Salicylaldimine-aluminum complexes for the facile and efficient ring-opening polymerization of ε-caprolactone

A facile and efficient catalytic system of salicylaldimine-aluminum complexes for the ring-opening polymerization (ROP) of ε-caprolactone (CL) was investigated. The polymerization of Cl was examined at 25 °C in the presence of 1 mol % of benzyl alcohol (BnOH) using the complex prepared from 1 mol % of AlEt3 and 2 mol % of the ligand in situ. The ligands with a sterically demanding imine moiety enhances the polymerization. The results suggested that one ligand chelated the Al center but the other was monodentate, and the conformation is highly restricted.