The oxidative addition of 1,3-dimethylimidazolium to a model Wilkinson's catalyst (RhCl(PH3)3) has been studied with density functional calculations (B3LYP). According to our free energy calculations, the octahedral rhodium carbene hydride product forms from initial predissociation of a phosphine molecule to subsequently form a 5 ligand intermediate; however, results indicate that a six ligand, associative route with a concerted three-centred transition structure may also be competitive. Exchange of the phosphine molecule on the metal centre with trimethylphosphine had a significant effect in lowering the barrier to oxidative addition and decreasing the endothermicity of the reaction. Solvation was found to have a moderate effect on the overall reaction. Bulk solvent calculations reflected a relative stabilisation of reactants for both pathways, resulting in an endothermic overall reaction. A study of alternative azolium salts revealed the saturated 1,3-dimethy1-4,5-dihydroimidazolium resulted in little change to the reaction geometries or energies, while the use of 3-methylthiazolium salt significantly reduced the barrier to addition and increased the exothermicity of the reaction considerably.

Item Type:	Refereed Article
Research Division:	Chemical Sciences
Research Group:	Inorganic chemistry
Research Field:	Organometallic chemistry
Objective Division:	Expanding Knowledge
Objective Group:	Expanding knowledge
Objective Field:	Expanding knowledge in the chemical sciences
UTAS Author:	Hawkes, KJ (Dr Kirsty Hawkes)
UTAS Author:	McGuinness, DS (Dr David McGuinness)
UTAS Author:	Cavell, KJ (Professor Kingsley Cavell)
UTAS Author:	Yates, BF (Professor Brian Yates)
ID Code:	31986
Year Published:	2004
Web of Science® Times Cited:	21
Deposited By:	Chemistry
Deposited On:	2004-08-01
Last Modified:	2011-09-30
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