The derivatives of 4,5-diazafluorene-9-one-benzoylhydrazone (1-4) and 2-pyridine-carboxaldehyde-benzoylhydrazone (5-9) were prepared. The compounds 1-4 reacted with Ni(Ac)(2)(.)4H(2)O to form diaquabis [4,5-diazafluorene-9-one-benzoylhydrazone] nickel (II) (10-13), while the compounds 5-9 reacted with (DME)NiBr2 to form bis[N-(pyridine-2-carboxaldehyde-benzoylhydrazone)] nickel (II) dibromide (14-18), respectively. All ligands and complexes were characterized by elemental analysis and spectroscopic analysis, along with the X-ray single crystal diffraction techniques for 10, 13 and 14. The nickel (II) centers are six-coordinated with two corresponding ligands and two coordinated solvents for 10-13, while the geometry around the nickel atom of 14-18 is distorted octahedron with two ligands and two bromides. Activated with methylaluminoxane, all nickel complexes show good activities for vinyl polymerization of norbornene and considerable activities for ethylene oligomerization at ambient pressure. By using 10, the influence of reaction conditions was carefully examined on the catalytic behavior of vinyl polymerization of norbornene. The catalytic conditions were varied to investigate their effects on activity of ethylene oligomerization. The resulting poly(norbornene)s were characterized by IR. H-1 NMR, TGA, DSC and the viscosity measurement. (c) 2005 Elsevier B.V. All rights reserved.