Investigation of the role of hydrides in zirconocene catalyzed olefin polymerization |
Posted on:2012-09-13 | Degree:Ph.D | Type:Dissertation |
University:California Institute of Technology | Candidate:Baldwin, Steven M | Full Text:PDF |
GTID:1451390011450912 | Subject:Inorganic Chemistry |
Abstract/Summary: | |
The structure and reactivity of zirconocene hydrides in the presence of aluminum alkyls is investigated for both neutral species and cationic species. Unbridged zirconocene dichlorides react with HAliBu 2 to yield trihydride dialuminum clusters of the general formula (R nC5H5-n)2Zr(mu-H)3(Al iBu2)3(mu-Cl)2. Bridged zirconocenes instead predominantly yield a dihydride monoaluminum cluster of the general form Me2E(RnC5H4-n) 2Zr(Cl)(mu-H)2AliBu 2 where E = Si or C. For tert-butyl substituted zirconocenes the terminal Cl is replaced by a H. It is shown that steric factors dictate which hydride is formed.;A single type of cationic trihydride dialuminum cluster of general formula [(RnC5H4-n)2Zr(mu-H)3(Al iBu2)2]+ is formed for all zirconocene hydrides upon addition of [Ph3C][B(C6F 5)4] regardless of which class of neutral hydride was formed. For {(SBI)Zr} and {(Me2Si)2(C5H3) 2Zr} the resulting cations were crystallographically characterized where SBI stands for Me2Si(indenyl)2. [(SBI)Zr(mu-H) 3(AliBu2)2] + reacts with propene to make isotactic polypropene while the Me-substituted analogue [(SBI)Zr(mu-H)3(AlMe2)2] + is a catalyst for hydroalumination. These trihydride cations are shown to be dormant species in polymerization reactions. [(SBI)Zr(mu-H) 3(AliBu2)2] + is identified as the hydride observed by Babushkin and Brintzinger (Babushkin, D. E.; Brintzinger, H. H. Chem. Eur. J. 2007, 13, 5294) upon addition of Al iBu3 or HAliBu 2 to a mixture of (SBI)ZrCl2 and methylaluminoxane. |
Keywords/Search Tags: | SBI, Zirconocene, Hydrides |
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