Hf (C!!_ cu ) 2 3 Hf (CH C!!_ ) 2 3 0.25 s,br JPH = 12.6 0.39 q JHH = 8.1 2.03 t JHH = 8.1 TABLE I (cor.t 'd) Compound Assignment Cp*HfC1 (Et) (PMe ) (11) 3 2 C5(C!!3)5 2 Cp*HfC1 ( n -c (0) Ptsu ) 2 2 (12) Nucleus 1 u NMR Coupling 2.00 s P(C!!3)3 0.97 d JPH = 5.0 Hf(C!! cu ) 2 2 0.75 q JHH = 7.5 Hf (CH C!! ) 2 3 1.80 t JHH = 7. 5 JPH = 13.5 C5(C!!3)5 1 u NMR 2.01 8 1.30 d P(C(C!!3)3)2 2 13 Cp*HfC1 <n - C(O)PtBu ) 2 2 Chemical Shift l3C{ lH} NMR 11.77 8 C (CH 3 )5 -5 122.45 8 P(C(£H3)3)2 31.10 d JPH = 7.9 P(£(CH3)3)2 13 Hf £(0) 38.11 d JPH = 11.9 3.03 d JPH = lOl. S 92.6 JPH c5 (£H3) 5 ~(C(CH3)3)2 3lp{ lH} NMR d = 101. 5 --~ 1 u (90 MHz), 13 c (22.5 MHz), and 31 P (36.3 MHz) NMR spectra taken in benzene-~ at ambient temperatures. 1 u and 13 c chemical shifts are reported in 6 relative to internal TMS or residual protons or carbons in solvent. 3lp chemical shifts are reported in 6 relative to 85% H Po external standard. Coupling constants are reported in Hz. 3 4 ......, w N 133 Experimental Section General performed using techniques. either Solvents first · from LiAlH 4 or "titanocene". 53 methods. 54 All Considerations. glove were box purified was 2 Trimethylphosphine purified were by vermiculite 55 and activated 4 high were vacuum line by vacuum ketyl and then prepared by literature (Strem) vacuum, and distilled prior to use. (Matheson) or benzophenone LiPtBu manipulations was transfer stored from under Hydrogen and Deuterium passage MnO over Amolecular sieves. on Ethylene and carbon monoxide were used directly from the cylinder. Elemental Dornis analyses and were determined Kolbe, Galbraith spectra were by and Alfred Bernhardt, C.I.T. Analytical Laboratories. 1 H NMR recorded using Varian JEOL FX90Q, and BRUKER 500 MHz spectrometers. EM-390, 13 c and 31 P NMR spectra were obtained using a JEOL FX90Q spectrometer. Infrared spectra were measured on a Beckman 4240 spectrometer as nujol mulls, and are reported in cm- 1 . Several reactions were conducted in sealed NMR tubes and monitored by 1 H NMR spectroscopy. the reaction of A typical example is Cp*HfCl(CH Ph)(PtBu > 2 2 (4) with H 2 4 (20 mg, 0.04 mmol) was transferred to an NMR tube sealed to a ground-glass joint and fitted with a teflon needle valve adapter. Benzene-g 6 (0.3 ml) was distilled into the tube 134 at 77 K, 730 torr H was admitted, and the tube was sealed 2 with a torch. Procedures. Cp*HfC1 <PtBu > (1). Cp*HfC1 3 (4.04 g, 2 2 9.6 mmol) and LiPtBu (1.48 g, 9.7 mmol) were placed in a 2 flask, and ca. 40 ml of diethyl ether was distilled in at -78°C. deep Initially pale yellow, the reaction mixture turned green stirring at upon warming to 25°C for hours, 12 room temperature. the diethyl replaced with 30 m1 of petroleum ether, filtered and the precipitate ether. Concentration was and After ether was the solution was washed with crystallization petroleum at -78°C, followed by sublimation (90°C, 10- 4 torr) yielded 2.84 g of deep green 1 ( 5 6% ) • Calcd. for c 13. 4 0. a 18 33 Found: I R : 13 6 0 , 116 3 ( e t ) , 1 0 2 0 , 7 9 8 . cl HfP: 2 C, C, H, 4 0. 3 8; Ana 1 • 40.81; H, 6.28; P, 5.85; Cl, 7 .1 0; P, 5 • 6 5; Cl, 13. 3 8. Solution molecular weight <c 6 o > calcd.: 529; found: 512. 6 56 Cp*HfCl(PtBu l (2). Cp*HfC1 (0.50 g, 1.19 mmo1) 3 2 2 LiPtBu (0.452 g, 2.97 mmol) were placed in a flask, 2 and 20 ml The of diethyl ether was distilled in at -78°C. and reaction mixture was warmed to room temperature and stirred for 12 hours. petroleum ether The volatiles was 1166(st), 1023, 813. removed in. The distilled f i 1 tered and concentrated to afforded 0.485 g (64%) were ca. 7 ml; in vacuo and solution cooling of dark olive green 2. was to -7 8°C IR: 1361, 135 48.83; H, 8.04; Cl, 5.54; P, 9.68. Found: C, 48.76; H, 7.93; Cl, 5.48; P, 9.64. Cp*HfCl(CH CMe ><PtBu > (3). 2 3 2 distilled onto a mixture 30 ml of diethyl ether was t of Cp*HfC1 <P Bu 2 > (0.500 g, 2 0.95 mmol) and LiCH CMe (0.077 g, 0.99 mmol) at -78°C, and 2 3 the reaction mixture was warmed slowly to room temperature with stirring. After 12 hours, the diethyl removed and petroleum ether was distilled in. ether was Filtration, washing and crystallization at -78°C yielded only 0.109 g <19%) of highly soluble maroon solid, >90% 3, by 1 H NMR. IR: 1360, 1227(sh), 1215, 1156, 1022. Cp*HfCl(CH Ph)(PtBu > 2 2 followed except 0.67 (4). g The (1.27 procedure mmol) of 1 for 3 was and 0.17 g (1.31 mmol) of KCH Ph were combined in 25 ml diethyl ether. 