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An Examination of the Steric and Electronic Effects in the Copolymerization of Carbonyl Sulfide and Styrene Oxide
An Examination of the Steric and Electronic Effects in the Copolymerization of Carbonyl Sulfide and Styrene Oxide
The completely alternating copolymerization of carbonyl sulfide(COS) and styrene oxide was found to occur under mild reaction conditions (0?30 °C and 1.5 MPa) in the presence of (salen)CrCl/onium salt catalyst systems toafford high molecular weight poly(monothiocarbonates) with narrow molecularweight distributions. Ring-opening of styrene oxide was shown to be 88% selectiveat the methylene carbon. That is the reaction is driven by steric hindrance, wherering-opening occurs preferentially at the less congested carbon center. Similarresults were found upon utilizing the tetramethyltetraazaannulene (tmtaa)CrCl/onium salt catalyst. On the other hand, upon employing a zinc?cobalt doublemetal cyanide (Zn?Co DMCC) catalyst, where the ligands around the active zincsite are not sterically encumbering, ring-opening of styrene oxide occurspredominantly at the methine carbon site; i.e., the reaction is electronically driven.
