Heterogeneous and homogeneous asymmetric electrocatalytic hydrogenation with rhodium(III) complexes containing chiral polypyridyl ligands

Abstract

The electrocatalytic hydrogenation in aqueous electrolyte of acetophenone and 2-butanone with [Rh(L)2Cl2]+ complexes (L is a chiral 2,2′-bipyridine or a 1,10-phenanthroline) has been investigated in homogeneous media or at carbon electrodes coated with thin polymer films prepared by oxidative electropolymerization of a rhodium complex containing a pyrrole-substituted chiral 2,2′-bipyridine ligand. The latter device gave the best results in terms of catalytic efficiency, turnover number (up to 4750) and asymmetric induction (up to 20% ee). From the viewpoint of catalytic efficiency and asymmetric induction, the electrocatalytic system compares well with asymmetric transfer hydrogenation catalyzed by rhodium complexes containing the same ligands.