Conformationally rigid diphosphine arene–ruthenium(II) complexes as catalysts for transfer hydrogenation of ketones

Conformationally rigid [(η6-arene)Ru(PP)Cl]CF3SO3 (arene=C6H6 (1), p-MeC6H5CHMe2 (2), 1,3,5-Me3C6H3 (3), and Me6C6 (4); PP is 2-diphenylphosphino-5,6-dimethyl-7-phenyl-7-phosphabicyclo[2.2.1]hept-5-ene) compounds have been synthesized from [(η6-arene)RuCl2(DMPP)] (DMPP=3,4-dimethyl-1-phenylphosphole) and diphenylvinylphosphine (DPVP) in the presence of AgCF3SO3. The structures of 2, 3 and 4 were determined by X-ray crystallography. These complexes have been found to be quite effective catalysts for the transfer hydrogenation of ketones in 2-propanol in the presence of KOH.