Osmium(II)/R-pybox vs ruthenium(II)/R-pybox complexes in the catalytic asymmetric transfer hydrogenation of arylketones

•The efficiency of osmium complexes is superior to that of ruthenium complexes in the AHT reduction of ketones using M/pybox/pyridine catalysts.•The ruthenium and osmium catalysts shown herein are based on enantiopure N,N,N-ligands lacking the N-H functionality.•The osmium pybox complexes are promising species for the design of new highly productive and robust catalysts for the synthesis of chiral alcohols.•The nature of the achiral ligand has notable influence on the efficiency of these catalysts.