Fluorinated Sterically Bulky Mononuclear and Binuclear 2-Iminopyridylnickel Halides for Ethylene Polymerization: Effects of Ligand Frameworks and Remote Substituents.

In the present work, four new mono(imino)pyridine ligands, 2-((2,4-bis(bis(4-R-phenyl)methyl)-6-fluorophenylimino)methyl)pyridine (R = H, ; R = OCH, ; R = F, ) and 2-((2-(bis(4-fluorophenyl)methyl)-4-((3-(bis(4-fluorophenyl)methyl)-4-amine-5-fluoro-phenyl)(phenyl)methyl)-6-fluorophenylimino)methyl)pyridine (), have been designed in good yields. Additionally, three novel benzhydryl-bridged bis(imino)pyridine ligands, 2-(2-(bis(4-R-phenyl)methyl)-6-fluoro-phenylimino)pyridine (R = H, ; R = OCH, ; R = F, ), were also prepared for comparison. All these organic compounds have been characterized by FT-IR analysis, H/C NMR spectroscopy, and elemental analysis. The treatment of with nickel halides afforded the corresponding monometallic () and bimetallic () nickel complexes in moderate to good overall yields. Upon activation with methylaluminoxane (MAO), showed the highest activity up to 8.3 × 10 g of polyethylene (PE) (mol of Ni) h among for ethylene polymerization. In all cases, unsaturated PEs with low molecular weights (0.7-13.3 kg mol) were produced effectively. The introduction of remote para-substituents into the benzhydryl groups showed a beneficial effect on catalytic activity with the overall activities following the order of -F > -OCH > -H. In addition, these para-substituents were also found to affect not only the catalytic performance of catalysts but also the branching content of the PE product. Generally, the resultant PE waxes were moderately branched and contained both terminal vinyls (-CH=CH) and internal vinylenes (-CH=CH-) while with different ratios of vinyls to vinylenes. Notably, the polymers produced using -methoxy-substituted /MAO and /MAO possessed the least branching content and uniquely high vinyl contributions.