4,4'-Difluorobenzhydryl-modified bis(imino)-pyridyliron(ii) chlorides as thermally stable precatalysts for strictly linear polyethylenes with narrow dispersities.

The 4,4'-difluorobenzhydryl-modified bis(imino)pyridylferrous chlorides, [2-{CMeN(2,6-(4-FC6H4)2CH2-4-t-BuC6H2)}-6-(CMeNAr)C5H3N] FeCl2 (Ar = 2,6-Me2C6H3Fe1, 2,6-Et2C6H3Fe2, 2,6-i-Pr2C6H3Fe3, 2,4,6-Me3C6H2Fe4, 2,6-Et-4-MeC6H2Fe5 and 2,6-(4-FC6H4)2CH2-4-t-BuC6H2Fe6), were synthesized in good yields. All iron complexes were characterized by 1H/19F NMR and elemental analysis, and the molecular structures of representative complexes Fe1 and Fe6 were determined by single crystal X-ray diffraction, which revealed a slightly distorted square pyramid around the iron center. Activated with either MAO or MMAO, Fe1-Fe5 exhibited very high activities (up to 17.2 × 106 g (PE) mol-1 (Fe) h-1 for Fe1/MMAO) toward ethylene polymerization, producing highly linear polyethylenes with narrow dispersities as required by industry and value added PEs. Importantly, the Fe1/MAO maintained an activity of 9.5 × 106 g (PE) mol-1 (Fe) h-1 at 100 °C of operating temperature, making the catalytic system suitable for practical application. Simulation quantitatively revealed the mechanism of the enhanced catalytic performance from the electronic and steric point of view.