Neutral Ni(II) Catalysts based on Maple-Lactone Derived [N,O] Ligands for the Polymerization of Ethylene

Matthew Andrews, Paul Ewing, Martyn C. Henry, Mark Reeves, Paul C. J. Kamer, Bernd H. Müller, Ruaraidh D. McIntosh, Stephen M. Mansell

Research output: Contribution to journalArticle

Abstract

This paper describes the synthesis of neutral nickel(II) catalysts for the polymerization of ethylene. A series of 2-(arylamino)-5-methylcyclopent-2-en-1-one (aryl = 2,6-diisopropylphenyl, 2,4,6-trimethylphenyl, 3,5-dimethylphenyl, and 4-methylphenyl) proligands, derived from the condensation of aryl amines with maple lactone, were synthesized as their keto-enamine tautomers. Deprotonation with NaH gave their respective sodium imino-enolate salts, which underwent salt metathesis with Ni(II) precursors to give square planar [Ni(Ar)(κ 2-imino-enolate)(PPh 3)] (Ar = Ph, ortho-tolyl) complexes containing 5-membered [N,O] chelates. Precatalysts with N-Dipp (Dipp = 2,6-diisopropylphenyl) substituents were found to exhibit moderate activity in the polymerization of ethylene when using B(C 6F 5) 3 or [Ni(cod) 2] (cod = 1,4-cyclooctadiene) as coactivators, producing polymers with a high molecular weight, as determined by GPC. The reaction was found to be highly dependent on temperature, with the catalysts most active at 80 °C. Differences in polymer structure were also found when using B(C 6F 5) 3 or [Ni(cod) 2] as the cocatalyst, with [Ni(cod) 2] producing a more highly branched polymer. Reducing the steric bulk at the N substituent of the ligand led to inactive species.

Original languageEnglish
Pages (from-to)1751-1761
Number of pages11
JournalOrganometallics
Volume39
Issue number10
Early online date17 Apr 2020
DOIs
Publication statusPublished - 26 May 2020

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

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