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 beta-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,q-bis(4-tert-butylphenyl)phenyl (4e)) is described. X-ray structure analysis reveals a dinuclear, mu-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.