Cycloocta[b] pyridin-10-one was prepared to form the corresponding imino derivatives, which then reacted with (DME) NiBr2 to form 10-aryliminocycloocta[b] pyridylnickel bromides (Ni1-Ni5). The new compounds were characterized by means of FT-IR spectroscopy as well as elemental analysis and the organic ligands were also analyzed by the NMR measurements. Furthermore, the molecular structure of a representative complex Ni3 was determined by the single crystal X-ray diffraction, indicating the distorted tetrahedral geometry around the nickel atom. Upon the activation with either methylaluminoxane (MAO) or diethylaluminium chloride (Et2AlCl), the title nickel complexes exhibited high activity in ethylene polymerization and produced polyethylene of low molecular weight (1.43-6.78 kg mol 21) and low dispersity (1.7-2.4), which suggests a single-site catalytic system. More importantly, the microstructure of the resultant polyethylene (especially degree of branching) and certain physical properties, such as T-m values, can easily be modulated by selecting the proper substituents within the ligands and adjusting the polymerization conditions. This finding demonstrates that it is plausible to use a single catalyst for synthesizing different types of polyethylene on demand. 10-Aryliminocycloocta[b] pyridylnickel bromides (Ni1-Ni5), upon activation with either MAO or Et2AlCl, exhibited high activity towards ethylene polymerization and produced polyethylenes with low molecular weight (1.43-6.78 kg mol(-1)) and low dispersity (1.7-2.4). (C) 2017 Wiley Periodicals, Inc.