Enantioselective Transfer Hydrogenation of Ketones Catalyzed by a Manganese Complex Containing an Unsymmetrical Chiral PNP′ Tridentate Ligand

Abstract

Abstract Manganese complexes of the types [Mn(PNP′)(Br)(CO) 2 ] and [Mn(PNP′)(H)(CO) 2 ] containing a tridentate ligand with a planar chiral ferrocene and a centro chiral aliphatic unit were synthesized, characterized, and tested in the enantioselective transfer hydrogenations of 13 ketones. The catalytic reactions proceeded with conversions up to 96 % and ee values up to 86 %. The absolute configuration of all products was determined to be ( S ). Notably, the presence of dihydrogen (up to 20 bar) did not affect the reduction. On the basis of DFT calculations, preliminary mechanistic details including the origin of the ( S ) selectivity are presented. The molecular structure of [Mn(PNP′)(Br)(CO) 2 ] was studied by X‐ray diffraction.