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Oxidative addition of 2-substituted azolium salts to Group-10 metal zero complexes — A DFT study

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Graham, DC and Cavell, KJ and Yates, BF (2007) Oxidative addition of 2-substituted azolium salts to Group-10 metal zero complexes — A DFT study. Dalton Transactions, 41. pp. 4650-4658. ISSN 1477-9226

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Abstract

Generation of N-heterocyclic carbene (NHC) complexes [(dmpe)M(azol-2-ylidene)R] via the oxidative
addition of a series of 2-substituted azolium salts to Group-10 zerovalent metal complexes has been
investigated using density functional theory (2-R = H, Me, Ph; Azole = imidazole, thiazole,
oxazole; M= Ni, Pd, Pt). Overall, platinum-based pathways result in the greatest enthalpies of reaction,
but due to the reactive nature of Group-10 metals bearing the 1,2-bis(dimethylphosphino)ethane
(dmpe) chelate, nickel and palladium species also have little trouble proceeding to stable products in the
absence of a significant barrier. Imidazolium salts were found to be the most vulnerable to oxidative
addition due to their low stabilisation energies when compared to the oxazolium and thiazolium
species. Activation barriers show the general trend of phenyl > methyl > hydrido with regard to the
azole 2-substituent, with no observed barrier for all but one of the 2-hydrido cases. Minimal barriers
were found to exist in a number of cases for activation of a C(2)–CH3 bond suggesting that synthesis of
alkyl–carbene complexes may be possible via this route under certain conditions, and therefore ionic
liquids based on these substituted azolium salts may be active participants in catalytic reactions.

Item Type: Article
Journal or Publication Title: Dalton Transactions
Page Range: pp. 4650-4658
ISSN: 1477-9226
Identification Number - DOI: 10.1039/b709914b
Date Deposited: 07 Mar 2008 00:21
Last Modified: 18 Nov 2014 03:31
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