Significant enhancement of catalytic properties in mononuclear yttrium complexes by nitrophenolate-type ligands: Synthesis, structure, and catalysis for lactide polymerization

Abstract

The syntheses, structures, and catalytic properties for lactones polymerization of eight novel yttrium complexes containing an amine-bis(benzotriazole phenolate) ( C1NNBiBTP) ligand are reported. A series of nitrophenolate (NP)-type of ligands possessing R substituents with variable electronic properties (R = NO2, Cl, H, CH3) on ortho and/or para position attached to the phenolate rings have been selected and further reacted with C1NNBiBTP-H2 proligand and YCl3·6H2O. Two series of complexes, [Y( C1NNBiBTP)(TNP)(MeOH)2] (3), [Y( C1NNBiBTP)(2,4-DNP)(MeOH)2] (4) and [Y( C1NNBiBTP)(2,5-DNP)(MeOH)2] (5) with two MeOH molecules as initiators as well as [Y( C1NNBiBTP-H)(CNP)2] (6), [Y( C1NNBiBTP-H)(2-NP)2] (7) and [Y( C1NNBiBTP-H)(MNP)2] (8) with two NP derivatives, were synthesized. Their ring-opening polymerizations of L-lactide (L-LA) were investigated for all complexes in order to further understand the correlations between the inductive effect of substitutions and catalytic properties. Particularly, the activity and controllability of yttrium complexes 3 and 5 were improved dramatically comparing with the literature complex with the similar coordination environment, [Y( C1NNBiBTP)(NO3)(MeOH)2], which can be a successful example to enhance the catalytic properties by exchanging coordinate molecules. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2038–204