Nickel(II) complexes chelated by N^N (benzimidazolylmethyl)amine ligands: Synthesis and catalytic behavior in tandem ethylene oligomerization and Friedel-Crafts alkylation reactions

• Published in: Inorganica Chimica Acta Vol. 467; pp. 400 - 404
• Main Authors: Ngcobo, Makhosonke, Ojwach, Stephen O.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-10-2017; Elsevier Science Ltd
• Subjects: Alkylation; Cascade chemical reactions; Catalysis; Catalysts; Chemical reactions; Chemical synthesis; Complexes; Coordination compounds; Ethylene; Friedel-Crafts reaction; Infrared spectroscopy; Ligands; Magnetic moments; Mass spectrometry; Nickel; Oligomerization; Oligomers; Toluene; Ligands; Nickel; Oligomerization; Complexes; Ethylene
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/j.ica.2017.08.040

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•Nickel(II) complexes of (benzimidazolylmethyl)amine ligands synthesized.•The complexes form active catalysts in ethylene oligomerization reactions.•EtAlCl2 co-catalyst in toluene results in the formation of alkyl-toluenes.•While EtAlCl2 in chlorobenzene gives mainly butene and hexene oligomers.•The use of MAO gives predominantly butene and hexene oligomers.
Reactions of N-(1H-benzimidazol-2-ylmethyl)-2-analine (L1), N-(1H-benzimidazol-2-ylmethyl)-2-bromoanaline (L2), N-(1H-benzimidazol-2-ylmethyl)-2-methoxyanaline (L3) and N-(1H-benzimidazol-2-ylmethyl)-2-phenolanaline (L4) with the appropriate nickel(II) salts afforded the respective complexes [Ni(L1)Br2] (1), [Ni(L2)Br2] (2), [Ni(L3)NiBr2] (3), [Ni(L3)Cl2] (4), [Ni(L4)Br] (5) and [Ni(L4)Cl2] (6) in good yields. The structural elucidation of the complexes was achieved using IR spectroscopy, mass spectrometry, magnetic moment measurements and elemental analyses. Upon activation with EtAlCl2 or MAO as co-catalysts, complexes (1–6) formed active catalysts for ethylene oligomerization reactions in addition to Friedel-Crafts alkylation reactions of the preformed oligomers depending on the co-catalyst and solvent system. While activation with EtAlCl2 in toluene produced Friedel-Crafts alkylated products, the use of MAO resulted in the production of mainly C4 and C6 oligomers.