Base-Free Hydrogenation of Carbon Dioxide to Methyl Formate with a Molecular Ruthenium-Phosphine Catalyst

Herein, a molecular ruthenium-phosphine catalyst system for the effective base-free methyl formate production from carbon dioxide is described. In detail, the novel [Ru(N-triphos(Cy))(tmm)] complex, bearing sterically demanding cyclohexyl groups in the triphos-ligand structure, enabled in combination with the Lewis acid Al(OTf)(3) the selective transformation of carbon dioxide to methyl formate with unprecedented activity. From a mechanistic perspective, in the initial step formic acid is formed, undergoing a consecutive Lewis acid promoted esterification with methanol to methyl formate. This selective transformation with carbon dioxide paves the way to versatile processes for important C-1 building blocks.