Metal amino-bis(phenolate) complexes as catalysts for copolymerization of carbon dioxide, epoxides and anhydrides

Cyclic and polycarbonate synthesis from CO₂ and epoxides is a promising method of using CO₂ as a C-1 feedstock. Catalysts to-date have shown the breadth of active metal complexes include Zr, Cr, Fe, Co, Ni, Zn containing systems with diverse multidentate ligands. We have focused our attention on the amino-bis(phenolate) ligand framework, which is highly modifiable both sterically and electronically. These ligands can be paired with metals from across the periodic table including both main group and transition metals. This work will present a survey of comparable activities for early, mid and late transition metal complexes of amine-bis(phenolate) ligands for polymerization reactions of CO₂ with epoxides, as well as cyclic ester ring-opening polymerization and ring-opening copolymerization of epoxides with cyclic anhydrides. Mechanistic studies and kinetic data obtained by in situ IR spectroscopy will be discussed along with structure/activity relationships resulting from steric and electronic modification of the ligand systems.