Bond Activation by Metal-Ligand Cooperation: Design of “Green” Catalytic Reactions Based on Aromatization-Dearomatization of Pincer Complexes

Abstract

We have developed a new mode of bifunctional catalysis based on metal–ligand cooperation, involving aromatization–dearomatization of pyridine- and acridine-derived pincer complexes. This type of metal–ligand cooperation is involved in the recently discovered environmentally benign reactions of alcohols, catalyzed by PNP and PNN pincer complexes of ruthenium, including: (a) dehydrogenation of secondary alcohols to ketones, (b) dehydrogenative coupling of primary alcohols to form esters and H2, (c) unprecedented amide synthesis: catalytic coupling of amines with alcohols, with liberation of H2, (d) direct synthesis of imines from alcohols and amines with H2 liberation, (e) direct conversion of alcohols to acetals with H2 liberation, (f) selective synthesis of primary amines from alcohols and ammonia, and (g) hydrogenation of esters to alcohols under mild conditions. These reactions are very efficient, proceed under neutral conditions, and produce no waste.