Three aluminum complexes supported by salen ligands derived from cis-1,2-cyclohexanediamine and salicylaldehyde derivatives were synthesized. They were characterized by H-1, C-13 NMR spectra, and elemental analysis. X-ray diffraction analysis revealed that aluminum was in distorted square pyramidal geometry in 2. These complexes were employed as catalysts for the ring-opening polymerization (ROP) of L-lactide and rac-lactide. Complex 2 showed the highest activity among these complexes with isopropanol for the ROP of L-lactide and 3 showed the highest stereoselectivity for the ROP of rac-lactide attaining partially isotactic polylactide with a P-m of 0.75. The kinetic data of the polymerization utilizing 3 as catalyst showed that the polymeric rate was first order to the monomer and catalyst.
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