Bioinspired Design and Computational Prediction of Iron Complexes with Pendant Amines for the Production of Methanol from CO2 and H2

Inspired by the active site structure of [FeFe]-hydrogenase, we built a series of iron dicarbonyl diphosphine complexes with pendant amines and predicted their potentials to catalyze the hydrogenation of CO2, to methanol using density functional theory. Among the proposed iron complexes, [((P2N2H)-N-tBu-H-tBu)FeH(CO)(2)(COOH)](+)(5(COOH)) is the most active one with a total free energy barrier of 23.7 kcal/mol. Such a low barrier indicates that 5(COOH) is a very promising low-cost catalyst for high-efficiency conversion of CO2, and H-2 to methanol under mild conditions. For comparison, we also examined Bullock's Cp iron diphosphine complex with pendant amines, [(p(2)(tBu)N(2)(tBu)H)FeHCpC5F4N](+) (5(Cp-C5F4N)), as a catalyst for hydrogenation of CO2, to methanol and obtained a total free energy barrier of 27.6 kcal/mol, which indicates that 5(Cp-C5F4N) could also catalyze the conversion of CO2, and H-2 to methanol but has a much lower efficiency than our newly designed iron complexes.