Investigating the Effects of
Para -methoxy Substitution in Sterically Enhanced Unsymmetrical Bis(arylimino)pyridine-cobalt Ethylene Polymerization CatalystsInvestigating the Effects of
Para -methoxy Substitution in Sterically Enhanced Unsymmetrical Bis(arylimino)pyridine-cobalt Ethylene Polymerization Catalysts- Chinese Journal of Polymer Science 2022年40卷第3期 页码：266-279
- Affiliations：
a.Institute of Applied Chemistry, Shanxi University, Taiyuan 030006, China
b.Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Sciences, Institute of Chemistry Chinese Academy of Sciences, Beijing 100190, China
c.Department of Chemistry, University of Leicester, University Road, Leicester LE1 7RH, UK
d.State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China
- Author bio：
yuansf@sxu.edu.cn (S.F.Y.)
gas8@leicester.ac.uk (G.A.S.)
whsun@iccas.ac.cn (W.H.S.)
- Funds：This work was financially supported by the National Natural Science Foundation of China (No. 21871275). G.A.S. thanks the Chinese Academy of Sciences for a President's International Fellowship for Visiting Scientists.
DOI：10.1007/s10118-022-2670-z
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Yi Yan, Shi-Fang Yuan, Ming Liu, 等. Investigating the Effects of
Para -methoxy Substitution in Sterically Enhanced Unsymmetrical Bis(arylimino)pyridine-cobalt Ethylene Polymerization Catalysts[J]. Chinese Journal of Polymer Science, 2022,40(3):266-279.Yi Yan, Shi-Fang Yuan, Ming Liu, et al. Investigating the Effects of
Para -methoxy Substitution in Sterically Enhanced Unsymmetrical Bis(arylimino)pyridine-cobalt Ethylene Polymerization Catalysts[J]. Chinese Journal of Polymer Science, 2022,40(3):266-279.Yi Yan, Shi-Fang Yuan, Ming Liu, 等. Investigating the Effects of
Para -methoxy Substitution in Sterically Enhanced Unsymmetrical Bis(arylimino)pyridine-cobalt Ethylene Polymerization Catalysts[J]. Chinese Journal of Polymer Science, 2022,40(3):266-279. DOI： 10.1007/s10118-022-2670-z.Yi Yan, Shi-Fang Yuan, Ming Liu, et al. Investigating the Effects of
Para -methoxy Substitution in Sterically Enhanced Unsymmetrical Bis(arylimino)pyridine-cobalt Ethylene Polymerization Catalysts[J]. Chinese Journal of Polymer Science, 2022,40(3):266-279. DOI： 10.1007/s10118-022-2670-z.
摘要
Abstract
A group of five bis(arylimino)pyridine-cobalt(II) chloride complexes, [2-{(2,6-(Ph,2,CH),2,-4-MeOC,6,H,2,)N＝CMe}-6-(ArN＝CMe)C,5,H,3,N]CoCl,2, (Ar = 2,6-Me,2,C,6,H,3,Co1, 2,6-Et,2,C,6,H,3,Co2, 2,6-iPr,2,C,6,H,3,Co3, 2,4,6-Me,3,C,6,H,2,Co4, 2,6-Et,2,-4-MeC,6,H,2,Co5,), each containing one ,N,-4-methoxy-2,6-dibenzhydrylphenyl group and one smaller sterically/electronically variable ,N,-aryl group, have been synthesized in good yield (,>,71%) from the corresponding neutral terdentate nitrogen-donor precursor,L1,–,L5,. All complexes have been characterized by ,1,H-NMR and FTIR spectroscopy with the former highlighting the paramagnetic nature of these cobaltous species and the unsymmetrical nature of the chelating ligand. The molecular structures of ,Co3, and ,Co4, emphasize the steric differences of the two inequivalent ,N,-aryl groups and the distorted square pyramidal geometry about the metal centers. In the presence of MAO or MMAO,Co1,–,Co5, collectively displayed high activities for ethylene polymerization producing high molecular weight polyethylenes that, in general, exhibited narrow dispersities (,M,w,/,M,n, values: 2.12–4.07). Notably, the least sterically hindered ,Co1, when activated with MAO was the most productive (6.92×10,6, g,PE,·mol,−1,(Co),·h,−1,) at an operating temperature of 60 ºC. Conversely, the most sterically hindered ,Co3,/MMAO produced the highest molecular weight polyethylene (,M,w,=6.29×10,5, g·mol,−1,). All the polymers displayed high linearity as demonstrated by their melting temperatures (,>,130 °C) and their,1,H- and ,13,C-NMR spectra. By comparison of ,Co1, with its ,para,-methyl, -chloro and -nitro counterparts, the presence of the ,para,-methoxy substituent showed the most noticeable effect of enhancing the thermal stability of the catalyst.
关键词
Keywords
Cobalt(II) precatalystEthylene polymerizationHigh molecular weight polyethyleneElectronic effectsThermal stability
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