Naphthalenyl‐Substituted α,α′‐Bisimino‐2,3 : 5,6‐Bis(pentamethylene)pyridines as Thermally Robust Supports for Iron Ethylene Polymerization Catalysts

Abstract

AbstractSix examples of N,N,N‐chelated iron(II) chloride complex, [2,3 : 5,6‐{C4H8C(NAr)}2C5H3N]FeCl2 (Ar=1‐C10H7 Fe1, 2‐Me‐1‐C10H6 Fe2, 2‐(CHMePh)‐1‐C10H6 Fe3, 2‐Cl‐1‐C10H6 Fe4, 4‐Br‐1‐C10H6 Fe5, 4‐NO2‐1‐C10H6 Fe6), differing in the steric/electronic properties of the substituents appended to the N‐naphthalen‐1‐yl groups, have been synthesized in reasonable yield via a facile one‐pot route. The molecular structure of five‐coordinate Fe3 emphasizes the steric hindrance imposed on the iron center by the CHMePh‐substituted bicyclic aromatic groups. With either methylaluminoxane (MAO) or modified methylaluminoxane (MMAO) as activator, the complexes displayed a wide range in catalytic activities for ethylene polymerization with the order for MMAO being: Fe3>Fe2≫Fe1>Fe4≫Fe5 while Fe6 was almost inactive. In particular, Fe3/MMAO exhibited exceptionally high activity at 70 °C (up to 15.7×106 g (PE) mol−1 (Fe) h−1) affording low molecular weight (2.97 kg mol−1) polyethylene of high linearity and narrow dispersity (Mw/Mn=1.38). Moreover, the same catalyst displayed excellent thermostability by maintaining high activity at 90 °C (up to 9.26×106 g (PE) mol−1 (Fe) h−1). Similar activity trends were observed with MAO though the catalysts were in general less active but formed distinctly higher molecular weight polyethylene.