Mechanism of CO₂ reduction in carbonylation reaction promoted by ionic liquid additives: A computational and experimental study

The Ru-catalyzed carbonylation of alkenes with CO₂ as a C1 surrogate and imidazole chlorides as the promotor is investigated by a combination of computational and experimental study. The conversion rate of CO₂ to CO is positively correlated with the efficiency of both hydroesterification and hydroformylation, which is found facilitated in the presence of chloride additives with a decreasing order of BmimCl ∼ B3MimCl > BmmimCl ∼ LiCl. Taking the hydroesterification with MeOH as a representative example, BmimCl bearing C–H functionality at the C² site of the cation assists the reduction of CO₂ to CO as a hydrogen donor medium, with the anion and cation acting in a synergistic fashion. Subsequent insertion of CO₂ into the formed Ru–H bond with the assistance of chloride anion produces the Ru–COOH species, which ultimately accelerates the activation of CO₂.