Anionic lanthanide phenoxide complexes as novel single‐component initiators for the polymerization of ε‐caprolactone and trimethylene carbonate

The anionic lanthanide-sodium-2,6-di-tert-butyl-phenoxide complexes [Ln(OAr)4][Na(DME)3]·DME (Ln = Nd 1 (neodymium), Sm 2 (samarium), or Gd 3 (gadolium); DME = dimethoxyethane) were synthesized by the reaction of anhydrous LnCl3 with 4 equiv of sodium-2,6-di-tert-butyl-phenoxide NaOAr in high yields and structurally characterized. These complexes showed high catalytic activity in the ring-opening polymerizations of ϵ-caprolactone (ϵ-CL) and trimethylene carbonate (TMC). The catalytic activity profoundly depended on the lanthanide metals. The active order of Gd < Sm < Nd for the polymerization of ϵ-CL and TMC was observed. The polymers obtained with these initiators all showed a unimodal molecular weight distribution, indicating that the [Ln(OAr)4][Na(DME)3]·DME anionic complexes could be used as single-component initiators. The anionic complex was more efficient than the corresponding neutral complex, Ln(OAr)3(THF)2. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1210–1218, 2007