Cycloaddition of carbon dioxide and epoxides catalyzed by rare earth metal complexes bearing a Trost ligand

Abstract

A series of rare earth metal complexes (Sm (1), Eu (2), Y (3), Yb (4), and Lu (5)) based on Trost ligands were synthesized and well characterized, and catalyzed the cycloaddition of carbon dioxide and epoxides successfully. The combination of 1 mol% Sm-based complex 1 with 2 mol% tetrabutylammonium bromide (TBAB) was proved to be the optimal catalyst system for the formation of the monosubstituted cyclic carbonate at 70 °C under the atmospheric pressure. While for the more challenging disubstituted epoxides, the adduct cyclic carbonates were successfully obtained when the pressure of CO₂ was elevated to 0.7 MPa.