University of Leicester
Browse
191024-manuscript-2_GAS.docx (4.73 MB)

Steric and electronic modulation of iron catalysts as a route to remarkably high molecular weight linear polyethylenes.

Download (4.73 MB)
journal contribution
posted on 2020-02-28, 15:55 authored by Randi Zhang, Mingyang Han, Yanping Ma, Gregory A Solan, Tongling Liang, Wen-Hua Sun
Five structurally related bis(arylimino)pyridine-iron(ii) chloride complexes, [2-[CMeN{2,6-{(4-FC6H4)2CH}2-4-NO2}]-6-(CMeNAr)C5H3N]FeCl2 (Ar = 2,6-Me2C6H3Fe1, 2,6-Et2C6H3Fe2, 2,6-i-Pr2C6H3Fe3, 2,4,6-Me3C6H2Fe4, and 2,6-Et2-4-MeC6H2Fe5), incorporating one N-2,6-bis{di(4-fluorophenyl)methyl}-4-nitrophenyl group and one distinct N-aryl group, have been prepared in good yield through the interaction of the corresponding free ligands (L1-L5) with FeCl2·4H2O. All ferrous complexes were paramagnetic which was manifested by broad and highly shifted peaks in their 1H NMR spectra. The marked steric imbalance imposed by the two inequivalent N-aryl groups was a key feature highlighted in the molecular structures of representative complexes Fe1 and Fe2. Upon activation with either MAO or MMAO, Fe1-Fe5 all exhibited high activities for ethylene polymerization with good thermal stability [activities as high as 1.58 × 107 g (PE) mol-1 (Fe) h-1 at 60 °C], affording especially high molecular weight linear polyethylenes (3.92 × 105 g mol-1 at 70 °C; Tm > 130 °C). To the best of our knowledge, the molecular weights of the polyethylenes produced by the current class of iron catalysts exceed the highest values reported for related bis(imino)pyridine-iron catalysts to date; changes in the ortho-R1 substitution pattern offered some additional fine control of the molecular weight. Moreover, the nature of the aluminoxane co-catalyst employed had a noticeable effect on the polymer end group composition. When using MAO, unsaturated polymers containing both vinyl and n-propyl end groups were evident, whereas with MMAO, fully saturated polymers were generated containing both isobutyl and n-propyl end groups.

Funding

This work was 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.

History

Citation

Dalton transactions, 2019,48, 17488-17498

Author affiliation

Department of Chemistry

Version

  • AM (Accepted Manuscript)

Published in

Dalton transactions

Volume

48

Issue

47

Pagination

17488 - 17498

Publisher

Royal Society of Chemistry (RSC)

issn

1477-9226

eissn

1477-9234

Acceptance date

2019-11-05

Copyright date

2019

Publisher version

https://pubs.rsc.org/en/content/articlelanding/2019/dt/c9dt03880a#!divAbstract

Spatial coverage

England

Language

eng

Usage metrics

    University of Leicester Publications

    Categories

    Exports

    RefWorks
    BibTeX
    Ref. manager
    Endnote
    DataCite
    NLM
    DC