LAUSR

Abstract Condensation reactions of 2-aminoethanol with the appropriate aldehyde gave ligands 2-[1-[(2-hydroxyethyl)imino]ethyl]phenol (L1) and 2-[(2-hydroxyethyl)imino] methyl]phenol (L2) respectively. Subsequent reductions of L1 and L2 with NaBH4 afforded the corresponding amine ligands 2-[1-[(2-hydroxyethyl)amino]ethyl]phenol (L3) and 2-{[(2-hydroxyethyl)amino]methyl}phenol (L4). Reactions of L1-L4 with either NiCl2 or NiBr2(DME) produced the nickel(II) complexes Ni(L1)Br2] (1), [Ni(L1)Cl2] (2), [Ni(L2)Cl2] (3) and [Ni(L3)Br2] (4) respectively. Structural elucidation of the compounds were performed using NMR, IR, mass spectrometry, elemental analyses and single crystal X-ray crystallography for complex 3. All the nickel(II) complexes formed active catalysts in ethylene oligomerization reactions upon activation with EtAlCl2 co-catalyst to afford butenes (20%–100%) and hexenes (31%–80%) as the major products. Higher catalytic activities of up to 11 830 kg mol−1 h−1 and formation of exclusively butenes were realized depending on the complex structure and reactions conditions.