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Exceptionally high molecular weight linear polyethylene by using N,N,N′-Co catalysts appended with a N′-2,6-bis{di(4-fluorophenyl)methyl}-4-nitrophenyl group

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journal contribution
posted on 27.08.2019, 13:47 by R Zhang, Y Ma, M Han, GA Solan, Y Pi, Y Sun, WH Sun
The bis(arylimino)pyridines, 2-[CMeN{2,6-{(4-FC6H4)2CH}2–4-NO2}]-6-(CMeNAr)C5H3N (Ar = 2,6-Me2C6H3 L1, 2,6-Et2C6H3 L2, 2,6-i-Pr2C6H3 L3, 2,4,6-Me3C6H2 L4, 2,6-Et2–4-MeC6H2 L5), each containing one N′-2,6-bis{di(4-fluorophenyl)methyl}-4-nitrophenyl group, have been synthesized by two successive condensation reactions from 2,6-diacetylpyridine. Their subsequent treatment with anhydrous cobalt (II) chloride gave the corresponding N,N,N′-CoCl2 chelates, Co1 – Co5, in excellent yield. All five complexes have been characterized by 1H/19F NMR and IR spectroscopy as well as by elemental analysis. In addition, the molecular structures of Co1 and Co3 have been determined and help to emphasize the differences in steric properties imposed by the inequivalent N-aryl groups; distorted square pyramidal geometries are adopted by each complex. Upon activation with either methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), precatalyts Co1 – Co5 collectively exhibited very high activities for ethylene polymerization with 2,6-dimethyl-substituted Co1 the most active (up to 1.1 × 107 g (PE) mol−1 (Co) h−1); the MAO systems were generally more productive. Linear polyethylenes of exceptionally high molecular weight (Mw up to 1.3 × 106 g mol−1) were obtained in all cases with the range in dispersities exhibited using MAO as co-catalyst noticeably narrower than with MMAO [Mw/Mn: 3.55–4.77 (Co1 – Co5/MAO) vs. 2.85–12.85 (Co1 – Co5/MMAO)]. Significantly, the molecular weights of the polymers generated using this class of cobalt catalyst are higher than any literature values reported to date using related N,N,N-bis (arylimino)pyridine-cobalt catalysts.

Funding

This work was supported by the National Natural Science Foundation of China (No. 21871275) and UCAS Joint PhD Training Program (UCAS[2018]19). G.A.S. thanks the Chinese Academy of Sciences for a President's International Fellowship for Visiting Scientists.

History

Citation

Applied Organometallic Chemistry, 2019, e5157

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Chemistry

Version

AM (Accepted Manuscript)

Published in

Applied Organometallic Chemistry

Publisher

Wiley

issn

0268-2605

eissn

1099-0739

Acceptance date

14/07/2019

Copyright date

2019

Publisher version

https://onlinelibrary.wiley.com/doi/full/10.1002/aoc.5157

Notes

The file associated with this record is under embargo until 12 months after publication, in accordance with the publisher's self-archiving policy. The full text may be available through the publisher links provided above.;Additional supporting information may be found online in the Supporting Information section at the end of the article.

Language

en