Efficient transfer hydrogenation of ketones using molybdenum complexes by comprehensively verifying the auxiliary ligands.

Molybdenum complexes ligated with ,-dialkyl--(5,6,7,8-tetrahydroquinolin-8-yl)ethane-1,2-diamines and auxiliary ligands, providing various structural features, were developed: [NN/NNN]Mo(CO) (Mo1-Mo3), [NNN]Mo(CO)Br (Mo4-Mo5), [NN]Mo(CO)(η-CH)Br (Mo6) and [NNN/S]Mo(CO)(PPh) (Mo7-Mo8). All the complexes were highly active in the transfer hydrogenation (TH) of a model substrate (acetophenone), providing excellent yields of 1-phenylethanol. The structural variation in the ligand framework had a modest effect on the catalyst performance as compared to the changes in the auxiliary ligands Br, PPh and CO.