Norbornene polymerizations with nickel complexes bearing [N,N] six-membered chelate ring activated with methylaluminoxane were investigated. The influence of ligand structure such as beta-diimine, beta-diketiminate, fluorinated beta-diketiminate, and anilido-imine ligand on catalytic activities for norbornene polymerization was evaluated in detail. Ligands led to different electrophilicity of the nickel metal center, and a relatively positive nickel. metal center would result in high catalytic activities for norbornene polymerization. The influences of polymerization temperature and A1/Ni ratio on norbornene polymerization with nickel catalysts bearing beta-diimine, beta-diketiminate, and fluorinated beta-diketiminate ligands were also examined. All of the obtained polymers catalyzed by these nickel catalysts bearing [N,N] ligand are vinylic addition polynorbornenes with different molecular weights. (C) 2007 Elsevier B.V. All rights reserved.