Bifunctional Rare‐Earth Metal Catalysts for Conversion of CO 2 and Epoxides into Cyclic Carbonates

A series of bifunctional rare‐earth metal complexes bearing zwitterionic amino‐bis(phenolato) ligands were synthesized and structurally characterized. These complexes were applied as catalysts for the synthesis of cyclic carbonates from epoxides and CO 2 . Lanthanum complex 1 La was most active, converting terminal epoxides into the cyclic carbonates in moderate to excellent yields at 40 °C in the presence of 1 bar CO 2 . The catalyst was also recycled five runs without loss of catalytic activity. The kinetics of the cycloaddition of CO 2 and epichlorohydrin (ECH) catalyzed by complex 1 La were investigated. According to the Arrhenius equation, the activation barrier for cyclic carbonate formation is determined to be 8.29±0.68 kcal/mol.