2 Workup with petroleum ether mixture afforded 0.54 g IR: 996, 1595, 1583(sh), 812(sh), c 25 H40 ClHfP: 796, (73%) 1484, of reaction crystalline 4. 1197, 1162, 1045, 694(st). Anal. Calcd. C, 51.28; H, 6.89; Cl, 6.05; P, 5.29. C, 51.21; H, 6.96; Cl, 5.96; P, 5.40. Cp*HfMeC1 2 • blue-green of violet, 1360, 743(sh), the Cp*HfC1 3 /.. max 1023, for Found: = 58 0 nrn. (3.705 g, 8.82 mmol) was placed in a flask, and ca. 100 ml of diethyl ether was distilled in at 3.05 ml of 2.9M MeMgBr (8.84 mmol) was syringed into the ether solution at -78°C under argon counterflow, 136 and the reaction mixture was warmed to room temperature. Workup with petroleum 3.05 gm (87%) ether after 57 hours of white crystalline Cp*HfMeC1 • 2 1424, 1150 ( st), 1024 ( st), 799, 540, c 2 460. afforded IR: 1486, Anal. Calcd. for H cl Hf: 11 18 2 C, 33.06; H, 4.54. Found: C, 32.98; H, 4.44. Cp*HfMe cl. 2 The Cp*HfMeC1 g procedure (15.6 for mmol) Cp*HfC1 followed ml of 6.54 MeMgBr (31.9 mrnol) were combined in 100 ml ether. off-white Cp*HfMe Cl. 2 Ca 1 c d • for C IR: H C1 Hf : 12 21 59 1485, C, 3 11 was except with petroleum ether after 1 day and 2 yielded 5.17 g 1138, 38 • 00 ; H, 2. 9 M Workup (88%) of 1023, 802. Anal. 5 • 58 ; Hf , 47 • 07 • was followed Found: C, 37.97; H, 5.66; Hf, 46.99. Cp*HfPhC1 • 2 The procedure for except 1.11 g (2.64 mrnol) Cp*HfC1 (2.64 mrnol) were combined in petroleum ether gave 0.895 g Cp*HfMeC1 3 50 2 and 1.2 ml of 2.2 M PhLi ml ether. Workup (73%) of Cp*PhC1 • 2 with IR: 3050, 1592, 1490(sh), 1480(sh), 1412,1282, 1064(st), 1028,991, 890, 730(st), 703(st). 41.62; H, 4.37. Found: Cp*HfMe ( P t Bu ) 2 2 ( 5). LiPtBu 2 (1.03 g, Anal. Calcd. mrnol) ( 2. 35 were g, placed 60 ml of diethyl ether was distilled in. yellow, then the deep reaction red upon 16 20 a cl Hf: 2 C, 6. 20 mrnol) and in flask and C, 42.03; H, 4.47. Cp*HfMe Cl 2 6.77 for c mixture warming quickly to room a Initially light turned purple, temperature. and After 137 12 hours, ether, the diethyl ether the solution was thoroughly. followed was replaced filtered and (90°C, 1 . 7 6 g of magenta 6 ( 58% ) • I R : 13 58 , Anal. Calcd. C, Found: for c H PHf: 20 39 petroleum and the precipitate was Concentration by sublimation with crystallization at -4 10 torr> yielded 116 6 , 113 4 , 1 0 18 . 49.13; H, 8.04; P, 6.33. C, 48.85; H, 8.45; P, 6.42. The procedure for 5 was followed except 0.495 (1.08 mmol) Workup 1063# c (1.07 LiPtBu with red-purple g 2 and 0.165 g 2 were combined in 30 ml diethyl ether. petroleum mmol) Cp*Hf(Ph)Cl ether afforded 0.275 g IR: 3050, 1361, 1165, 700. Anal. Calcd. for t Cp*HfCl(Ph)(P Bu >. 2 1050, 1022, H clPHf: 24 38 C, 990, 50.44; 720, H, 6.70. Found: C, (44%) of 49.35; H, 6.71. [Cp*HfMe(~-H}(~-P vessel t Bu 11 ~ 2 2 with a teflon (0. 72 mmol) of 5, A thick-walled glass reaction needle 10 ml valve, toluene, charged with and ca. stirred at room temperature for one week. was thoroughly vacuo, yielding washed 0.21 with g of light g 3 atm H was 2 The precipitate petroleum ether and (62%) 0.35 yellow dried in 7. IR: 1510(st), 1485(sh), 1352, 1161, 1132, 1077, 1013, 760(st). C, 37.58. Found: 48.05; C, 48.13; H, 7.86; Hf, 37.54. H, 7.85; Hf, 138 To 7 Reaction of 7 with HCl. 0.3 ml benzene-Q equiv.), and (0.040 g, 0.042 rnmol) and in an NMR tube was condensed HCl (ca. 6 6 the tube was sealed with a torch. Upon warming to room temperature, a vigorous evolution of H and 2 1 CH 4 < H NMR) was observed. The product H2 /CH 4 mixture was passed through a a series of Toepler pump. collected via 0.14 mmol, or 1.7 mmol <H 2 liquid N 2 cooled + + CH 4 >/mmol Hf. traps and amounted to This mixture was cycled over CuO at 320°C to convert H to H o, which 2 2 was removed in a liquid N trap. The remaining CH 4 2 collected amount to 0.070 mmol (0.85 mmol/mmol Hf), or one half of the totalgas collected (i.e., H :cH = 1:1). 2 4 residue obtained after removal of volatiles was The not identified. Structure Determination for [cp*HfMe(~-H)(~-PtBu ll 2 2 (7). Sufficiently large, well formed orange crystals of 7 were obtained from the slow reaction of 5 and H in toluene 2 A single crystal (0.67 x 0.33 x 0.17 mrn) was mounted approximately along the b axis in a glass capillary under N . 