Ring-opening polymerization of cyclic esters initiated by lithium aggregate containing bis(phenolate) and enolate mixed ligands

A novel lithium aggregate complex [(μ2-/μ3-EDBP)2(OCHCH2)Li5(THF)4] (1) has been synthesized by the reaction of 2,2′-ethylidenebis(4,6-di-tert-butyl-phenol) (EDBP-H2) with 2.5 eq nBuLi in tetrahydrofuran with high yield. The structure of complex 1 is determined by 1H-NMR and X-ray crystallography. Complex 1 can initiate the living ring-opening polymerization of ε-caprolactone and l-lactide yielding polymers with narrow molecular weight distributions, and moreover to prepare the PCL-b-PLA block copolymer.