Conversion of uncharged methyl complexes of ruthenium(II) into a cationic acyl complex: a mechanistic study

Abstract

Spectroscopic studies of the reactions of methyl complexes [Ru(CO)₂(Me)X(PMe₂Ph)₂][X = Cl, (1a); X = I, (1b)] with Me₃CNC have revealed that the end-product, [Ru(CO)(CNCMe₃)₂(COMe)(PMe₂Ph)₂]⁺(2), is formed via two isomers of the complexes [Ru(CO)(CNCMe₃)(COMe)X-(PMe₂Ph)₂][X = Cl, (3a) and (4a); X = I, (3b) and (4b)]. Formation of the kinetically favoured isomers (3a) and (3b), from (1a) and (1b) respectively, is very rapid, while the relative rates of the isomerization and the further reaction with Me₃CNC to yield (2) vary with the solvent and the halide ion X^–. Two alternative mechanisms for the isomerization, involving dissociation of the isonitrile or the halide ligand, are discussed.