Bis(3,5-dimethylpyrazole) copper(II) and zinc(II) complexes as efficient initiators for the ring opening polymerization of 蔚-caprolactone and d,l-lactide
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- 作者：Divambal Appavoo ; Bernard Omondi ; Ilia A. Guzei ; Juanita L. van Wyk ; Orpah Zinyemba ; James Darkwa
- 关键词：Pyrazole ; Copper ; Zinc ; Initiators ; Ring opening polymerization ; 蔚-Caprolactone ; d ; l-Lactide
- 刊名：Polyhedron
- 出版年：17 February, 2014
- 年：2014
- 卷：69
- 期：Complete
- 页码：55-60
- 全文大小：704 K
文摘
3,5-Dimethylpyrazole (L), reacts with [Cu(OAc)2] or [Zn(OAc)2]; and either C6H5COOH, 4-OH-C6H5COOH, 3,5-NO2-C6H5COOH or 2-Cl-C6H5COOH to afford the corresponding metal complexes: [Cu(C6H5COO)2(L)2] (1), [Cu(2-Cl-C6H4COO)2(L)2] (2), [Cu(3,5-NO2-C6H3COO)2(L)2] (3), [Cu(4-OH-C6H4COO)2(L)2] (4), [Zn(C6H5COO)2(L)2] (5), [Zn(2-Cl-C6H4COO)2(L)2] (6), [Zn(3,5-NO2-C6H3COO)2(L)2] (7), [Zn(4-OH-C6H4COO)2(L)2] (8). The diamagnetic zinc complexes were characterized by IR, NMR spectroscopy and elemental analysis; while the paramagnetic copper complexes were only characterized by IR spectroscopy, elemental analysis and 1 and 2 were further characterized by single crystal X-ray diffraction studies. All eight complexes are very good initiators for the ring opening polymerization (ROP) of 蔚-caprolactone and d,l-lactide at elevated temperatures, under solvent-free conditions and in toluene respectively; producing polycaprolactone (PCL) and poly(d,l-lactide) (PLA) of moderate molecular weights (ca 4757 Da for PCL and 2484 Da for PLA) and narrow polydispersity indices (1.36 for PCL and 1.42 for PLA). The 13C{1H} NMR spectra indicate the stereochemistry of PLA is heterotactic.