2 A series of oscillation and Weissenberg photographs indicated monoclinic symmetry; the space group P2 /c 1 was inferred from systematic absences in the diffractometer data (OkO absent for k odd; hOl absent for 1 odd). Data were collected on a locally-modified Syntex P2 1 diffractometer with graphite monochromator. The unit cell parameters least-squares (Table IV) were obtained by 139 refinement of 15 2S values (46 < 26 < 59°>, where each 2 8 value was an average of two measurements, Intensity data was corrected for a at ± 28. 2.3% linear decay, as indicated by the three check reflections, and the data were 2 reduced to F 0 ; the form factors from reference 58, for all atoms were taken and those for Hf and P were corrected for anomalous dispersion. The details on data collection are given in Table IV. The position of the Hf a tom was derived from the Patterson map, and a series of Fourier maps phased on Hf revealed the remaining non-hydrogen atoms of the complex. Least-squares refinement of minimizing atom gave R coordinates and U's, = All ring 0.084. methyl and phosphide !-butyl methyl H-atoms and the hydride atom were located from difference maps; all H-atoms except the hydride were introduced into coordinates and isotropic U's. the model The with fixed refinement of non-hydrogen atoms in the Hf complex with anisotropic U·~]· 's and the coordinates of the hydride atom with fixed isotropic U using all the data (5678 reflections) led to R = 0.071; the secondary extinction coefficient was refined, giving a value of 0.69(6)xl0- 6 . Robust refinement, with 90 reflections deleted having values of f ina 1 R = 0 . 066 • features I~FI/oF 2 > 6, led to a The final 6. F map showed several large indicative of residual adsorption errors: 0 symmetric pairs of peaks located approximately 0.75 A from the heavy a toms - o3 (,..., Se /A ·- o3 around Hf, - 2e /A around P) • 140 Final atomic coordinates and Uij's are given in Table v. Hydrogen atom coordinates are given in Table VI. Bond distances and bond angles are given in Tables VII VIII, respectively. All calculations and were carried out on a VAX 11/780 computer using the CRYRM system of programs. £E~HfMe(Et)(PtBu 2 ) (8). 0.3 ml in benzene-g 6 To 7 an (0.025 g, 0.027 rnmol) and tube condensed c 2 H4 1~ hours NMR was (0.16 mmol), and the tube was sealed off. at 80°C the solution was deep red; After 1 H NMR indicated a single (>90% pure) soluble product, tentatively identified as the ethylene insertion product 8 . .Lfl2~HfCl(u-H><u-PtBu 2 l.L 2 (9). A solution of Cp*HfCl(Pt- Bu2>2 (2) (0.391 g, 0.55 mmol) in 20 ml toluene was stirred under 1 atm H2 for 3 hours. The solution was filtered, and the light yellow solid was washed thoroughly with toluene and dried in vacuo. Yield: 87%. IR: 1517(st), 1483(sh), 1373, 1358, 1162, 1073, 1017, 834, 806, 770. for c 36 H68 cl Hf P: 2 2 -HI C, 43.64; H, 6.92. Anal. Calcd. Found: C, 43.90; glass reaction 6. 8 8. Cp*HfCl(Et)(PMe ) 3 (11). A thick-walled vessel with a teflon needle valve was charged with 0.527 g (0.996 mmol) of 1, 10 ml toluene, 6.67 rnmol c H4 , 5.00 mmol 2 PMe 3 , and ca. temperature. 3 atm H~ <- 3.6 mmol) and stirred at room After 2 days, petroleum ether workup yielded 141 0. 353 g 12 8 3 , ( 72%) 1 0 22 , of off-white 9 61 ( s t ) , for c 15 a 29 cl 2 HfP: 9 41 , 11. IR: 919 ( s h ) , 1487, 7 32 ( s t ) • C, 36.79; H, 5.97. 1425, 1302, Ana 1 • Ca 1 c d • Found: C, 36.54; H, 5.83. Cp*HfC1 2 <n~C(O)PtBu 2 > <12>. A solution of 0.497 g <0. 9 40 mmol > Cp*HfC1 2 <P tau > <1 > in 15 ml petroleum ether 2 was stirred under 900 torr CO for 20 minutes. washing with cold petroleum yielded 0.380 g of (73%) ether, bright Filtration, and drying in vacuo yellow 12. IR: 1400, 1363(sh), 1350(st, v(C-0)), 1175, 1029, 937, 854, 811, 720, 620 , 5 20 • Ana 1 • Ca 1 cd • 5. 9 6; Cl, 12. 71; P, for C H c 1 Hf 0 P : 19 3 3 2 5. 55. Found: C, 4 0 . 91 ; C, 41. 0 0; H, H, 6. 0 3; Cl, 12.74; P, 5.70. Structure Determination for Cp*HfC1 2 2 cn -c<O>PtBu 2 > <12). A single crystal (0.33 x 0.75 x 0.33 mm> grown from a pentane/benzene solution was mounted in a glass capillary under Oscillation N • 2 indicated orthorhombic was inferred from and symmetry; the Weissenberg the systematic space photographs group absences P2 2 1 2 1 1 in the photographs and in the diffractometer data (hOO absent for h odd; OkO absent fork odd; 001 absent for 1 odd). were collected on a locally-modified Data Syntex diffractometer with graphite monochromator; details on unit cell parameters Table IX. and the data collection are given in Intensity data was corrected for a 1.7% linear 142 decay, as indicated by the three check reflections, and the data were reduced to F 2. 