Di‐ and trivalent rare earth complexes stabilized by sterically demanding aminopyridinato ligands as initiators in ring‐opening polymerization reactions of ϵ‐caprolactone

Abstract Salt elimination protocols using Ap*K Ap*H = (2, 6‐diisopropyl‐phenyl) ‐6‐ (2, 4, 6‐triisopropyl‐phenyl) ‐pyridin‐2‐yl‐amine lead to the rare earth aminopyridinato complex Ap*LuCl 2 (thf) 2, 4. Results of X‐ray crystal structure analyses of 4 and the corresponding single THF coordinated dimer are discussed. Ring‐opening polymerization of ε‐caprolactone initiated by complexes Ap*LaBr 2 (thf) 3, 2, Ap*YbI (thf) 2 2, 3 or 4 in the presence of NaBH 4 allows the preparation, in a short reaction time, of α, ω‐dihydroxytelechelic polymers with high molar mass (M ₍ up to 50, 000) and moderate molar mass distributions (1. 3 < M ₖ / M ₍ < 1. 6). © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3611–3619, 2007