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Design and Theoretical Study of Nickel Catalysts for Syndiotactic Polyolefins

Design and Theoretical Study of Nickel Catalysts for Syndiotactic Polyolefins A nickel catalyst was modeled with ligand L2, [NH = CH—CH = CH—O]−, which should have potential use as a syndiotactic polyolefin catalyst, and the reaction mechanism was studied by theoretical calculations using the density functional method at the B3LYP/ LANL2MB level. The mechanism involves the formation of the intermediate [NiL2Me]+, in which the metal occupies a T‐shaped geometry. This intermediate has two possible structures with the methyl group trans either to the oxygen or to the nitrogen atom of L2. The results show that both structures can lead to the desired product via similar reaction paths, A and B. Thus, the polymerization could be considered as taking place either with the alkyl group occupying the position trans to the Ni—O or trans to the Ni—N bond in the catalyst. The polymerization process thus favors the catalysis of syndiotactic polyolefins. The syndiotactic synthesis effects could also be enhanced by variations in the ligand sub‐stituents. From energy considerations, we can conclude that it is more favorable for the methyl group to occupy the trans‐O position to form a complex than to occupy the trans‐N position. From bond length considerations, it is also more favoured for ethene to occupy the trans‐O position than to occupy the trans‐N position. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Chinese Journal of Chemistry Wiley

Design and Theoretical Study of Nickel Catalysts for Syndiotactic Polyolefins

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References (14)

Publisher
Wiley
Copyright
Copyright © 2003 Wiley Subscription Services, Inc., A Wiley Company
ISSN
1001-604X
eISSN
1614-7065
DOI
10.1002/cjoc.20030210502
Publisher site
See Article on Publisher Site

Abstract

A nickel catalyst was modeled with ligand L2, [NH = CH—CH = CH—O]−, which should have potential use as a syndiotactic polyolefin catalyst, and the reaction mechanism was studied by theoretical calculations using the density functional method at the B3LYP/ LANL2MB level. The mechanism involves the formation of the intermediate [NiL2Me]+, in which the metal occupies a T‐shaped geometry. This intermediate has two possible structures with the methyl group trans either to the oxygen or to the nitrogen atom of L2. The results show that both structures can lead to the desired product via similar reaction paths, A and B. Thus, the polymerization could be considered as taking place either with the alkyl group occupying the position trans to the Ni—O or trans to the Ni—N bond in the catalyst. The polymerization process thus favors the catalysis of syndiotactic polyolefins. The syndiotactic synthesis effects could also be enhanced by variations in the ligand sub‐stituents. From energy considerations, we can conclude that it is more favorable for the methyl group to occupy the trans‐O position to form a complex than to occupy the trans‐N position. From bond length considerations, it is also more favoured for ethene to occupy the trans‐O position than to occupy the trans‐N position.

Journal

Chinese Journal of Chemistry – Wiley

Published: May 1, 2003

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