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Abstract
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Researchers
prepared the pyrazolylamine ligands, 2-(3,5-dimethyl-1H-pyrazol-1-yl)-N-(pyridin-2-ylmethyl)ethan-amine
(L1a),
2-(3,5-di-tert-butyl-1H-pyrazol-1-yl)-N-(pyridin-2-ylmethyl)ethan-amine
(L2a), 2-(3,5-dimethyl-pyrazol-1-yl)-ethyl-(1H-pyrrol-2-ylmethyl)-amine
(L3a), 2-(3,5-di-tert-butyl-pyrazol-1-yl)-ethyl-(1H-pyrrol-2-ylmethyl)-amine
(L4a), by reducing the corresponding imine compounds L1–L4. They then reacted
L1a–L4a with [NiBr2(DME)] to form the nickel complexes, [NiBr2(L1a)] (1),
[NiBr2(L2a)] (2), [NiBr2(L3a)] (3) and [NiBr2(L4a)] (4) in high yields. When
activated with aluminum co-catalysts, all four nickel complexes were able to
catalyze the oligomerization or polymerization of ethylene; but the products
of these reactions were co-catalyst and solvent dependent.
With
EtAlCl2 as co-catalyst and in toluene, researchers formed butene and hexene,
which subsequently alkylated the solvent selectively to butyl-, dibutyl- and
tri-butyltoluene. The same catalysts in chlorobenzene produced butene, hexene
and highly branched polyethylene.
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