Thirteen mono- and three bisformazans containing one system of azahydrazone bonds have been synthesized, as well as mono- and binuclear complexes on their basis. The kinetic features of ethylene oligomerization in the presence of catalytic systems on the basis of AlEtCl2-activated Ni(II) formazanates differing in composition and structure have been studied. The structures of the mono- and binuclear complexes differ by substituents in the formazan ligand, which have an effect on the activity of the systems and the product composition. The catalytic activity of the binuclear complexes is several times below that of mononuclear Ni(II) formazanates.