Nickel(0)/Phosphine-Catalyzed Copolymerization of CO ₂ and Cyclohexylallene to Degradable Long-Chain Polyesters

Developing efficient strategies to copolymerize carbon dioxide (CO 2 ) with unsaturated hydrocarbon monomers, such as olefins, to produce CO 2 -based polyesters is highly desirable but remains challenging owing to thermodynamic and kinetic barriers. Herein, we demonstrate that allenes, specifically cyclohexylallene (CA), serve as effective comonomers for one-pot copolymerization with CO 2 . Using a nickel(0)–bidentate diarylphosphine complex, we achieve the statistical copolymerization of CA and CO 2 to deliver long-chain polyester P(CA- co -CO 2 ) with widely spaced ester linkages, via a classical sequence of oxidative addition, coordination–insertion, and reductive elimination. Systematic tuning of both phosphine ligand and solvent reveals their crucial roles in facilitating CO 2 insertion into the Ni–C bond and subsequent allene insertion into the Ni–O bond, thereby driving efficient chain propagation. Notably, incorporation of a small amount of CO 2 into the polymer backbone enhances the degradability of P(CA- co -CO 2 ) while preserving its high thermal stability and glass-transition temperature, compared with the allene homopolymer.