59 0 The position of Patterson map, the Hf atom was derived from the and a series of Fourier maps phased on Hf revealed the remaining non-hydrogen atoms of the complex. Least-squares refinement of atom coordinates and U's, 2 minimizing Lw[F 0 -<F c /k) 2 J 2 , gave R = 0.053. All hydrogens were located from difference maps and introduced into the model with fixed refinement of coordinates and non-hydrogen atoms isotropic in the Hf U's. The complex with anisotropic Uij's using all the data (5760 reflections) led toR= 0.040 and S = 1.66, with refinement of secondary extinction giving coeff. = 0.58(3) x 10- 6 . The final 6 F map showed residual peaks of 1. 0 and 1.2 e-/A 3 associated with the Hf atom. structure with form factors Refinement of the corrected for anomalous dispersion led to the correct assignment of the enantiomer by comparison S=l.73). The of the goodness-of-fit final cycle of (f">O refinement S=2.28; was f"<O based on coordinates of the correct enantiomer (and f" > 0); these are given in · Tables X and XI. Bond distances and bond angles are given in Tables XII and XIII, respectively. 143 TABLE IV. C:cystal and Intensity Collection Data for [Cp*HfMe(l-!-H) (ll-PtBu )] (7). 2 2 Fonnula Formula v.eight C38H74Hf2P2 767.02 g/rrol Space group P2 /c a 11.4848(21) A b 16.4472(52) A c 11.8255(22) A s 118~915(11) 0 v 3 1955.1 .A z 4 0 1.61 g/an 1 0 0 0 calc Crystal size 3 0.67 X 0.33 X 0.17 rom 0 A - ll 0.71069 A (Mo Ka) 5.36 mm-l Scan range 1. 0° below ~ , 1.1° above Ka Refln settings +h, +k, !_1 28 range, scan rate, 3.5<28<36° 4.88°/rnin 1.0 3143 number of reflns 35 <28<46° 2.02°/min 0.5 6323 Total number of averaged data Refinanent on 5678 2 F Final number of parameters 195 Final cycle: t Total Data Set Ibbust Refinanent R 0. 071 (5503) 0.066 (5413) R' 0.064 (4693) 0.059 (4603) s 4.02 3.55 1 2 backgrd tirre/scan tine, 0 (5678) (5588) t Typical R-value, number of reflns used in sums given in parentheses. R' refers to R-value calculated for reflns with F~ > 3crF2. s is the gcx:>dness-of-fit; surrma.tions include all reflns. deleted reflns with IM' II crF2 > 6. Robust refinanent Table v. 4 Final non-hydrogen atom c~ordinates (x 10 ) X Hf p C(M) C(1) C(2) C(3) C(4) C(5) C(1M) C(2M) C(3M) C(4M) C(5M) C(PA) C(PA1) C(PA2) C(PA3) C(PB) C(PB1) C(PB2) C(PB3) 1291.8(3) -1183(2) 1172(8) 3720(7) 3700(8) 3003(8) 2545(8) 3013(8) 4633(9) 4530(10) 2917(11) 2008{9) 2991(10) -1564(9) - 2973( 11) -562(11) -1490(11) -1964(8) -1015(10) -2082(11) -3350(10) y z 276.8(3) 544.1(2) -1978(2) 605( 1) 1226(8) 1709(5) 983{8) 204(5) 1221(8) 1061( 5) 39(9) 1452( 5) -968(8) 873(5) -354(8) 94(5) 1982(11) -393(7) 2506(10) 1477(8) -155(10) 2368(6) - 2361(9) 1086(6) -685(6) -1047(10) -3621(7) 140{6) - 4242(9) - 236(7) - 3367(9) -526(6) -4599(9) 727(7) - 2294(8) 1679( 5) 2272(6) -2439(11) 1929( 6) - 1119( 11) 1766(7) - 3477( 10) 4 and Gaussian amplitudes (x 10 ). [!22 [!33 []12 [!13 []2;3 194{1) 232(1) 270(8) 244(8) 363(39) 330(39) 405( 41) 386( 40) 331(38) 392(42) 6(39) 290(37) 20(36) 376(39) 4(36) 360(39) 377(45) 556(59) 493(53) 733(75) 654(62) 327(43) 453(47) 491(50) 466(48) 372{45) 434(44) 490(49) 513( 56) 614( 63) 655(60) 517(53) 569( 57) 697(70) 396(40) 282(36) 474(50) 350(44) 563{56) 348(43) 445(48) 514{57) 235(1) 239(8) 362(38) 9(28) 398(42) 476(45) 339(37) 404( 41) 591(58) 433(50) 521(53) 400{44) 588(55) 223{33) 364( 45) 413{45) 334( 41) 403(41) 709(66) 648(62) 508(53) -3(1) 27(7) -57(32) 134(30) -83(33) -46(29) -49(30) 64(30) 94( 40) -232(51) -98( 42) 32{39) - 2{36) - 23(37) -103( 47) 48( 48) 32{49) 84(32) 57(39) 108(40) 107(42) 103( 1) 113(7) 97(32) 112(34) 164(34) 223(36) 198(32) 222(33) 205( 43) 163{43) 251( 48) 224(39) 294{ 45) 137(32) 92( 42) 323( 45) 211(41). 