This comprehensive tutorial review focuses on well-defined cobalt complexes that serve as homogeneous catalysts for the production of polycarbonates and cyclic carbonates from the coupling of carbon dioxide and epoxides. Special considerations are given to the mechanistic pathways involved in these processes.

Excellent activity and selectivity in the copolymerization of CO₂ with epoxides at extremely mild temperature and pressure are observed in the presence of binary nucleophile–electrophile catalyst systems based on chiral [(salcy)Co^IIIX] complexes and quaternary ammonium salts (see scheme). Completely alternating copolymers are obtained with >95 % head-to-tail linkages.