The Ethylsulfinate Ligand: A Highly Efficient Initiating Group for the Zinc β-Diiminate Catalyzed Copolymerization Reaction of CO₂ and Epoxides

The quantitative synthesis of a series of new zinc(II) sulfinate complexes (4a−e) by insertion of SO2 into zinc−ethyl bonds of β-diiminate complexes ((ArNC(CH3)CH(CH3)CNAr)Zn(O(SO)Et); Ar = 2,6-diisopropylphenyl (4a), 2,6-diethylphenyl (4b), 2-ethyl-6-isopropylphenyl (4c), 2,6-diphenylphenyl (4d), 2,6-bis(4-tert-butylphenyl)phenyl (4e)) is described. X-ray structure analysis reveals a dinuclear, μ-ethylsulfinate-bridged structure for 4a in the solid state, which in solution exists in an equilibrium with the mononuclear species. The easily accessible complexes 4a−c are highly active catalysts for the alternating copolymerization of CO2 and cyclohexene oxide, leading to products with narrow molecular weight distributions.