Double metal cyanide complex based on Zn3[Co(CN)6]2 as highly active catalyst for copolymerization of carbon dioxide and cyclohexene oxide

Double metal cyanide complexes based on Zn-3[Co(CN)(6)](2) were prepared in the presence of different complexing agents and used in the copolymerization of carbon dioxide and cyclohexene oxide. The FTIR and H-1 NMR spectra of the products verified the formation of polycarbonate. Compared with zinc carboxylate, zinc phenoxide, and so forth, these catalysts demonstrated great enhancement of catalytic activity. Their highest turnover number and turnover frequency reached 3300 and 1650 h(-1), respectively, at 90 degreesC. The molar fraction of CO2 (F-CO2) for the copolymers was about 0.44-0.47, and it varied slightly with different catalysts under a temperature of 90 degreesC and a pressure of 3.8 MPa. The study showed that the F-CO2 can reach 0.40 even at 0.6 MPa, and it changed slightly above 3.8 MPa. The reaction rate had little influence on the F-CO2 under our experimental conditions. A relatively low temperature was favorable for the incorporation of CO2. The monitoring of copolymerization revealed the molecular weight was proportional to the reaction conversion. The molecular weight distribution was in the range of 4.5-6, and the reaction rate was proportional to the amount of catalyst that was used. (C) 2004 Wiley Periodicals, Inc.