144(34) 220( 48) 325(51) 150(42) 1(1) 38(7) -107(34) 338(16) -23(36) 7(33) 36(32) 59(33) 238( 48) -117(51) 47(42) 106( 41) -46( 41) 18(34) -100( 46) - 46( 45) 120( 45) 125{34) 192( 48) 92( 44) 169(47) [!11 . ~ ~ ~ 145 Table VI. Hydrogen atom coordinates (x 10 3 ) • H H(1) H(2) H(3) H(4) H(5) H(6) H(7) H(8) H(9) H(10) H(11) H(12) H(13) H(14) H(15) H(16) H(17) H(18) H(19) H(20) H(21) H(22) H(23) H(24) H(25) H(26) H(27) H(28) H(29) H(30) H(31) H(32) H(33) H(34) H(35) H(36) X y z 424(118) 2077 585 851 -3623 -2951 -3237 -883 290 -459 -654 -2240 -1553 -95 -1224 -1093 -1408 -2967 -1912 -3400 -3524 -4039 4144 5075 5350 4957 3981 5243 3692 2101 2885 2700 1803 1213 2199 3793 2994 -751(73) 1976 2116 1623 125 -757 -350 -1046 -386 -608 1030 1127 433 2152 2840 2230 2370 2167 1479 2274 1304 1780 -864 -125 -574 1059 1829 1810 2566 2504 2645 1397 592 1427 -1016 -1013 -572 -463(117) 1706 571 1842 -4934 -4689 -3616 -3208 -2657 -4165 -4156 -4900 -5329 -1786 -2315 -3305 ' -657 -1389 -553 -3957 -4080 -3223 2051 2879 1829 3209 2751 2516 -221 -968 563 -2467 -2888 -2680 -1246 -497 -1871 146 Table VII. Bond lengths for [Cp*HfMe(l.l-H) (11-PtBu )] t-< Hf-Hf' Hf-"R1 Hf-C(M) Hf-H' Hf-H Hf-P Hf-P' Hf-C(1) Hf-C(2) Hf-C(3) Hf-C(4) Hf-C(5) C(1)-C(5) C(1)-C(2) C(2)-C(3) 3.250 2.264 2.258(9) 2.33(13) 2.12(13) 2.805(2) 2.807(2) 2.557(9) 2.575(9) 2.589(9) 2.564(9) 2.537(9) 1.396(12) 1.439(13) 1.388(13) C(3)-C( 4) C(4)-C(5) C(1)-C(1M) C(2)-C(2M) C(3)-C(3M) C(4)-C(4M) C(5)-C(5M) P-C(PA) P-C(PB) C(PA)-C(PA1) C(PA)-C(PA2) C(PA)-C(PA3) C(PB)-C(PB1) C(PB)-C(PB2) C(PB)-C(PB3) 1..413( 1:1) 1.442(12) 1.;304( 14) 1.512(15) 1.520(14) 1.495(13) 1.514(14) 1.931(10) 1.933(9) 1.546(15) 1.509(15) 1.541(15) 1..534( 15) 1.517(15) 1.536(14) aR1= ring centroid of Cp*-ring [atoms C(1)-C(5M)]. 2 0 2 (A) • 147 H-Hf-H~ P-Hf-P ~ (IR1-Hf-C(M) Rt-Hf- H' R1-Hf-H · R1-Hf-P R1-Hf-P~ C(M)-Hf-H' C(M)-Hf-H C(M)-Hf-P C(M)-Hf-P ~ H-Hf·-P H~Hf-P' H -Hf-P~ Hf-H-Hf~ Hf-P-Hf~ C(PA)-P-C(PB) C(PA)-P-Hf C(PA)-P-Hf~ C(PB)-P-Hf C(PB)-P-Hf~ C(PA1)-C(PA}-C(PA2) C(PA1)-C(PA)-C(PA3) C(PA2)-C(PA)-C(PA3) 86 (5) 109.2(1) 101.4(2) . 111 (3) 162 (4) 120.5( 1) 120.5(1) 147 (3) 62 (4) 99.5(2) 100.4(2) 68 (3) 62 ( 4) 71 ( 4) 94 (5) 70.8( 1) 108.0( 4) 125.1(3) 112.8(3) 112.2(3) 125.2(3) 109.1(8) 108.6(8) 106.8(8) C(PA1)-C(PA)-P C(PA2)-C(PA)-P C(PA3)-C(PA)-P C(PB1)-C(PB)-P C(PB2)-C(PB)-P C(PB3)-C(PB)-P C(2)-C(1)-C(5) C (3 )-C (2)--C ( 1 ) C( 4)-C(3)-C(2) C( 5)-C( 4)-C(3) C( 1)--C( 5 )-C( 4) C(1M)-C(1)-C(5) C( 1M)-C( 1)-C( 2) C( 2M)-C( 2)-C( 1) C( 2M)-C( 2)-C( 3) C( 3M)-C( 3 )-C( 2) C(3M)-C(3)-C( 4) C( 4M)-C( 4)-C(3) C( 4M)-C( 4 )-C( 5) C( 5M)-C( 5 )-C( 4) C( 5M)-C( 5 )-C( 1) C( PB 1)-C( P B )-C( PB2) C(PB1 )-C(PB)-C(PB3) C(PB2 )-C(PB )-C(PB3) = ring centroid of Cp *-ring [atoms C(1)-C(5M). GR 1 10~.:2(7) 107 .9(7) 116.1(7) 108.3(7) 108.0(7) 116.2(7) 107 .1(8) 108.2(8) 109.5(8) 106.2(8) 109.0(8) 127.4(8) 123.8(8) 125.3(9) 125.4(9) 125.1(9) 124.8(8) 12~1.9(8) 128 .2(8) 123.1(8) 12-!.8(8) 108.2(8) 108.6(8) 107 .3(8) 148 TABLE IX. Crystal and Intensity Collection Data for Cp*HfC1 (n2-c(O)PtBu ) (12). 2 2 c H c1 HfOP 19 33 2 557.83 P2 2 2 1 1 1 0 14.9191(15) A 0 9.9521(10) A 0 15.7794(18) A 2342.8 X3 Fonrula Fonnula weight Space group a b c v z 4 1.64 g/an3 0.33 x 0.75 x 0.33 ([lOO]x[OlO]x[OOl]) 0 0.71069 A (Mo Ka) 4.85 nm-l 0 calc Crystal size A. 1-1 Scan range 28 limi.ts, scan rate, backgrd tine/scan time, number of reflns Total nunber of averaged data Fefinement on Final number of pararreters Final agrement R (F2 > 0) 0 R' s 1.2° below K~, 1.2° al:ove Ka 2 4-35° 1107 (+h,+k,±_1) 2.02°/min 738 (+h,+k,±_l) 17-35° 3.91°/min 34-46° 2746 (+h,+k,±_l) 2.93°/min 4-36° 45-50° 45-56° 5760 F2 4.88°/min 2.02° /min 2.02°/min 1881 (+h, -k,±_1) 1160 (+h,+k,±_1) 1760(+h,+k,±_1) 0 218 0.040 (5570) t 0.030 (4609) 1.66 (5760) t Typical R-value, number of reflns used in sums given in parentheses. R' refers to R-value calculated for reflns with F~ > 3aF2. S is the goodness of fit. 4 4 Table X. Final non-hydrogen atom coordinates (x 10 ) and Gaussian amplitudes (x 10 ) . U12 ul3 U23 343( 1) -17(1) -15(1) 29(1) 392(7) 473(7) 13(7) 25(6) -10(6) 854(13) 787(11) 515(8) -72(10) 176(8) 80(8) 6925(1) 624( 11) 827(12) 721(10) 38(10) -217(8) 149(9) 7661(5) 8526(3) 426(32) 417(27) 434(26) 46(27) -1(27) 84(21) 8515(3) 7397(4) 8235(2) 433(25) 504(23) 560(23) -29(20) -8(19) -44(19) C(1) 7026( 4) 4233(6) 8368(4) 604( 41) 495(37) 565(35) 53(29) 142(30) 143(27) C(2) 7863(5) 4539(5) 8736(3) 827(53) 339(28) 383(28) 22(30) -85(29) ~4(22) C(3) 8527( 4) 4242(6) 8151(4) 535( 40) 486(37) 628(38) 9(29) -23(32) 71(29) C(4) 8112(5) 3731( 5) 7418(4) 838( 44) 387(27) 428(30) 56(26) 