Versatile and efficient manganese catalysts with a secondary amine-based PN-ligand for ketone and aldehyde hydrogenation.

Aiming to enhance the hydride-transfer ability of the active Mn-H species, molecular-level tuning of Mn-PN complexes was investigated by substituting an amino hydrogen with an electron-donating alkyl group. This strategy affords a new class of secondary amine-based Mn-PN catalysts, which significantly improves the catalytic efficiency in the hydrogenation of ketones and aldehydes compared to their primary amine-based counterparts. Herein, the complex with a methyl substituent, (o-Ph2PC6H4NHMe)Mn(CO)3Br, shows the best catalytic performance with a wide scope of substrates and mild reaction conditions.