Transfer Hydrogenation of Carbonyl Groups, Imines and N-Heterocycles Catalyzed by Simple, Bipyridine-Based MnI Complexes

Utilization of hydroxy-substituted bipyridine ligands in transition metal catalysis mimicking [Fe]-hydrogenase has been shown to be a promising approach in developing new catalysts for hydrogenation. For example, Mn-I complexes with 6,6'-dihydroxy-2,2'-bipyridine ligand have been previously shown to be active catalysts for CO2 hydrogenation. In this work, simple bipyridine-based Mn catalysts were developed that act as active catalysts for transfer hydrogenation of ketones, aldehydes and imines. For the first time, Mn-catalyzed transfer hydrogenation of N-heterocycles was reported. The highest catalytic activity among complexes with variously substituted ligands was observed for the complex bearing two OH groups in bipyridine. Deuterium labeling experiments suggest a monohydride pathway.