13(34) -57(36) C(5) 7182(4) 3729(5) 7554(4) 700( 45) 446(28) 542(30) -98(26) - 241(37) 84(39) C(lM) 6118(6) 4~59(8) 8799(6) 915(68) 887(60) 1597(83) 129(51) 618(61) 508(59) C(2M) 8030(7) 4989(6) 9649( 4) 1767(94) 589( 42) 431(34) 117(50) -71(46) 1(29) C(3M) 9522(5) 4390(8) 8276(6) 618(55) 881( 59) 1575(80) 57( 45) - 281( 53) 291( 56) C(4M) 8583(7) 3146(8) 6653( 5) 1668(96) 649(49) 732( 48) , 168(57) 37 4( 55) -55( 40) C(5M) 6494(7) 321 :3(8) 6945(5) 1432(85) 650( 48) 1257(70) -412(55) -710(64) 136( 48) C(PA) 8485( 4) 9972(6) 9430(5) 523( 43) 451(36) 908(50) -32(30) -70(36) -186(33) C(PA1) 9318(5) 9153(8) 9699(5) 525(44) 920(58) 1015( 53) 42(42) -172(39) -111(46) C(PA2) 8685(6) 10627(7) 8572(6) 769(60) 648( 48) 1641(82) - 257( 44) 7(57) 369(51) C(PA3) 8312( 6) 11038( 10) 10085(7) 812(67) 1102(70) 2413(122) -144(61) 35(72) -1096(81) C(PB) 6423( 4) 9483(6) 9153( 4) 414(37) 653( 41) 734( 42) 69(33) 78(31) 24(35) C(PB1) 616g(6) 10486(10) 9821(6) 737(64) 1186(7 4) 1589(86) 362(60) 203(60) -311(64) C(PB2) 5765( 5) 8311(8) 9175(5) 543( 46) 966(54) 915(51) -70(43) 35(38) 66( 44) C(PB3) 6371(5) 10165(8) 8296(5) 650(53) 924(57) 1196(66) 143(45) -135(47) 359(51) X y z Uu U22 Hf p 7663.7(1) 61 03.5( 2) 7536.5( 1) 471(1) 395(1) 7541(1) 87 45(1) 9407 .3(8) 504( 10) Cl(1) 8587( 1) 6558(2) 6330.2(9) Cl(2) 6255( 1) 6681(2) c 7730(4) 0 Uaa 1--' ~ ~ 150 Table XI. Hydrogen atom coordinates (x 10 3 ) • y z 5885 5341 8806 5620 3836 8545 6141 4112 9416 8414 4289 9949 5160 9949 7511 8433 5821 9637 9773 3673 8620 9636 5270 8620 9851 4500 7752 8528 2134 6654 9237 3342 6654 8330 3468 6117 6276 3936 6564 6766 2503 6564 5989 2811 7238 9198 8188 9563 9445 9246 10292 9851 9425 9359 9369 10739 8513 8415 11480 8513 8509 10002 8120 8740 11760 10094 7706 11329 10094 8406 10558 10692 6531 11327 9790 5514 10807 9790 6235 10135 10412 5199 8475 8879 6051 7493 8879 5640 8013 9758 6916 9960 7955 5850 9765 7932 6272 11110 8322 X H(1) H(2) H(3) H(4) H(5) H(6) H(7) H(8) H(9) H(10) H(11) H(12) H(13) H(14) H(15) H(16) H(17) H(18) H(l9) H(20) H(21) H(22) H(23) H(24) H(25) H(26) H(27) H(28) H(29) H(30) H(31) H(32) H(33) 151 Table XI-I. Bond lengths for Cp*HfC1 2 2 t (n -C (0) P Bu ) 2 Hf-aR1 2.157 C(2)-C(3) 1.386(9) Hf-Cl(1) 2.393(2) C(3)-C( 4) 1.407(9) Hf-Cl(2) 2.383(2) C(4)-C(5) 1.404(8) Hf-C 2.203(5) C(1)-C(1M) 1.521( 11) Hf-0 2.117(4) C(2)-C(2M) 1.528(9) Hf-C(1) 2.468(6) C(3)-C(3M) 1.506(11) Hf-C(2) 2.469{6) C(4)-C(4M) 1.513( 10) Hf-C(3) 2.456(6) C(5)-C(5M) 1.497(11) Hf-C(4) 2.461(6) C(PA)-C(PA1) 1.546{10) Hf-C(5) 2.471(6) C(PA)-C(PA2) 1.533( 11) C-0 1.284(6) C(PA)-C(PA3) 1.503(12) P-C 1.782(5) C(PB)-C(PB1) 1.500(11) P-C(PA) 1.864(7) C(PB)-C(PB2) 1.525(10) P-C(PB) 1.866(7) C(PB)-C(PB3) 1.516( 10) C(1)-C(5) 1.398(8) C(1 )-C(2) 1.410(8) =ring centroid of Cp*-ring [atoms C(1)-C(5M)]. aR 1 0 (A). 152 2 t Table XIII. Bond angles for Cp*HfC1 2 (n -C(O)P Bu 2 ) aR 1 ( 0 ). aR1-Hf-CI(1) 116.1(1) C(1M)-C(1)-C(5) 126.1(6) R1-Hf-CI(2) 114.9(1) C( 1M)-C( 1)-C( 2) 125.9(6) RI-Hf-C 112.7(1) C( 2M)-C( 2)-C( 1) 126.6( 5) RI-Hf-0 109.7{1) C( 2M)-C( 2)-C( 3) 125.0(6) Cl(1)-Hf-CI(2) 98.1( 1) C( 3M)-C( 3 )-C( 2) 126.7(6) Cl(1)-Hf-C 113.9(1) C{3M)-C(3)-C( 4) 125.2(6) Cl(1)-Hf-O 87.4(1) C( 4M)-C( 4)-C(3) 126.2(6) CI(2)-Hf-C 99.1(1) C( 4M)-C( 4)-C( 5) 125.4( 6) Cl(2)-Hf-O 126.4(1) C(5M)-C(5)-C( 4) 125.5(6) C-Hf-0 34.5(2) C( 5M)-C( 5)-C( 1) 126.8(6) Hf-C-P 166.4(3) P-C(PA)-C(PA1) 105.5( 5) Hf-C-0 69.1(3) P-C(PA)-C(PA2) 114.1(5) P-C-0 123.2( 4) P-C(PA)-C(PA3) 110.3( 5) Hf-0-C 76.4(3) C(PA1 )-C(PA)-C(PA2) 108.1(6) C-P-C(PA) 107.0(3) C(PA1 )-C(PA)-C( PA3) 108.8(6) C-P-C(PB) 102.3(3) C(PA2)-C(PA)-C(PA3) 109.9(6) C(PA)-P-C(PB) 114.9(3) P -C(PB )-C(PB 1) 109.8(5) C(2)-C(1 )-C( 5) 108.0( 5) P-C(PB)-C(PB2) 10.5.6(4) C(3)-C(2)-C(1) 108.1(5) P-C(PB)-C(PB3) 114.4( 5) C( 4)-C(3)-C(2) 108.1( 5) C(PB1 )-C(PB)-C(PB2) 109.3(6) C(5)-C( 4)-C(3) 108.0( 5) C(PB1 )-C(PB)-C(PB3) 108.4(6) C( 1)-C( .5)-C( 4) 107.7(5) C( PB2 )-C( PB )- C( PB3) 109.3(6) =ring centroid of Cp*-ring [atoms C(l)-C(5M)]. 153 REFERENCES (1) (a) Cardin, D. J.; Lappert, M. F.; Raston, C. L.; Riley, P. I. "Comprehensive Organometallic Chemistry"; Wilkinson, G., ed., Pergamon Press: New York, 1982; Vol. 3, 559-634. Weigold, H. (b) Wailes, P. C.; Coutts, R. S. P.; "Organometallic Chemistry of Titanium, Zirconium and Hafnium"; Academic Press: New York, 1974. (c) Andersen, R. A. Inorg. Chern. 