(Pyrazolylethyl-amine)zinc(II) carboxylate complexes as catalysts for the copolymerization of CO2 and cyclohexene oxide
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Date
2022
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Polyhedron
Abstract
Pyrazolyl compounds 2-(3,5-di-tert-butyl-1H-pyrazol-1-yl)ethyl-amine) (L1), 2-(3,5-diphenyl-1H-pyrazol-
1-yl)ethyl-amine (L2), and 2-(3-phenyl-5-(trifluoromethyl)-1H-pyrazol-1-yl)ethyl-amine (L3) were
reacted with a mixture of zinc(II) acetate and 3,5-dinitrobenzoic acid to form the bidentate complexes
[(2-(3,5-di-tert-butyl-1H-pyrazol-1-yl)-ethyl-amine)-Zn(C6H5COO(NO2)2] (1), [(2-(3,5-diphenyl-1Hpyrazol-
1-yl)ethyl-amine)Zn(C6H5COO(NO2)2] (2), and [(2-(5-phenyl-3-(trifluoro-methyl)-1H-pyrazol-
1-yl)ethyl-amine)Zn(C6H5COO(NO2)2] (3) respectively. All three zinc complexes were tested as catalysts
for the copolymerization of CO2 and cyclohexene oxide (CHO) and found active to form poly(cyclohexene
carbonate) (PCHC) and cyclohexene carbonate (CCHC) at CO2 pressures as low as 1.5 MPa and under solvent-
free conditions in the absence of a co-catalyst. Increase in CO2 pressure resulted in activity and
showed selectivity up to 99% selectivity for the formation of the copolymer PCHC. Optimum temperature
for the polymerization was 100 C and even at this temperature selectivity towards formation
of PCHC was found to be 99%. The copolymers obtained have moderate molecular weights
(3860–11,500 g/mol) and polydispersity indices varying from 2.73 to 4.93.
Description
Research Article
Keywords
Zinc(II) complex, Pyrazole, Poly(cyclohexene carbonate), Cyclohexene carbonate, Carbon dioxide