Pyrazolyl iron, cobalt, nickel, and palladium complexes: Synthesis, molecular structures, and evaluation as ethylene oligomerization catalysts

Michael K. Ainooson, Stephen O. Ojwach, Ilia A. Guzei, Lara C. Spencer, James Darkwa

Research output: Contribution to journalArticlepeer-review

54 Citations (Scopus)

Abstract

Reactions of [2-(3,5-dimethyl-pyrazol-1-yl)-ethanol] (L1) and [1-(2-chloro-ethyl)-3,5-dimethyl-1H-pyrazole] (L2) with Fe(II), Co(II), Ni(II), and Pd(II) salts gave the complexes [(L1)2FeCl2] (1), [(L1)2CoCl2] (2), [(L1)2NiBr2] (3), [(L1)2Pd(Me)Cl] (5), [(L2)2CoCl2] (6), and [(L2)2NiBr2] (7). Whereas L2 behaves as a monodentate ligand, L1 can behave as either a monodentate or bidentate ligand depending on the nature of the metal centre. For palladium, L1 is monodentate in the solid state structure of 5 but bidentate in the structure of 4, obtained during attempts to crystallize 3. While the activation of iron, cobalt and palladium complexes with EtAlCl2 did not produce active ethylene oligomerization catalysts, the nickel complexes 3 and 7 produced active ethylene oligomerization catalysts. Activities as high as 4329 kg/mol Ni h were obtained. Catalyst 3 produced mainly butenes (57%) and hexenes (43%); of which a combined 20% were converted to Friedel-Crafts alkylated-toluene. Catalyst 7, on other hand, produced mainly butenes (90%) and small amounts of hexenes (10%) which were then completely converted to the corresponding Friedel-Crafts alkylated-toluene products. This difference in product distribution in catalysis performed by complexes 3 and 7 is indicative of the role of the OH functionality in L1 on the EtAlCl2 co-catalysts.

Original languageEnglish
Pages (from-to)1528-1535
Number of pages8
JournalJournal of Organometallic Chemistry
Volume696
Issue number8
DOIs
Publication statusPublished - 15 Apr 2011

Keywords

  • Catalysts
  • Ethylene oligomerization
  • Friedel-Crafts alklylation
  • Metal complexes
  • Pyrazolyl ligands

ASJC Scopus subject areas

  • Biochemistry
  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

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