Dinuclear Silver Complexes for Solvent-Free Catalytic Synthesis of Cyclic Carbonates from Epoxides and CO2 at Ambient Temperature and Pressure

Abstract

A well structure-defined dinuclear silver complex [Ag2(PDP)]OTf, where HPDP—bispyridylpyrrole ligand, OTf−—triflato, was used as catalyst for coupling of CO2 with epoxides to generate exclusive cyclic carbonates. Yield up to 87% was obtained for various substrates at a low loading of 0.1 mol%, at ambient temperature and pressure under solvent-free condition. The catalytic reusability of 1·OTf was also studied. Although coupling reaction of CO2 with epoxides can be catalyzed by dinuclear silver complexes with low catalyst loading at ambient temperature and pressure, the experiment of reusability of catalyst displays the dinuclear silver complex is decomposed due to the excess Br− in co-catalyst TBAB. The formed silver triphenylphosphine complex or inorganic silver materials provide real catalytic reactivity to the coupling reaction.