Novel, recyclable supramolecular metal complexes for the synthesis of cyclic carbonates from epoxides and CO2 under solvent-free conditions

Abstract

A series of novel Zn, Cu, Fe supramolecular complexes were designed and synthesized. The structures of these compounds have been confirmed by IR, NMR, EA and X-ray crystallography. The complexes in combination with tetrabutylammonium bromide were studied as a binary catalyst system for CO2-fixation in the context of organic carbonate formation under solventless condition. The effects of various co-catalysts, co-catalyst concentration, reaction temperature, CO2 pressure, reaction time, various substituents on ligand and centre metal of complexes have been investigated systematically. The binary catalyst system also showed broad substrate scope of epoxide. The catalysts can be easily recovered and reused without significant loss of activity and selectivity. Comparison of different two-component dinuclear metal complexes catalysts reported by other scientists showed that the dinuclear metal complexes reported herein were competitive with most catalysts currently available. On the basis of the experimental results, the mechanism for the reaction was proposed.