Novel chromium complexes with a [OSSO]-type bis(phenolato) dianionic ligand mediate the alternating ring-opening copolymerization of epoxides and phthalic anhydride

Four new homogeneous chromium complexes with [OSSO]-type bis(phenolato) dianionic ligand catalysts for the ring-opening copolymerization of phthalic anhydride (PA) and epoxides are reported. Through the structure design, the ligand with a cyclohexylene ring backbone of the chromium complexes is quite beneficial to improving the activity. Of all the cocatalysts employed, DMAP is found to be the most efficient. 1H NMR spectra of the copolymers confirmed the alternating microstructures. This is the first example of a well-defined metal complex with a soft Lewis base as donor for the efficient copolymerization of anhydride and epoxides. Additionally, we demonstrate that poly(4-VCHO-alt-PA) can be conveniently functionalized using a robust free-radical mediated thiol–ene reaction of the pendant vinyl groups.