4,4′-Difluorobenzhydryl-modified bis(imino)-pyridyliron() 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-FC 6 H 4 ) 2 CH 2 -4- t -BuC 6 H 2 )}-6-(CMeNAr)C 5 H 3 N] FeCl 2 (Ar = 2,6-Me 2 C 6 H 3 Fe1 , 2,6-Et 2 C 6 H 3 Fe2 , 2,6-i-Pr 2 C 6 H 3 Fe3 , 2,4,6-Me 3 C 6 H 2 Fe4 , 2,6-Et-4-MeC 6 H 2 Fe5 and 2,6-(4-FC 6 H 4 ) 2 CH 2 -4- t -BuC 6 H 2 Fe6 ), were synthesized in good yields. All iron complexes were characterized by 1 H/ 19 F 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 × 10 6 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 × 10 6 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. Extremely highly active and thermal-stable bis(imino)pyridine-iron precatalysts appended with ( p -FPh) 2 CH groups were achieved in ethylene polymerization for highly linear polyethylenes with narrow distributions.