Metal–ligand bifunctional catalysis for asymmetric hydrogenation

Chiral diphosphine/1,2-diamine–Ru(II) complexes catalyse the rapid, productive and enantioselective hydrogenation of simple ketones. The carbonyl-selective hydrogenation takes place via a non-classical metal–ligand bifunctional mechanism. The reduction of the C=O function occurs in the outer coordination sphere of an 18e trans -RuH 2 (diphosphine)(diamine) complex without interaction between the unsaturated moiety and the metallic centre. The Ru atom donates a hydride and the NH 2 ligand delivers a proton through a pericyclic six-membered transition state, directly giving an alcoholic product without metal alkoxide formation. The enantiofaces of prochiral ketones are differentiated on the chiral molecular surface of the saturated RuH 2 species. This asymmetric catalysis manifests the significance of ‘kinetic’ supramolecular chemistry.