Structurally diverse dysprosium and yttrium complexes containing an amine-bis(benzotriazole phenolate) ligand: Synthesis, characterization and catalysis for lactide polymerization

The syntheses, structures and catalytic properties for lactones polymerization of six new dysprosium and yttrium complexes containing an amine-bis(benzotriazole phenolate) ((BiBTP)-Bi-C1NN) ligand with different protonated/deprotonated forms of ligands are reported. Complexes [M((BiBTP)-Bi-C1NN-H-3)(NO3)(4)] (M: Dy(1) and Y(2)) were obtained from the reaction of the (BiBTP)-Bi-C1NN-H-2 proligand with M(NO3)(3)center dot 6H(2)O without an additional base in a dichloromethane (DCM)/acetonitrile (MeCN) mixer. Applying trimethylamine (Et3N) to deprotonate the proligand, bis-nitrate complexes [M((BiBTP)-Bi-C1NN-H)(NO3)(2)(H2O)]center dot THF (M: Dy (3 center dot THF) and Y(4 center dot THF)) were obtained from a mixture solution of with tetrahydrofuran (THF) and DCM. Further tuning base-to-proligand ratio followed by MeOH solution yielded mono-nitrate complexes [M((BiBTP)-Bi-C1NN)(NO3)(MeOH)(2)] (M: Dy(5) and Y(6)). Air-stable BiBTP-ligated complexes 1-6 were demonstrated to be active catalysts for lactide (LA) polymerization, and the catalytic performance for these complexes was compared. Particularly, yttrium complex 6 with two coordinating methanol molecules was found to effectively catalyze bulk polymerization of LA in a controlled character due to the presence of alcohol initiators. (C) 2016 Elsevier B.V. All rights reserved.