Clean methods for reduction of carboxylic acid derivatives are highly desirable for fine chemical and pharmaceutical industries. The transformation of carbon dioxide is of great significance for sustainable development. Several transition metal catalysts have been developed for the hydrogenations of carboxylic esters and amides, as well as carbon dioxide, producing alcohols, amines and formic acids.

n Ru(II)-PNNN (tetradentate bipyridine) complexes catalyzed hydrogenation of carboxylic esters and lactones to alcohols

n Ir(III)-PCP (tridentate pincer complex) catalyzed hydrogenation of amides to amines

n Mn(I)-PNN (pyridine-amino-phospine) complexes catalyzed hydrogenation of nitriles to imines and amines

n Ir(III)-PNP (imine-diphosphine) complexes catalyzed hydrogenation of carbon dioxide to formates

n Ru(II)-PNNN (tetradentate bipyridine) complexes catalyzed hydrogenation of carbon dioxide to formamides and methanol