Novel Coordinatively Unsaturated Bimetallic Complexes, [(η5-C5Me5)Ru(μ2-iPrNC(Me)NiPr)Ru(η5-C5Me5)]+: A Bridging Amidinate Ligand Perpendicular to the Metal−Metal Axis Effectively Stabilizes the Highly Reactive Cationic Diruthenium Species

Coordinatively unsaturated diruthenium complexes, [(η5-C5Me5)Ru(μ2-iPrNC(Me)NiPr)Ru(η5-C5Me5)]+, of which crystallography revealed structures bearing a bridging amidinate ligand perpendicular to the Ru−Ru axis, were synthesized by anion exchange of [(η5-C3Me5(Ru(μ2-iPrNC(Me)NiPr)Ru(η5-C5Me5)]+ Br- by weakly coordinating anions. Variable-temperature NMR showed rapid motion of the bridging amidinate ligand. The coordinatively unsaturated nature of the cationic complexes provides their high reactivity toward a series of two electron donor ligands. Oxidative addition of molecular hydrogen occurred to give [(η5-C5Me5)Ru(μ2-iPrNC(Me)NiPr)(μ-H)Ru(η5-C5Me5)(H)]+, which was isolated and characterized.