Vinyl polymerization of norbornene with nickel catalysts bearing [N,N] six-membered chelate ring: Important influence of ligand structure on activity

Norbornene polymerizations with nickel complexes bearing [N,N] six-membered chelate ring activated with methylaluminoxane were investigated. The influence of ligand structure such as β-diimine, β-diketiminate, fluorinated β-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 Al/Ni ratio on norbornene polymerization with nickel catalysts bearing β-diimine, β-diketiminate, and fluorinated β-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.

Graphical abstractVinyl polymerizations of norbornene with nickel complexes bearing [N,N] six-membered chelate ring activated with methylaluminoxane are investigated. The bulky steric hindrance of nickel complexes resulted in higher catalytic activity; ligands led to different electrophilicity of the nickel metal center, and a relatively positive nickel metal center would exhibit high catalytic activities for norbornene polymerization.Figure optionsDownload full-size imageDownload as PowerPoint slide