Synthesis of Titanium, Zirconium, and Hafnium Complexes that Contain Diamido Donor Ligands of the Type [(t-BuN-o-C6H4)2O]2- and an Evaluation of
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- 作者：Richard R. Schrock ; Robert Baumann ; Steven M. Reid ; Jonathan T. Goodman ; Rü ; diger Stumpf ; and William M. Davis
- 刊名：Organometallics
- 出版年：1999
- 出版时间：August 30, 1999
- 年：1999
- 卷：18
- 期：18
- 页码：3649 - 3670
- 全文大小：374K
- 年卷期：v.18,no.18(August 30, 1999)
- ISSN：1520-6041
文摘
Titanium, zirconium, and hafnium dialkyl complexes that contain the [(t-Bu-d6-N-o-C6H4)2O]2- ([t-BuNON]2-) ligand have been prepared. Only [t-BuNON]TiMe2 could beisolated, but [t-BuNON]ZrR2 and [t-BuNON]HfR2 complexes could be isolated in which (forexample) R = Me, Et, or i-Bu. X-ray studies showed [t-BuNON]MMe2 structures (M = Ti orZr) to be of the "twisted fac" variety in which two amido nitrogens occupy equatorial positionsin a distorted trigonal bipyramid. However, in solution all such species show equivalentalkyl groups on the NMR time scale as a consequence of formation of an intermediate merstructure that contains a planar oxygen donor. In analogous complexes that contain the{[Me(CD3)2CNC6H4][Me(CD3)2CN-2,4-Me2C6H2]O}2- or {[Me(CD3)2CNC6H4][Me(CD3)2N-2-EtC6H3]O}2- ligand the two metal alkyl groups are inequivalent on the NMR time scale.Addition of trimethylphosphine to [t-BuNON]Zr(CH2CH3)2 yields structurally characterized,pseudooctahedral [t-BuNON]Zr(
2-C2H4)(PMe3)2. Addition of B(C6F5)3 to [t-BuNON]ZrMe2yields structurally characterized {[t-BuNON]ZrMe}[MeB(C6F5)3], while addition of [PhNMe2H][B(C6F5)4] to [t-BuNON]ZrMe2 in bromobenzene-d5 generates "{[t-BuNON]ZrMe(PhNMe2)][B(C6F5)4]", which is an active catalyst for the polymerization of up to 500 equiv of 1-hexenein a living manner at 0 
C. The analogous hafnium systems are not as well behaved, sincethe dimethylaniline is insufficiently labile. No polymerization activity is observed for activatedtitanium dialkyl complexes. Polymerization activity is quenched upon addition of THF ordimethoxyethane to the cationic complexes. An X-ray structure of {[t-BuNON]ZrMe(THF)2][B(C6F5)4] shows it to be a pseudooctahedral species in which the [t-BuNON]2- ligand adoptsa "twisted mer" geometry, while the X-ray structure of {[t-BuNON]ZrMe(MeOCH2CH2OMe)][B(C6F5)4] was found to be of the "twisted fac" variety. In the case of hafnium, pseudooctahedral cationic bis-THF or DME complexes can be isolated even when the anion is [B(C6H5)4]-;like all complexes that contain THF or DME they are essentially inactive for polymerizationof 1-hexene.
2-C2H4)(PMe3)2. Addition of B(C6F5)3 to [t-BuNON]ZrMe2yields structurally characterized {[t-BuNON]ZrMe}[MeB(C6F5)3], while addition of [PhNMe2H][B(C6F5)4] to [t-BuNON]ZrMe2 in bromobenzene-d5 generates "{[t-BuNON]ZrMe(PhNMe2)][B(C6F5)4]", which is an active catalyst for the polymerization of up to 500 equiv of 1-hexenein a living manner at 0 C. The analogous hafnium systems are not as well behaved, sincethe dimethylaniline is insufficiently labile. No polymerization activity is observed for activatedtitanium dialkyl complexes. Polymerization activity is quenched upon addition of THF ordimethoxyethane to the cationic complexes. An X-ray structure of {[t-BuNON]ZrMe(THF)2][B(C6F5)4] shows it to be a pseudooctahedral species in which the [t-BuNON]2- ligand adoptsa "twisted mer" geometry, while the X-ray structure of {[t-BuNON]ZrMe(MeOCH2CH2OMe)][B(C6F5)4] was found to be of the "twisted fac" variety. In the case of hafnium, pseudooctahedral cationic bis-THF or DME complexes can be isolated even when the anion is [B(C6H5)4]-;like all complexes that contain THF or DME they are essentially inactive for polymerizationof 1-hexene.