Mechanistic Insights into Ruthenium-Catalyzed Production of H2 and CO2 from Methanol and Water: A DFT Study

A density functional theory study of the reaction mechanism of the production of H-2 and CO2 from methanol and water catalyzed by an aliphatic PNP pincer ruthenium complex, (PNP)Ru(H)CO, reveals three interrelated catalytic cycles for the release of three H-2 molecules: the dehydrogenation of methanol to formaldehyde, the coupling of formaldehyde and hydroxide for the formation of formic acid, and the dehydrogenation of formic acid. The formation of all three H-2 molecules undergoes the same self-promoted mechanism that features a methanol or a water molecule acting as a bridge for the transfer of a ligand proton to the metal hydride in a key intermediate, trans-(HPNP)Ru(H)(2)CO.