A series of nickel halides bearing 2,4-di-t-butyl-6-(quinolin-8-yliminomethyl) phenolate ligands was synthesized and characterized by IR spectroscopy and elemental analysis. Molecular structures of C1 (R = H, X = Br) and C2 (R = H, X = Cl) were further confirmed by single-crystal X-ray crystallographic studies, and revealed a distorted square planar geometry at nickel. Upon activation with diethylaluminum chloride (Et2AlCl), all nickel pre-catalysts displayed good catalytic activity [up to 9.3 × 105 g mol−1 (Ni) h−1] for ethylene oligomerization with major dimerization. In the presence of methylaluminoxane (MAO), the nickel complex C1 was capable of ethylene polymerization under 3 MPa, and produced polyethylene products with narrow polydispersity (1.16–1.73) and molecular weights in the range of 2.6–4.95 kg/mol.