Vinyl polymerization of norbornene by nickel(II) complexes bearing β‐diketiminate ligands

Norbornene polymerizations were carried out using nickel(II) bromide complexes CH{C(R)NAr}2NiBr (1, R = CH3, Ar = 2, 6 − iPr2C6H3; 2, R = CH3, Ar = 2, 6‐Me2C6H3; 3, R = CF3, Ar = 2, 6 − iPr2C6H3; 4, R = CF3, Ar = 2, 6‐Me2C6H3) in the presence of methylaluminoxane. Compound 3 is the most active norbornene polymerization catalyst of all the nickel complexes tested. The activity of theses catalysts increases with increases in steric bulk of the substituents on the aryl rings. The electronic nature of the ligand backbone also affects the activity. The resulting polynorbornenes are vinyl type by IR and NMR analyses.