α-Diimine nickel complexes bearing axially bulky terphenyl and equatorially bulky dibenzobarrelene groups: synthesis, characterization and olefin polymerization studies

The axial and equatorial bulkiness in the α-diimine Ni/Pd type complexes are two crucial parameters that govern the catalytic activity, the thermostability of precatalysts and the molecular weight as well as chain structure of the resulting polymers. In this contribution, we report the synthesis and characterization of a new family of α-diimine nickel complexes which bear the axially bulky terphenyl group and the equatorially bulky dibenzobarrelene group, and upon activation with MAO, these complexes not only displayed high activities towards ethylene polymerization, but also could give rise to ultra-high-molecular-weight polyethylenes (Mw as high as 174.8 × 105) due to the efficient retardation of chain transfer reactions for ethylene polymerization. Mechanical studies revealed that the resultant polyethylenes showed typical elastomeric properties.