G. S. Nyamato, M. Alam, S. O. Ojwach
Feb 1, 2016
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21
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Journal
Applied Organometallic Chemistry
Abstract
Reactions of 2-bromo-6-(3,5-dimethyl-1H-pyrazol-1-yl)pyridine (L1) and 2,6-bis(3,5-dimethyl-1H-pyrazol-1-yl)pyridine (L2) with NiCl2 and NiBr2 led to the formation of their respective metal complexes [NiCl2(L1)] (1), [NiBr2(L1)] (2) and [NiBr2(L2)] (3) in moderate to high yields. The complexes were characterized using elemental analyses, mass spectrometry and single-crystal X-ray diffraction for 2. The solid-state structure of 2 confirmed the bidentate coordination mode of L1 and formation of a monometallic compound. Activation of the nickel(II) pre-catalysts with methylaluminoxane afforded active catalysts in the ethylene oligomerization reaction to produce mainly butenes (84–86%). In contrast, activation of nickel(II) pre-catalyst 2 with ethylaluminium dichloride resulted in partial Friedel–Crafts alkylation of the toluene solvent by the preformed oligomers. Complex structure, nature of co-catalyst employed, type of solvent and reaction conditions influenced the catalytic behaviour of these pre-catalysts. Copyright © 2015 John Wiley & Sons, Ltd.