Phthalic anhydride promoted ring-opening polymerization of cyclohexene oxide catalyzed by dinuclear chromium complex supported by piperazine-bridged [ONSO] ligand

New bimetallic chromium complexes bearing a piperazine-bridged tetradentate-dianionic iminethiobis(phenolate) (ONSO) ligand and an ancillary chloride group (complex 1) have been developed. Of interest, it was found that the complex 1 catalyzed copolymerization of cyclohexene oxide with phthalic anhydride (PA) gives a product with more than 97% ether linkage content, i.e. selective synthesis of poly(cyclohexene oxide), which is in sharp contrast to the mononuclear [ONSO]CrCl analogue where a resulting polymer with more than 86% ester units is achieved under identical conditions. The influences of PA loading, reaction time and temperature on the polymerization were investigated. According to the kinetics data, the apparent activation energy of the ring-opening polymerization of cyclohexene oxide is 12.5 kJ mol(-1). A cationic polymerization mechanism is proposed according to the polymer structure and the interaction between metal complex 1 and PA. (c) 2019 Society of Chemical Industry