Synthesis and Characterization of Heterodinuclear Indium(III)/Sodium(I) Complexes Containing Benzotriazole-Derived Phenolate Ligands: Effective Catalysts for Ring-Opening Copolymerization of Carbon Dioxide with Epoxides

This study reported for the first time the facile synthesis of a series of novel structurally well-characterized heterodinuclear indium(III)/sodium(I) dihalide complexes containing benzotriazole-based bis(amino-phenolate) derivatives. All heterobimetallic In(III)/Na(I) complexes were found to be active single-component catalysts for the copolymerization of carbon dioxide (CO2) with cyclohexene oxide (CHO). Noteworthily, In/Na chloro complex 1 has been shown to give high copolymerization selectivity possessing >99% carbonate repeated units for CO2-derived poly(cyclohexene carbonate) production and displayed a turnover number of >1400 under the optimized conditions. Apart from the CO2/CHO copolymerization, the same complex was capable of mediating the CO2-copolymerization of 4-vinyl-1,2-cyclohexene oxide or cyclopentene oxide to deliver the related CO2-based polycarbonates. To the best of our knowledge, complex 1 in this work appears to be the first example of In/Na halide complex-promoted CO2/epoxide copolymerization that enabled the generation of aliphatic polycarbonates with good productivity and high product selectivity.