Efficient Regioselective Copolymerization of Carbonyl Sulfide and Propylene Oxide with a Tolerant Iron Complex-Based Binary Catalyst

Fixation of carbonyl sulfide (COS) into the sulfur-containing polymer has received much attention due to its unique features. In this study, air-stable and easily synthesized iron(III) aminotriphenolate complexes (APFe) in conjunction with onium salt have been successfully employed for copolymerizing COS with propylene oxide, generating perfectly alternating poly(propylene monothiocarbonate)s (PPMTCs) with a high regioregularity of >99% tail-to-head content. When using bis(triphenylphosphine) iminium chloride (PPNCl) as a cocatalyst, copolymerization gave PPMTCs in outstanding catalytic efficiency of turnover frequency (TOF) up to 128,500 h–1 within 6 min at 80 °C. No oxygen/sulfur atom exchange reaction has occurred at an elevated temperature even up to 100 °C. Notably, the APFe/PPNC binary catalyst exhibits excellent tolerance to a range of impurities including CO, CO2, dried air, N2, and water.