Cobalt(II)-Catalyzed Transfer Hydrogenation of Simple Alkenes

Several cobalt(II) complexes supported by tetradentate aminobenzimidazole (N4) ligands and a tridentate nitrogen (N3) ligand have been prepared and characterized. X-ray crystallographic analysis indicates that the cobalt complex of BPMB (BPMB=1,2-bis((S)-2-(1-methyl-1H-benzo[d]imidazol-2-yl) pyrrolidin-1-yl)ethane) ligand shows a distorted octahedral configuration. These cobalt(II) complexes can catalyze the transfer hydrogenation reaction of simple olefins with ammonia borane as a hydrogen source, and a variety of terminal olefins can be reduced to corresponding alkanes in good to excellent yields under mild reaction conditions. Note that Co-N3 complex provides an inferior outcome than those of Co-N4 complexes.