Isolable yet highly reactive cationic organoruthenium(II) amidinates, [Ru(η6-C6R6)(η-amidinate)] +X-, showing signs of coordinative unsaturation: Isoelectronic complexes of Ru(η5-C5Me5)(η-amidinate)

The coordinatively unsaturated ruthenium(II) complexes [Ru(η6-C6R6)(η-amidinate)]+X− (R = H, Me, X = TFPB, PF6), being isoelectronic with Ru(η5-C5Me5)(η-amidinate), have been isolated and characterized by spectroscopy and crystallography. A weak π-coordination of the amidinate ligands in the solid state was observed by X-ray crystallography. DFT calculations also suggest that such a coordination mode contributes to the stabilization of these complexes. These complexes behave as highly reactive transition metal Lewis acids in the reactions with various two-electron donor ligands.