Ruthenium(II) carbonyl complexes bearing CCC-pincer bis-(carbene) ligands: synthesis, structures and activities toward recycle transfer hydrogenation reactions

A new series of ruthenium(II) carbonyl complexes with benzene-based CCC-pincer bis-(carbene) ligands, [((CCCR)-C-R)Ru(CO)(2)(X)](0/+) and [((CCCR)-C-R)Ru(CO)(NN)](+) ((CCCR)-C-R = 2,6-bis-(1-alkylimidazolylidene) benzene, R = Me or Bu-n; X = I, Br, CH3CN, or 6-(aminomethyl)pyridine (ampy); NN = 2 center dot CH3CN, or chelating ampy or bipyridine), was synthesized and fully characterized. X-Ray structure determinations revealed that these eight complexes have pseudo-octahedral configurations around the ruthenium center with the pincer ligand occupying three meridional sites. These complexes prove to be efficient precatalysts demonstrating very good activity and reusability for the transfer hydrogenation of ketones.