Dong-Hui Lan, Chak-Tong Au and Shuang-Feng Yin Pages 35 - 42 ( 8 )
Bi-functional Zn-EDTA complexes that are non-toxic and stable can be conveniently synthesized using water as solvent. The complexes are efficient heterogeneous catalysts for the synthesis of cyclic carbonates from CO2 and epoxides without the need of a co-catalyst or solvent. Among the complexes, ZnBr2- EDTA-2Na is the most effective, showing a turnover frequency of 96.9 h-1 (cat./PO = 0.25 mol%, 150 °C, 2.25 MPa, 4 h). The catalyst can be easily recovered and reused without significant loss of activity across a test of five runs. We studied the effects of reaction temperature, pressure, and time as well as catalyst amount on the reaction. It was found that the synergetic actions of metal centers (Lewis acidic) and halide anions (nucleophilic) promote the cycloaddition reaction. A possible mechanism is proposed.
Bi-functional catalyst, cycloaddition, carbon dioxide, epoxides, Zn-EDTA complexes.
State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, Hunan, China.