Metal Complexes of an Ionic Liquid-Derived Carbene
A range of metal carbene complexes containing the ionic liquid-derived N-heterocyclic carbene (NHC) 1-nbutyl-3-methylimidazol-2-ylidene (IBuMe, 1) have been prepared by (i) direct ligand substitution using the free NHC ([Mo(CO)5(IBuMe)] 2), (ii) transmetallation using the silver salt [AgCl(IBuMe)] (3) ([RhCl(NBD)(IBuMe)] (4) and [IrCl(COD)(IBuMe)] (5), NBD = 2,5-norbornadiene, COD = 1,5-cyclooctadiene) and (iii) direct reaction of a metal acetate with the hydrochloride salt of 1 (trans-[PdCl2(IBuMe)] (6)). The dicarbonyl cis-[RhCl(CO)2(IBuMe)] (7) has been prepared by diene substitution under a carbon monoxide atmosphere. The molecular structures of 2, 4, 5 and 6 are reported and the sigma donation and steric properties of 1 are discussed relative to those of common imidazol-2-ylidene ligands.