Alternating Copolymerization of Carbon Dioxide and Epoxide by a Nickel Thiaporphyrin Complex

In this study, we report on the alternating copolymerization of carbon dioxide and cyclohexene oxide by a newly designed nickel thiaporphyrin complex [(STTP)NiCl; 1] catalyst. The copolymerization of cyclohexene oxide in the presence of 1 in THF at 40 degrees C under 50 atm of CO2 selectively produced poly(cyclohexene carbonate) (PCHC). The dependence of this polymerization system on solvent, temperature, and CO2 pressure was examined. Furthermore, a series of Lewis bases or quaternary salts were added as a cocatalyst, revealing that the alternating manner of PCHC was definitively improved by using triphenylphosphine (Ph3P). The dependence of the polymerization system on the [1]/[Ph3P] ratio was further examined.