Isolable yet highly reactive cationic organoruthenium(II) amidinates, [Ru(eta(6)-C6R6)(eta-amidinate)]X-+(-), showing signs of coordinative unsaturation: Isoelectronic complexes of Ru(eta(5)-C5Me5)(eta-amidinate)

The coordinatively unsaturated ruthenium(II) complexes [Ru(eta (6)-C6R6(eta -amidinate)]X-+(-) (R = H, Me, X = TFPB, PF6), being isoelectronic with Ru (eta (5)-C5Me5)(eta -amidinate), have been isolated and characterized by sp ectroscopy and crystallography. A weak pi -coordination of the amidinate li gands in the solid state was observed by X-ray crystallography. DFT calcula tions also suggest that such a coordination mode contributes to the stabili zation of these complexes. These complexes behave as highly reactive transi tion metal Lewis acids in the reactions with various two-electron donor lig ands.