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. H-1 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.