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.