An efficient mixed-valence copper pyrazolate catalyst for the conversion of carbon dioxide and epoxides into cyclic carbonates.

In this paper, a cyclic (Cu I pz) 3 ·CH 3 CN (1) precursor and a mixed-valence pentanuclear complex Cu I3 CuII2(OH)pz 6 ·CH 3 CN (2) have been synthesized and structurally characterized by single-crystal X-ray diffraction, where pzH = 4-chloro-3,5-diphenylpyrazole. The excellent catalytic activity of 2 has been demonstrated in the chemical fixation of CO 2 into value-added cyclic carbonates, which can be carried out at ambient pressure and room temperature along with ultra-high yield and perfect steric hindrance tolerance. Based on density functional theory (DFT) calculations and comparison with the catalytic performance of 1, it is proposed that the coordinatively unsaturated Cu II atoms of 2 are probably the active sites for this catalytic reaction.