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Catalyst Site Epimerization during the Kinetic Resolution of Chiral α-Olefins by Polymerization

Min, Endy Y.-J. and Byers, Jeffery A. and Bercaw, John E. (2008) Catalyst Site Epimerization during the Kinetic Resolution of Chiral α-Olefins by Polymerization. Organometallics, 27 (10). pp. 2179-2188. ISSN 0276-7333. doi:10.1021/om700778e.

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A new enantiopure C1-symmetric olefin polymerization precatalyst, (1,2-SiMe_2)_2{η^5-C_5H_2-4-((S)-CHEtCMe_3)}{η^5-C_5H-3,5-(CHMe_2)_2}ZrCl_2, (S)-2, was synthesized, and its use for the kinetic resolution of 3-methyl-substituted racemic α-olefins was investigated. Upon activation with methyl aluminoxane (MAO), selectivity factors for most olefins were greater when (S)-2 was used as the catalyst as compared to its previously reported methylneopentyl analogue, (1,2-SiMe_2)_2{η^5-C_5H_2-4-((S)-CHMeCCMe_3)}{η^5-C_5H-3,5-(CHMe_2)_2}ZrCl_2, (S)-1. Pentad analysis of polypropylene produced by the two catalysts at various propylene concentrations indicates that (S)-2 undergoes more efficient site epimerization (polymeryl chain swinging prior to subsequent monomer enchainment) at intermediate propylene concentrations compared to (S)-1. At high and low propylene concentrations, however, the two catalysts behave similarly. On the other hand, polymerization of 3,5,5-trimethyl-1-hexene at different olefin concentrations and temperatures illustrated that selectivity differences between the two catalysts are likely not a consequence of inefficient site epimerization for (S)-1.

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Additional Information:© 2008 American Chemical Society. Received 31 July 2007. Published online 25 April 2008. Published in print 1 May 2008. This work was supported by USDOE Office of Basic Energy Sciences (Grant No. DE-FG03-85ER13431) and the National Science Foundation (Grant No. CHE-0131180). We thank Professors Steve Miller and Jay Labinger for help with the statistical modeling of polymerizations of propylene with catalysts (S)-1 and (S)-2. We would also like to thank Dr. Larry Henling and Dr. Mike Day for their work in solving the X-ray crystal structure of (S)-2 and Steven Baldwin for help with the characterization of some of the compounds.
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Department of Energy (DOE)DE-FG03-85ER13431
Issue or Number:10
Record Number:CaltechAUTHORS:20170308-131107147
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Official Citation:Catalyst Site Epimerization during the Kinetic Resolution of Chiral α-Olefins by Polymerization Endy Y.-J. Min, Jeffery A. Byers, and John E. Bercaw Organometallics 2008 27 (10), 2179-2188 DOI: 10.1021/om700778e
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:74906
Deposited By: Ruth Sustaita
Deposited On:08 Mar 2017 22:20
Last Modified:15 Nov 2021 16:29

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