A series of bis(benzimidazolyl)amine and bis(benzimidazolyl)pyridine ligands and their respective nickel(II) dibromide complexes were synthesized and fully characterized. After activation of the nickel complexes with ethylaluminum sesquichloride showed productivity in excess of 10(6) (g-oligomer)(mol-Ni)(-1)h(-1)bar(-1) towards ethylene oligomerization, producing butenes as major products. The bis(benzimidazolyl)pyridine nickel complexes showed higher activity and dimerization selectivity than corresponding bis(benzimidazolyl)amine nickel complexes.