Manganese(I)-Catalyzed Enantioselective Hydrogenation of Ketones Using a Defined Chiral PNP Pincer Ligand.

A new chiral manganese PNP pincer complex is described. The asymmetric hydrogenation of several prochiral ketones with molecular hydrogen in the presence of this complex proceeds under mild conditions (30-40 °C, 4 h, 30 bar H2 ). Besides high catalytic activity for aromatic substrates, aliphatic ketones are hydrogenated with remarkable selectivity (e.r. up to 92:8). DFT calculations support an outer sphere hydrogenation mechanism as well as the experimentally determined stereochemistry.