Five- and six-coordinate ruthenium(II) complexes containing 2-Ph2PC6H4CH=NtBu and 2-Ph2PC6H4CH2NHtBu as chelate ligands:: Synthesis, characterization, and catalytic activity in transfer hydrogenation of ketones

Five- and six-coordinate ruthenium(II) complexes containing imino- and aminophosphines have been prepared by ligand exchange processes. Thus, reactions of [RuCl2(PPh3)(3)] and [RuCl2(DMSO)(4)] with 2-Ph2PC6H4CH=(NBu)-Bu-t (a) lead to [RuCl2(kappa (2)-P,V-2-Ph2PC6H4CH=(NBu)-Bu-t)(PPh3)] (I a) and trans-[RuCl2(kappa (2)-P,N-2-Ph2PC6H4CH=(NBu)-Bu-t)(DMSO)(2)] (2a), respectively. Similarly, reactions with 2-(Ph2PC6H4CH2NHBu)-Bu-t (b) afford complexes [RuCl2(kappa (2) -P,N-2-(Ph2PC6H4CH2NHBu)-Bu-t)(PPh3)] (5b) and [RuCl2(kappa (2)-P,N-2-(Ph2PC6H4CH2NHBu)-Bu-t)(DMSO)] (6b) in good yield. The crystal structures of la and 5b have been determined by X-ray diffraction. Compound 2a, containing two labile DMSO ligands, has been used as a precursor to synthesize the derivatives [RuCl2(kappa (2)-P,N-2-Ph2PC6H4CH=(NBu)-Bu-t)L] [L = PPh3 (1a); PPh2Me (3a); PMe2Ph (4a)]. Complexes la, 2a, 5b, and 6b are active in catalytic transfer hydrogenation of aryl-alkyl and dialkyl ketones in propan-2-ol. The five-coordinate complexes la, 5b, and 6b show higher catalytic activity than the octahedral complex 2a. Complexes la and 5b are more efficient catalysts than the precursor complex [RuCl2(PPh3)(3)]. For the best catalyst, la, yields up to 91% were obtained and turnover frequencies may be as high as 41 400 h(-1).