Hydrogenation of CO2, Hydrogenocarbonate, and Carbonate to Formate in Water using Phosphine Free Bifunctional Iron Complexes

The development of efficient and low-cost catalytic systems is important for the replacement of the robust noble metal complexes. A highly efficient, stable, phosphine-free, and easy-to-synthesize iron catalyst system for the reduction of CO2, hydrogenocarbonate, and carbonate in pure water is reported. In the presence of the bifunctional cyclopentadienone iron tricarbonyl Fe4a–d, the hydrogenation of carbonic derivatives proceeds in good yields with good catalyst productivity. Turnover numbers (TON) of up to 3343, 4234, and 40 for the hydrogenation of CO2, hydrogenocarbonate, and carbonate, respectively, to formate in pure water were achieved. For the CO2 hydrogenation, a base was required, and triethanolamine emerged as the best one. DFT calculations rationalized the mechanism as well as the better performance of triethanolamine as a base.