1979, la, 2928; Ibid. J. Organomet. Chern. 1980, lil, 189; Planalp,R. P.; Andersen, R. A.; Zalkin, A. Organometallics 1983, 2, 16. Ibid. 1982, l, 1025. Bercaw, J. E. (2) (d) Hillhouse, G. L.; (a) Ellerman, J.; Poersch, P. Ed. Engl. 1967, ~, 355. Angew. Chern. Int. (b) Stelzer, 0.; Unger, E. Chern. Ber. 1977, llQ, 3430; Johannsen, G.; Stelzer, 0. (3) Ibjd., 3438. (a) Jones, R. A.; Wright, T. L.; Atwood, J. L.; Hunter, W. E. Organometalljcs 1983, 2, 470. (b) Finke, R. G.; Ganghan, G.; Pierpont, C.; Cass, M. E. J. Am. Chern. Soc. 1981, l[l, 1394. (c) Roberts, D. H.; Steinmetz, G. R.; Breen, M. J.; Shulman, P. M.; Morrison, E. D.; Duttera, M. R.; DeBrosse, Whittle, R. R.; Geoffroy, G. L. c. W.; Organometalljcs 1983, 2, 846 and references therein. (4) (a) Lappert, M. F.; Power, P. P.; Sanger, A. R.; Srivastava, R. C. "Metal and Metalloid Amides"; Ellis Horwood Ltd.,Chichester,l980. 154 (b) Bradley, D. C.; Chisholm, M. H. Ace. Chern. Res. 1976, i, 273. (5) (a) Domaille, P. J.; Foxman, B. M.; McNeese, T. J.; Wreford, S. S. J. Am. Chern. Soc. 1980, !Dl, 4114. (b) Rocklage, s. M.; Schrock, R. R.; Churchill, M. R.; Wasserman, H. J. (6) Organometallics 1982, ~, 1332. Quite recently, a number of early transition metal complexes containing terminal phosphido ligands have been reported. (a) Baker, R. T.; Whitney, J. F.; Wreford, S. S. Organometallics 1983, 2, 1049. (b) Baker, R. T.; Krusic, P. J.; Tulip, T. H.; Calabrese, T C.; Wreford, S. 1983, ~, 6763. s. J. Am. Chern. Soc. (c) Jones, R. A.; Lasch, J. G.; Norman, N. C.; Whittlesey, B. R.; Wright, T. C. Ibid., 6184. (7) Wolczanski, P. T.; Bercaw, J. E. ~, (8) Organometallics 1982, 793. The steric influence of ptBu 2 in bridging metal systems has recently been investigated: Jones, R. A.; Stuart,A. L.; Atwood, J. L.; Hunter, W. E.; Rogers, R. D. Organometallics 1982, ~, 1721; Ibid. 1983, 2, 874; Atwood, J. L.; Hunter, W. E.; Jones, R. A. (9) Inorg. Chern. 1983, 22, 993. Calculated from the Gutowsky-Holm approximation ~G+ ~ 15 + 0.05 Tc <°C), where Tc is the coalescence temperature. (10) Couturier, S.; Gautheron, B. 157, C61. J. Organomet. Chern. 1978, 155 (11) Roddick, D. M.; Fryzuk, M. D.; Seidler, P. F.; Hillhouse, G. L.; Bercaw, J. E., manuscript in preparation. (12) Gel!, K. I.; Schwartz, J. J. Am. Chern. Soc. 1978, l.Q.Q, 3246. (13) Simpson, s. J.; Turner, H. W.; Andersen, R. A. J. Am. Chern. Soc. 1979, (14) ~' 7728. Anomalously high bridging hydride stretches have been noted for [Cp 2 TiHJ 2 (1450 cm-1)14a and binuclear tantalum hydride complexes (1580-1600 cm-1) ,14b (a) Bercaw, J. E.; Brintzinger, H. H. 1969, il, 7301. Day, C. S. ( 15) J. Am~ Chern. Soc. (b) Belmonte, P. A.; Schrock, R. R.; J. Am. Chern. Soc. 1982, ~' 3082. Lokshin, B. · V.; Klemenkova, Z. S.; Ezerni tskaya, M. G.; Strunkina, L. I.; Brainina, E. M. J. Organomet. Chern. 1982, 2..3..5., 69. (16) Wailes, P. C.; Weigold, H. J. Organomet. Chern. 1970, 2.J., 405. (17) Manriquez, J. M.; McAlister, D. R.; Sanner, R. D.; Bercaw, J. E. (18) J. Am. Chern. Soc. 1976, ia, 6733. Blenzers, J., Ph.D. Thesis, Ryksuniversiteit te Groningen, 1982. (19) Chapter 2 of this thesis. (20) Hunter, w. E.; Hrncir, D. C.; Vann Bynum, R.; Pentilla, R. A.; Atwood, J. L. 2., 750. Organometallics 1983, 156 (21) Fronzek, F. R.; Baker, E. C.; Sharp, P. R.; Raymond, K. N.; Alt, H. G.; Rausch, M. D. Inorg. Chern. 1976, 15., 2284. (22) Atwood, J. L.; Hunter, w. E.; Hrncir, D. C.; Samuel, E.; Alt, H. G.; Rausch, M. D. (23) Inorg. Chern. 1975, l!, 1757. Jones, S. B.; Petersen, J. L. Inorg. Chern. 1981, lQ, 2889. (24) Johnson, P. L.; Cohen, Williams, J. M. (25) s. A.; Marks, T. J:; J. Am. Chern. Soc. 1978, ~' 2709. w. C.; Keiderling, T. A.; ~y, w. J.; LaPlaca, s. J.; Lippard, s. J.; Bernstein, E. R.; Hamilton, Marks, T. J.; Mayerle, J.J., unpublished results, reported in the Ph.D. dissertation of Keiderling, T. A., Princeton University, 1974. (26) Chapter 2 of this thesis. (27) The -0.35 A difference between bridging and terminal 0 hydride bond lengths for 7 and Cp 2* Hf(H) (n 3 -cH 2CHCH 2 ) is 0 higher than the 0.1-0.2 A difference normally observed (see reference 28). (28) Bau, R.; Carroll, W. E.; Teller, R. G.; Koetzle, T. F. J. Am. Chern. Soc. 1977, ii, 3872. (29) (a) This -0.3 A lengthening going from terminal to ~-PR 2 coordination contrasts markedly with terminal and bridging Mo-P values for Mo 2 cptsu 2 > 2 C~-Ptsu2>29b CMo-PCterminal) = 2.382(1) Mo-PCbridge) 0 only 0.06 A. A, 0 = 2.437(1), 2.434(1) A), which differ by (b) Jones, R. A.; Lasch, J. G.; 157 Norman, N. C.; Whittlesey, B. R.; Wright, T. C. J. Am. Chern. Soc. 1983, ~, 6184. (30) Closest intramolecular nonbonding C-H contacts are 0 c (PB2)-H (22) I c (PB3)-H (22) = 2. 