Hydrogenation of Carbon Dioxide to Methanol Catalyzed by Iron, Cobalt, and Manganese Cyclopentadienone Complexes: Mechanistic Insights and Computational Design.

Density functional theory study of the hydrogenation of carbon dioxide to methanol catalyzed by iron, cobalt, and manganese cyclopentadienone complexes reveals a self-promoted mechanism, which features a methanol- or water-molecule-assisted proton transfer for the cleavage of H . The total free energy barrier of the formation of methanol from CO and H catalyzed by Knölker's iron cyclopentadienone complex, [2,5-(SiMe ) -3,4-(CH ) (η -C COH)]Fe(CO) H, is 26.0 kcal mol in the methanol solvent. We also evaluated the catalytic activities of 8 other experimentally reported iron cyclopentadienone complexes and 37 iron, cobalt, and manganese cyclopentadienone complexes proposed in this study. In general, iron and manganese complexes have relatively higher catalytic activities. Among all calculated complexes, [2,5-(SiMe ) -3,4-CH CHSCH (η -C COH)]Fe(CO) H (1 ) is the most active one with a total free energy barrier of 25.1 kcal mol in the methanol solvent. Such a low barrier indicates that 1 is a very promising low-cost and high efficiency catalyst for the conversion of CO and H to methanol under mild conditions.