A series of new Ni(II) complexes of general formula {NiCl2(L)}(2) [Ni1, L= 5-methyl-2-(C4H3O-2-CH=N)C2H4OPh; Ni2, L= 5-Methyl-2-(C4H3O-2-CH=N)Ph-2-OPh; Ni3, L= 2-(C4H3O-2-CH=N)Ph-2-OPh; Ni4, L= 5-Methyl-2-(C4H3O-2-CH=N)CH2Ph-2-OMe were prepared and characterized by IR spectroscopy, elemental analysis, high-resolution mass spectrometry (HRMS), and X-ray photoelectron spectroscopy (XPS). XPS data suggest no interaction of the pendant ether/furfural donor groups with the nickel metal center. Density functional theory studies indicate the formation of nickel dimeric species with ether-imine-furfural acting as a monodentate ligand. All nickel precatalysts, activated with polymethylaluminoxane-improved performance (PMAO-IP), exhibited moderate to good activities for ethylene oligomerization [TOF = 14.7-57.3 x 10(3) mol(ethylene) mol(Ni)(-1) h(-1)] with high selectivities for production of 1-butene (63.2-83.2 wt.%). Activation of Ni2 using different types of cocatalysts (PMAO-IP, DMAO, MAO or EASC) led to formation of active oligomerization systems with a significant impact on the activity and selectivity. The use of MAO instead of PMAO-IP gave a slight improvement in the TOF [69.3 x 10(3) mol(ethylene)mol(Ni)(-1) h(-1)] with lower selectivity for 1-butene. Higher activity was obtained using EASC as cocatalyst [206.1 x 10(3) mol(ethylene) mol(Ni)(-1) h(-1)] along with a drastic reduction in the selectivity for 1-butene (10.4 wt%). Under optimized conditions [[Ni] = 5 mu mol, 30 degrees C, oligomerization time = 20 min, 20 bar ethylene, MAO as cocatalyst (500 equiv)], precatalyst Ni2 led to TOF = 63.2 x 10(3) mol(C2H4)center dot(mol(Ni)(-1) h(-1)) and 75.2 wt% selectivity for 1-butene. (C) 2016 Elsevier B.V. All rights reserved.