Comparison of structurally analogous Zn2, Co2, and Mg2 catalysts for the polymerization of cyclic esters

Three dimetallic monoethoxide complexes supported by a binucleating phenoxide ligand, LM2Cl2OEt (M = Zn, Co, or Mg), were prepared and shown by X-ray crystallography to be structurally analogous. Comparative studies of their cyclic ester polymerization reactivity revealed different trends for reactions with epsilon-caprolactone and lactide, however, implicating complicated effects of metal ion variation in these polymerizations.