Hydrogen-Transfer Catalysis with Pincer-Aryl Ruthenium(II) Complexes

The transfer-hydrogenation of ketones with iPrOH in the presence of a base is catalyzed by pincer-aryl ruthenium(II) complexes (see scheme, R3=NMe2 or PPh2, X=Cl or OSO2CF3). Conversions of 90 – 98 % are achieved without removal of the acetone by-product. The structural unit [Ru(pincer-aryl)PPh3] is stable under the reaction conditions and is preserved during the catalytic cycle. An anionic Ruii hydrido complex was identified as the resting state of the catalyst at the onset of the reaction.