Branched phosphazenium salts as effective and versatile cocatalysts for epoxide/CO2 coupling

Abstract

Branched phosphazenium salts of general formula [(Me₂N)₃PN]₄P⁺X⁻ (X⁻ = Cl⁻ or N₃⁻) have been tested as cocatalysts for different catalyst systems, such as salen-type chromium and porphyrin cobalt complexes, in the alternating copolymerization of CO₂ and epoxides (CHO and PO) under various experimental conditions. Higher monomer conversion than that obtained with the benchmark PPN⁺X⁻ counterparts under the same conditions was achieved. The polymers obtained have comparable or greater molar masses. Thus, phosphazenium salts can be viable, if not superior, alternatives to onium salts in CO₂/epoxide ROCOP.