Copolymerization of ethylene/unsaturated alcohols using nickel catalysts: effect of the ligand on the activity and comonomer incorporation

The nickel complexes {bis[N,N′-di(2-t-butylphenyl)imino]acenaphthene} dibromonickel (1-NiBr2) and {bis[N,N′-di(2-phenylphenyl)imino]acenaphthene} dibromonickel (2-NiBr2) were studied in homo-, co- and terpolymerization of ethylene and propylene with polar monomers and the results compared to those previously obtained with another catalyst precursor [bis(N,N′-dimesitylimino)acenaphthene] dibromonickel (3-NiBr2). In order to understand the effect of the ligand in the activity and rate of comonomer incorporation some theoretical studies, using both a semi-empirical molecular orbital method and a density-functional theory model, were performed. Good agreement was found between the computed parameters and the experimental results for the order of homo-polymerization, the differences in polymer molecular weight distribution, and, in some cases, the incorporation of functionalized copolymers in the case of copolymerization, and also on the inhibition effects caused by these copolymers.