Preparation, mechanism of formation, structure, and reactions of η-allyl complexes of ruthenium(II)

Reaction of either of two isomers of [Ru(CO)2Cl2(PMe2Ph)2] or either of two isomers of [{Ru(CO)Cl2(PMe2Ph)2}2] with SnBu3(C3H5) yields a single isomer of [Ru(CO)Cl(η-C3H5)(PMe2Ph)2]. A mechanism involving the intermediate formation of the five-co-ordinate species [Ru(CO)Cl2(PMe2Ph)2] and [Ru(CO)Cl(σ-C3H5)(PMe2Ph)2] is proposed for the reactions. Treatment of complexes [{Ru(Co)2Cl2L}2](L = phosphorus or arsenic ligand) with SnBu3(C3H5) yields the related complexes [Ru(CO)2Cl(η-C3H5)L], and the method can be extended to the preparation of 1-methylallyl and 2-methylallyl complexes. Simulation of the complex 1H n.m.r. spectra of [Ru(CO)2Cl(η-C3H5)(PMe2Ph)] and its AsMe2Ph analogue provides detailed information about the coupling between the protons in the allyl ligand. Treatment of [Ru(CO)2Cl(η-C3H5)(PMe2Ph)] with excess of PMe2Ph results in the formation of [Ru(CO)Cl(COC3H5)(PMe2Ph)3], which is very slowly converted in solution into [Ru(CO)Cl(η-C3H5)(PMe2Ph)2]: the key intermediate in the system appears to be [Ru(CO)2Cl(σ-C3H5)(PMe2Ph)2].