Biphenyl-Bridged 6‑(1-Aryliminoethyl)-2-iminopyridylcobalt Complexes: Synthesis, Characterization, and Ethylene Polymerization Behavior

A series
of biphenyl-bridged 6-(1-aryliminoethyl)-2-iminopyridine
derivatives reacted with cobalt dichloride in dichloromethane/ethanol
to afford the corresponding binuclear cobalt complexes. The cobalt
complexes were characterized by FT-IR spectroscopy and elemental analysis,
and the structure of a representative complex was confirmed by single-crystal
X-ray diffraction. Upon activation with either MAO or MMAO, these
cobalt complexes performed with high activities of up to 1.2 ×
107 g (mol of Co)−1 h–1 in ethylene polymerization, which represents one of the most active
cobalt-based catalytic systems in ethylene reactivity. These biphenyl-bridged
bis­(imino)­pyridylcobalt precatalysts exhibited higher activities than
did their mononuclear bis­(imino)­pyridylcobalt precatalyst counterparts,
and more importantly, the binuclear precatalysts revealed a better
thermal stability and longer lifetimes. The polyethylenes obtained
were characterized by GPC, DSC, and high-temperature NMR spectroscopy
and mostly possessed unimodal and highly linear features.