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Keywords:

  • anilido-aldimine;
  • β-butyrolactone;
  • catalyst;
  • magnesium;
  • ring-opening polymerization;
  • zinc

Abstract

Magnesium (Mg) and zinc (Zn) complexes incorporating tridentate anilido-aldimine ligand, (E)-2, 6-diisopropyl-N-(2-((2-(piperidin-1-yl)ethylimino)methyl)phenyl)aniline (AAPip-H, 1), were synthesized and structurally characterized. The reaction of AAPip-H (1) with MgnBu2 or ZnEt2 in equivalent proportions afforded the monomeric complex [(AAPip)MgnBu] (2) or [(AAPip)ZnEt] (3), respectively. The coordination modes of these complexes differ in the solid state: Mg complex 2 shows a four-coordinated and distorted tetrahedral geometry, whereas Zn complex 3 adopts a trigonal planar geometry with a three-coordinated Zn center. Complexes 2 and 3 are efficient catalysts for the ring-opening polymerization of β-butyrolactone (β-BL) in the presence of 9-anthracenemethanol (9-AnOH). The polymerization of β-BL with the Zn catalyst system is demonstrated in a living fashion with a narrow polydispersity index, PDI = 1.01–1.10. The number-averaged molecular weight (Mn) of the produced poly(3-hydroxybutyrate) (PHB) is quite close to the expected Mn over diverse molar ratios of monomer to 9-AnOH. A greater ratio of monomer to alcohol catalyzed by Zn complex 3 served to form PHB with a large molecular weight (Mn > 60000). An effective method to prepare PHB-b-PCL and PEG-b-PHB by the ring-opening copolymerization of β-BL catalyzed by zinc complex 3 is reported. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010