Highly Active and Readily Accessible Proline-Based Dizinc Catalyst for CO2/Epoxide Copolymerization

In the pursuit of CO2-based materials, the development of efficient catalysts for the alternating copolymerization of CO2 and epoxides to give polycarbonates is receiving particular attention. Desirable attributes for such catalysts are high copolymerization activity at low CO2 pressure, as well as chemo- and stereocontrol over the formed polymer. Here, we report a novel chiral zinc catalyst that can be isolated in 97% yield from commercial sources, and that produces polycarbonates selectively from neat cyclohexene oxide under 1bar of CO2 pressure at temperatures above 50 degrees C. At 80 degrees C reaction temperature, TONs of 1684 and initial TOFs up to 149h(-1) were measured, producing an isotactic-enriched polycarbonate with a probability P-m of 65% for the formation of a meso diad. Insight into the dinuclear nature of the active species and the copolymerization progress has been gained from structural and spectroscopic studies.