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 I 3 Cu II 2 (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. CO 2 and epoxides were transformed into cyclic carbonates at ambient pressure and room temperature with high yields using Cu I 3 Cu II 2 (OH)pz 6 ·CH 3 CN .