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

Abstract

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)2NCH2–C4H3S] derived from thiophene-2-methylamine was synthesized starting with the complex [Ru(η6-p-cymene)(μ-Cl)Cl]2 and isolated in two isomeric forms: trans- and cis-[Ru((PPh2)2NCH2–C4H3S)2Cl2], 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.