Additive-Free Formic Acid Dehydrogenation Catalyzed by a Cobalt Complex

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.