Origin of "multisite-like" ethylene polymerization behavior of the single-site nonsymmetrical bis(imino)pyridine iron(II) complex in the presence of modified methylaluminoxane

Nina V. Semikolenova, Wen Hua Sun, Igor E. Soshnikov, Mikhail A. Matsko, Olga V. Kolesova, Vladimir A. Zakharov, Konstantin P. Bryliakov

Research output: Contribution to journalArticlepeer-review

46 Citations (Scopus)

Abstract

A detailed study of the effect of reaction temperature, time, and cocatalyst composition on the ethylene polymerization performance of 2-[1-(2,6-dibenzhydryl-4-chlorophenylimino)ethyl]-6-(1-mesityliminoethyl)pyridyliron dichloride (1) is reported. In the presence of modified methylaluminoxane (MMAO), 1 behaves like a highly active, "multisite-like" ethylene polymerization catalyst, with the resulting polyethylenes having time-dependent bimodal-like molecular-weight distributions and featuring saturated (n-propyl- and i-butyl-terminated) chain ends. To readily distinguish between bimodal and bimodal-like molecular-weight distributions, we have proposed the use of the dNf/(d log M) - log M representation further to the mainstream dWf/(d log M) - log M one. The consensus mechanism of chain transfer and chain-end formation in the presence of MMAO has been proposed, which explains the composition and amount of terminal alkyl groups in the polymer, and the apparent "multisite-like" nature of the iron catalyst. A comparison between the catalytic behaviors of the "multisite-like" 1/MMAO catalyst system and the truly multisite catalyst system based on Brookhart's symmetrical bis(imino)pyridine iron catalyst 2 is given. (Graph Presented).

Original languageEnglish
Pages (from-to)2868-2877
Number of pages10
JournalACS Catalysis
Volume7
Issue number4
DOIs
Publication statusPublished - 7 Apr 2017

Keywords

  • Bis(imino)pyridine
  • Chain transfer
  • Ethylene polymerization
  • MMAO
  • Molecular-weight distribution
  • Multisite catalysts
  • bis(imino)pyridine
  • molecular-weight distribution
  • ACTIVATION
  • PRECATALYSTS
  • 2,6-BIS(IMINO)PYRIDYL COMPLEXES
  • ethylene polymerization
  • POLYETHYLENE
  • FE(II)
  • multisite catalysts
  • chain transfer
  • NEW-GENERATION
  • CATALYSTS
  • COBALT

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