71 A. (31) Defining t~ as the time at which the ptBu 2 resonance is half the integral value at t=O, at 25°C, - 3 at m H2 , t~ ~ 5 min. (32} Lappert, M. F.; <2 > , 1 3 min. ( 3 > , 7 h r • Patil, D. S.; Pedley, J. <4 > • B. J.C.S. Chern. Commun. 1975, 830. (33) Tentatively identified by lH NMR. (34} Although no adduct of 1 with PMe3 was observed down to -70°C, variable temperature lH NMR revealed a steady downfield shift <A& = 0.3 ppm at -70°C> for the ~-butyl resonances, suggestive of an equilibrium involving a metal-phosphine interaction. No similar shift was observed for 1 in the absence of PMe3· (35) Fagan,P.J;Manriquez, J. M.; Marks, T. J.; Day, v. W.; Vollmer, s. H.; Day, C. s. J. Am. Chern. Soc. 1980, !QZ, 5393. (36) Fachinetti, G.; Floriani, C.; Marchetti, F.; Merlino, s. J.C.s. Chern. Comm. 1976, 522. (37) Erker, G.; Rosenfeldt, F. 19781 lit 605 (38) Angew. Chern., Int. Ed. Engl. e Lappert, M. F.; Luong-Thi, N. T.; Milne, C. R. C. J. Organomet. Chern. 1979, 174, C35. (39) Fagan, P. J.; Manriquez, J. M.; Vollmer, S. H.; Day, C. S.; Day, V. W.; Marks, T. J. 1981, 1..0..3., 2206. J. Am. Chern. Soc. 158 (40) Cramer, R. E.; Maynard, R. B.; Paw, J. C.; Gi1je, J. w. Organorneta11ics 1982, ~' 869. (41) Moore, E. J., Ph.D. Thesis, California Institute of Technology, 1984. (42) Using the Eyring equation, with kcCexchange) rate at coalescence temperature Csec-1)) calculated from the Gutowsky-Holm relation: Holm, C. H. (43) = ~6vi Gutowsky, H. S.; kc J. Chern. Phys. 1956, ~' 1228. See reference 45 of Marks ~ ~' reference 39 of this chapter. (44) Values reported for hindered rotation in organic amides range from 15-30 kcal.44a Although direct measurement of acylphosphine rotational barriers has not been reported,44b calculations44c suggest an upper limit of -6 kcal. (a) Kessler, H. 1970, i, 219. Angew. Chern., Int. Ed. Engl. (b) Egan, W.; Mis1ow, K. Chern. Soc. 1971, J. Am. il, 1805; Kostyanovskii, R. G.; Elnatanov, Y. I.; Zakharov, K. S.; Zagurskaya, L. M. Dokl. Akad. Noyk. SSSR (Eng>. 1974, lli, 1021. (c) Dougherty, D. A.; Mislow, K.; Whangbo, M.-H. Tetrahedron Lett. 1979, 2321. (45) Sa1darriaga-Molina, C. H.; Clearfield, A.; Bernal, I. Inorg. Chern. 1974, (46) Raymond, K. N.; Eigenbrot, Jr., C. W. 1980, (47) ll, 2880. Ace. Chern. Res. ll, 276. Shannon, R. D. Acta. Crysta11ogr. 1976, 12a, 751. 159 (48) (a) Tranqui, D.; Laugier, J.; Boyer, P.; Vulliet, P. Acta. Crystallogr. 1978, JJB, 767; Tranqui, D.; Tissier, A.; Laugier, J.; Boyer, P. 392. Ibid. 1977, 11Q, (b) Stutte, B.; Batzel, V.; Boese, R.; Schmid, G. Chern. Ber. 1978, lll, 1603. (c) Fronczek, F. R.; Baker, E. C.; Sharp, P. R.; Raymond, K. N.; Alt, H. G.; Rausch, M. D. (49) Inorg. Chern. 1976, ~' 2284. Smith, W. F.; Taylor, N.J.; Carty, A. J. J.C.S. Chern. Comm. 1976, 896. (50) Becker, H.-J.; Fenske, D.; Langer, E.; Prokscha, H. Monatsh. Chern. 1980, lll, 749. (51) Khaikin, L. S.; Andrutskaya, L. G.; Grikina, 0. E.; Vilkov, L. V.; El'Natov, Y. I.; Ko·styanovskii, R. G. J. Mol. Struct. 1977, 11, 237. (52) Roddick, D. M., unpublished results. (53) Marvich, R. H.; Brintzinger, H. H. J. Am. Chern. Soc. 1971, i,i, 2046. (54) Hoffmann, H.; Schellenbeck, P. Chern. Ber. 1966, ii, 1134. (55) Brown, T. L.; Dickerhoof, D. W.; Bafus, D. A.; Morgan, G. L. (56) Rev. Sci. Instrum. 1962, ll, 491. Molecular weight determined by isothermal distillation using the Singer method. (a) Singer, R. Liebigs Ann. Chern. 1930, Jla, 246. Justus (b) Clark, E. P. Ind. Eng. Chern .• Anal. Ed. 1941, ll, 820. (57) Prolonged metathesis resulted in significant Cl ;= Br exchange, as judged by elemental analysis. 160 (58) International Tables for X-Ray Crystallography, Vol_. IV, 1974, pp. 72-98. (59) (a) The data were also corrected for absorption by the method of Gaussian quadrature 59b for the 2120 reflections with multiple observations, the goodness-offit was reduced to 3.25 from 3.56 from the correction alone. (b) Busing, Crystallogr. 1957, w. R.; Levy, H. A. ~' 180. Acta.