Binuclear aluminum complexes with amine–imine type ligands derived from 1,3-benzenedialdehyde: synthesis, structures and their catalytic properties in ring-opening polymerization

Abstract

Reaction of 1,3-bis(imino)benzenes with a stoichiometric amount of LiAlH4 in THF yields iminoaminobenzenes L1 and L2. Further reaction of iminoaminobenzenes L1 and L2 with an equivalent of AlR3 in toluene affords macrocyclic binuclear aluminum complexes 1a, 1b, and 2a. These macrocyclic aluminum complexes were characterized by 1H NMR, 13C NMR, and IR spectroscopy. The molecular structures of 1a, 1b, and 2a were further confirmed by X-ray crystallography. X-ray diffraction analysis revealed that 1a, 1b, and 2a adopted a distorted tetrahedral geometry around aluminum. These complexes have efficient activities toward ring-opening polymerization of ε-caprolactone in the presence of benzyl alcohol.