Reactions of 2-(chloromethyl)-6((3,5-dimethyl-1H-pyrazol-1-yl)methyl)pyridine (L1) and 2-(chloromethyl)-6-((3,5-diphenyl-1H-pyrazol-1-yl)methyl)pyridine (L2) with NiCl2, NiBr2, CoCl2 and FeCl2 led to the formation of their respective metal complexes [NiCl2(L1)] (1), [NiBr2(L1)] (2), [CoCl2(L1)] (3), [FeCl2(L1)] (4), [NiBr2(L2)] (5), and [CoCl2(L2)1 (6) in moderate to high yields. The complexes were characterized by elemental analyses, mass spectrometry and single-crystal x-ray diffraction for 5 and 6. Solid state structures of 5 and 6 confirmed the bidentate coordination modes of L1 and L2 and formation of monometallic compounds. Complexes 1-6 formed active catalysts for the oligomerization of ethylene reactions when activated with either EtAlCl2 or methylaluminoxane (MAO). The catalytic activities of 1-6 and products formed largely depended on the co-catalyst and solvent system. While activation with EtAlCl2, in toluene produced Friedel-Crafts toluene-alkylated products, the use of hexane and chlorobenzene gave predominantly C-4 and C-6 oligomers. On the other hand, activation with MAO in toluene led to the formation of mainly C-4, C-6 and C-8 oligomers. The complex structure and reaction conditions such as co-catalyst/complex ratio, time and pressure also influenced the catalytic behaviour of these pre-catalysts. (C) 2014 Elsevier B.V. All rights reserved.