The nickel catalysts for ethylene oligomerization and polymerization are of special relevance to catalysis

because of the easy synthesis and various catalytic properties influenced by the characteristics of the attached ligands. Recent progress of late transition metal complexes as catalysts has led to a renaissance in designing novel catalysts for polyolefins beyond the famous SHOP process. The nickel catalysts are interested of the varieties of complexes containing different ligands

which are coordinated with nickel center as the bidentate and tridentate ligands. In contract to the important set of hetereogeneous catalysts

the homogeneous catalyst is a small share for polyolefins

however

the well_defined complexes affect the microstructure of their products. The properties of polyethylene can be affected with adaptation of ligands coordinating to nickel center

so do the oligomers obtained with nickel complexes. Attracted to chemists

auxiliary ligand can improve the catalytic activity in one order of magnitude. In addition to the fast catalytic reaction

the active center can be confirmed through isolating the intermediate which produce the reliable catalytic activity. In the chapter

the development and progress of nickel complexes as catalysts for ethylene oligomerization and polymerization are discussed

and their advantage and disadvantage are also listed with future potentials in academic research and industrial applications.