Pincer chromium(II)-catalyzed hydrogenation of CO2 and bicarbonate to formate.

We report here the catalytic hydrogenation of carbon dioxide to formate using a Cr(II) pincer complex. The complex CrCl2(PNP) C-1 {PNP = N,N-bis(diphenylphosphinoethyl)amine} in combination with NaHBEt3 in the presence of NaOH in a THF : H2O mixture yielded formate after 48 h with a TON of up to 8700. The complex C-1 was also found to be an active catalyst for the hydrogenation of sodium bicarbonate, furnishing formate with up to 62% yield. Stoichiometric experiments were carried out based on which a probable mechanism involving metal-ligand cooperation is proposed.