Amino-containing α-Diimine Nickel Complexes with Adjustable Electronic Properties and their Effective Use in Forming Highly Branched Polyethylene

A family of ten amino-containing bis(arylimino)acenaphthene-nickel (II) bromide complexes varied in the electronic properties of para-substituents (R = Me, ⁱPr, ^tBu, OMe, Cl, F, NO₂) as well as two amino-free comparators (R = Me, Cl) are synthesized in good yield from their corresponding unsymmetrical N,N’-ligands. All organic compounds are well characterized by different analysis techniques. On activation with Me₂AlCl, all nickel complexes exhibit moderate to high activities with a maximum activity up to 14.19 × 10⁶ g (PE) mol⁻¹ (Ni) h⁻¹ and deliver narrow dispersed polyethylene (PDI: 1.85–2.65) with adjustable molecular weight values (M_w: 5.27–18.49 × 10⁵ g mol⁻¹). The presence of remote fluoro- group and (4-amino-3,5-dimethylphenyl)(phenyl)methyl group has their own unique influence on activity due to their different electronic and steric properties. Nevertheless, the latter with higher steric hindrance results in better thermal stability of the current catalytic system. Moreover, all polyethylene is highly branched and exhibits typical characteristics of thermoplastic elastomers, especially good mechanical properties (εb up to 1175%) and elastic recovery rate (up to 86%).