Bifunctional Rare-Earth Metal Catalysts for Conversion of CO2 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 CO2. Lanthanum complex 1(La) was most active, converting terminal epoxides into the cyclic carbonates in moderate to excellent yields at 40 degrees C in the presence of 1 bar CO2. The catalyst was also recycled five runs without loss of catalytic activity. The kinetics of the cycloaddition of CO2 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.

Automated summary

A series of bifunctional rare-earth metal complexes with zwitterionic amino-bis(phenolato) ligands were synthesized and used as catalysts for the synthesis of cyclic carbonates. Lanthanum complex 1(La) showed the highest catalytic activity and could be recycled without loss of activity. The activation energy for the cycloaddition reaction was determined to be 8.29 +/- 0.68 kcal/mol using complex 1(La) as the catalyst.