Additive-Free Formic Acid Dehydrogenation Catalyzed by a Cobalt Complex

Abstract : The reversible storage of hydrogen through the intermediate formation of formic acid (FA) is a promising solution to its safe transport and distribution. However, the common necessity of using bases or additives in the catalytic dehydrogenation of FA is a limitation. In this context, two new cobalt complexes (1 and 2) were synthesized with a pincer PP(NH)P ligand containing a phosphoramine moiety. Their reaction with an excess FA yields a cobalt(I) hydride complex (3). We report here the unprecedented catalytic activity of 3 in the dehydrogenation of FA, with a turnover frequency (TOF) of 67 min–1 measured in the first minute and a turnover number (TON) of 454, without the need for bases or additives. A mechanistic study reveals the existence of ligand–metal cooperativity with intermolecular hydrogen bonding, also influenced by the concentration of formic acid.