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Kinetic and Density Functional Studies on Alkyl-Carbene Elimination from PdII Heterocyclic Carbene Complexes: A New Type of Reductive Elimination with Clear Implications for Catalysis

Citation

McGuinness, DS and Saendig, NS and Yates, BF and Cavell, KJ, Kinetic and Density Functional Studies on Alkyl-Carbene Elimination from PdII Heterocyclic Carbene Complexes: A New Type of Reductive Elimination with Clear Implications for Catalysis, Journal of the American Chemical Society, 123, (17) pp. 4029-4040. ISSN 0002-7863 (2001) [Refereed Article]

DOI: doi:10.1021/ja003861g

Abstract

A number of new methyl-Pd II complexes of heterocyclic carbenes of the form [PdMe(tmiy)L 2]BF 4 have been prepared, and their reaction behavior has been studied (tmiy = 1,3,4,5-tetramethylimidazolin-2-ylidene, L = cyclooctadiene (8), methyldiphenylphosphine (9), triphenyl phosphite (10), triphenylphosphine (11)). In common with other hydrocarbyl-M carbene complexes (M = Pd, Ni) the complexes are predisposed to a facile decomposition process. A detailed mechanism for the process and of the decomposition pathway followed is presented herein. All complexes decompose with first-order kinetics to yield 1,2,3,4,5-pentamethylimidazolium tetrafluoroborate and Pd 0 species. The kinetic investigations combined with density functional studies show that the complexes decompose via a mechanism of concerted reductive elimination of the methyl group and carbene. The reaction represents a new type of reductive elimination from transition metals and also represents a low-energy pathway to catalyst deactivation for catalysts based on heterocyclic carbenes. The theoretical studies indicate extensive involvement of the p(π) orbital on the carbene carbon in the transition structure. Methods of stabilizing catalysts based on heterocyclic carbene complexes are suggested, and the possibility of involvement of carbene species during catalysis in ionic liquids is discussed.

Item Details

Item Type:Refereed Article
Research Division:Chemical Sciences
Research Group:Other Chemical Sciences
Research Field:Organometallic Chemistry
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Chemical Sciences
Author:McGuinness, DS (Dr David McGuinness)
Author:Yates, BF (Professor Brian Yates)
Author:Cavell, KJ (Professor Kingsley Cavell)
ID Code:22478
Year Published:2001
Web of Science® Times Cited:201
Deposited By:Chemistry
Deposited On:2001-08-01
Last Modified:2007-11-08
Downloads:0

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