Synthesis and structural characterization of a new tetranuclear Zr complex supported by unsymmetric N2O2 ligand and its catalytic behaviors for ring-opening polymerization of rac-lactide

Abstract

A Zr complex [Zr4L2(μ3-O)2(μ-OMe)2 (OiPr)6] (1) containing two heterochiral N atoms was synthesized from an unsymmetric N2O2 ligand 2-(((2-pyridylmethyl)(2-hydroxyphenyl)amino)methyl)-4,6-di(tert-butyl)phenol (H2L) and characterized by single crystal X-ray diffraction. The complex 1 is an unusual tetranuclear zirconium complex with two oxo-, two methoxy- and two phenoxy-bridges. The four zirconium atoms are unequivalently coordinated. Two Zr atoms are 7-coordinate in a distorted pentagonal bipyramidal geometry, and another two Zr atoms are 6-coordinate in a distorted octahedron geometry. The ring-opening polymerization of rac-lactide catalyzed by complex 1, gave slightly isotactic enriched polylactide with moderate polydispersities.