Chromium complexes containing a tetradentate [OSSO]-type bisphenolate ligand as a novel family of catalysts for the copolymerization of carbon dioxide and 4-vinylcyclohexene oxide

This work reports the synthesis of polycarbonates from 4-vinylcyclohexene oxide (VCHO)/carbon dioxide copolymerization catalyzed by new homogeneous chromium complexes with an [OSSO]-type bis(phenolato) dianionic ligand. Through the structural design, the ethylene-bridged ligands of the chromium complex exhibit the highest activity with the same axial anion Cl. The catalytic activity and product selectivity of these [OSSO]CrIII complexes have been systematically investigated under varied conditions. The 1H NMR spectrum of the obtained copolymers confirmed the resulting polycarbonate with high CO2 incorporation with a carbonate unit above 95%. This is one of the rare examples of a well-defined metal complex with a soft Lewis base as a donor for the efficient copolymerization of carbon dioxide and epoxides.