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

• Y and Dy complexes with C1NNBiBTP have been synthesized and characterized.
• Catalytic studies for lactide polymerization of air-stable complexes.
• Complex 6 can efficiently polymerize lactide under solvent-free polymerization.

The syntheses, structures and catalytic properties for lactones polymerization of six new dysprosium and yttrium complexes containing an amine-bis(benzotriazole phenolate) (C1NNBiBTP) ligand with different protonated/deprotonated forms of ligands are reported. Complexes [M(C1NNBiBTP-H3)(NO3)4] (M: Dy(1) and Y(2)) were obtained from the reaction of the C1NNBiBTP-H2 proligand with M(NO3)3·6H2O without an additional base in a dichloromethane (DCM)/acetonitrile (MeCN) mixer. Applying trimethylamine (Et3N) to deprotonate the proligand, bis-nitrate complexes [M(C1NNBiBTP-H)(NO3)2(H2O)]·THF (M: Dy(3·THF) and Y(4·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(C1NNBiBTP)(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.

Structurally diverse dysprosium and yttrium nitrate complexes based on an amine-bis(benzotriazole phenoxide) ligand were developed to behave as air-stable catalysts for lactide (LA) polymerization. Mono-NO3 yttrium complex 6 containing two coordinating methanol molecules was demonstrated to effectively catalyze bulk polymerization of LA in a controlled character.Figure optionsDownload as PowerPoint slide