Discovery of Environmentally Benign Catalytic Reactions of Alcohols Catalyzed by Pyridine-Based Pincer Ru Complexes, Based on Metal-Ligand Cooperation

We have developed a new mode of metal-ligand cooperation, based on aromatization-dearomatization of pyridine-based pincer-type ligands, and have demonstrated it in the activation of H-2 and C-H bonds by PNP Ir complexes. This type of metal-ligand cooperation plays a key role 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 H-2 (c) hydrogenation of esters to alcohols under mild conditions (d) unprecedented amide synthesis: catalytic coupling of amines with alcohols, with liberation of H-2. Ligand modification in the latter reaction has led to unprecedented synthesis of imines with H-2 liberation. These reactions are very efficient, proceed under neutral conditions and produce no waste.