Preparation, Characterization, and Catalytic Studies of Magnesium Complexes Supported by NNO-Tridentate Schiff-Base Ligands

A series of magnesium benzyl alkoxides, [LMg(μ-OBn)]2 (1−8), supported by NNO-tridentate Schiff-base ligands are prepared by the reactions of Mg(OBn)2 with one molar equivalent of related Schiff-base ligands (L1H−L8H) in toluene. The molecular structures of compounds 2, 3, 7, and 8 are characterized by X-ray structure determination. All of these compounds are crystallized as penta-coordinated dimers, and the central magnesium atoms are bridged by the oxygen atoms of benzyl alkoxides. The catalytic activities of complexes 1−8 toward the ring-opening polymerization of l-lactide are investigated. Experimental results indicate that the reactivity of [LMg(μ-OBn)]2 (1−8) is dramatically affected by the electronic effect of the substituents on the Schiff-base ligands, and 4 has the highest activity among them.