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Nickel(II) complexes bearing pyrazolylpyridines: synthesis, structures and ethylene oligomerization reactions
Author(s) -
Nyamato George S.,
Alam Mohd. Gulfam,
Ojwach Stephen O.,
Akerman Matthew P.
Publication year - 2016
Publication title -
applied organometallic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.53
H-Index - 71
eISSN - 1099-0739
pISSN - 0268-2605
DOI - 10.1002/aoc.3402
Subject(s) - chemistry , methylaluminoxane , catalysis , nickel , pyridine , ethylene , denticity , toluene , solvent , polymer chemistry , alkylation , crystal structure , medicinal chemistry , organic chemistry , metallocene , polymerization , polymer
Reactions of 2‐bromo‐6‐(3,5‐dimethyl‐1 H ‐pyrazol‐1‐yl)pyridine ( L1 ) and 2,6‐bis(3,5‐dimethyl‐1 H ‐pyrazol‐1‐yl)pyridine ( L2 ) with NiCl 2 and NiBr 2 led to the formation of their respective metal complexes [NiCl 2 (L1)] ( 1 ), [NiBr 2 (L1)] ( 2 ) and [NiBr 2 (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.