This paper describes the synthesis of (pyridyl)benzoazole Zn(II) and Cu(II) complexes and their applications as catalysts in ring-opening polymerization (ROP) of e-caprolactone (e-CL). Reactions of 2-(3-pyridyl)-1H-benzimidazole (L1), 2-(2-pyridyl)-1H-benzothiazole (L2) and 2-(2-pyridyl)-1H-benzimidazole (L3) with Zn(II) and Cu(II) acetates produced the corresponding complexes; [Zn 2 (L1) 2 (OAc) 4 )] (1), [Cu 2 (L1) 2 (OAc) 4 ] (2), [Zn(L2)(OAc) 2 )] (3), [Zn(L3)(OAc) 2 )] (4) and [Cu(L3),-(OAc) 2 )] (5). Molecular structures of complexes 2 and 5arevealed that while L1 adopts a monodentate binding mode, through the pyridyl nitrogen atom, L3 exhibits a bidentate coordination mode. All the complexes formed active catalysts in the ROP of e-CL to afford moderate molecular weight polymers. The kinetics of the ROP reactions of e-CL were pseudo-first-order with respect to monomer and catalysts.
The kinetics, mechanism and polymer microstructure studies of ring-opening polymerization (ROP) of lactides (LA) by Zn(II) and Cu(II) complexes of (pyrazolylmethyl)pyridine ligands, 2-(3,5-dimethylpyrazol-1-ylmethyl)pyridine (L1) and 2-(3,5-diphenylpyrazol-1-ylmethyl)pyridine (L2) is described. The complexes [Zn (
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