Synthesis and characterization of Mannich base monophenolate lanthanide complexes and their application in ring-opening polymerization of ε-caprolactone

A series of Mannich base monophenol ligands [2,4‐tBu2‐6‐CH2NMe2‐PhOH (HA), 2,4‐tBu2‐6‐CH2NEt2‐PhOH (HB), 2,4‐tBu2‐6‐CH2Py‐PhOH (HC), 2‐tBu‐4‐Me‐6‐CH2Py‐PhOH (HD), 4‐tBu‐2,6‐(CH2Py)2‐PhOH (HE)] were synthesized by Mannich reaction using phenol and formaldehyde reacting with secondary amine. A series of homoleptic lanthanide complexes [LaA3 (1), GdA3 (2), LaB3 (3), GdB3 (4), LaC3 (5), GdC3 (6), LaD3 (7), GdD3 (8), LaE3 (9), GdE3 (10)] were prepared by amine elimination reactions of the ligands with Ln[N(SiMe3)2]3 (Ln = La, Gd). Complexes 1, 3, 5, 7 and 9 were all characterized using NMR spectra, and the structures of complexes 3 and 5 were determined using single‐crystal X‐ray diffraction. Complexes 3 and 5 are isostructural, and the lanthanum center exhibits a distorted octahedral geometry, in which the O(1), O(2) and O(3) atoms occupy three positions and N(1), N(2) and N(3) atoms occupy the other three positions. All complexes were characterized using elemental analysis and infrared spectra. The catalytic properties of complexes 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 for the ring‐opening polymerization of ε‐caprolactone were studied, and the results show that all complexes are efficient initiators for this ring‐opening polymerization reaction. Copyright © 2016 John Wiley & Sons, Ltd. A series of homoleptic lanthanide complexes [LaA3 (1), GdA3 (2), LaB3 (3), GdB3 (4), LaC3 (5), GdC3 (6), LaD3 (7), GdD3 (8), LaE3 (9), GdE3 (10)] were prepared by the amine elimination reactions of ligands reacting with Ln[N(SiMe3)2]3 (Ln = La, Gd). Complexes 1, 3, 5, 7 and 9 were all characterized. Complexes 3 and 5 were determined using single‐crystal X‐ray diffraction. The catalytic properties of complexes 1‐10 in the ring‐opening polymerization of ε‐caprolactone were studied.