trans- and cis-Ru(II) aminophosphine complexes: Syntheses, X-ray structures and catalytic activity in transfer hydrogenation of acetophenone derivatives

The ability of transition metal catalysts to add or remove hydrogen from organic substrates by transfer hydrogenation process is a valuable synthetic tool. For this aim, a novel Ru(II) complex with the P-N ligand [(Ph2P)(2)NCH2-C4H3S] derived from thiophene-2-methylamine was synthesized starting with the complex [Ru(eta(6)-p-cymene)(mu-Cl)Cl](2) and isolated in two isomeric forms: trans- and cis[Ru((PPh2)(2)NCH2-C4H3S)(2)Cl-2], 2 and 3, respectively. The structures of both isomers were also determined by single crystal X-ray diffraction. The cis-isomer 3 can be isolated from the solution of major trans-isomer 2 as yellow crystals. However, upon dissolution 3 is rapidly converted to the trans-isomer 2. The new ruthenium(II) complex provides high catalytic activity in the transfer hydrogenation of acetophenone derivatives to 1-phenylethanol derivatives in the presence of 2-propanol as the hydrogen source. This transfer hydrogenation is characterized by low reversibility under the experimental conditions. (C) 2010 Elsevier B.V. All rights reserved.