Fusing Carbocycles of Inequivalent Ring Size to a Bis(imino)pyridine-Iron Ethylene Polymerization Catalyst: Distinctive Effects on Activity PE Molecular Weight and Dispersity

摘要

The 4,6-bis(arylimino)-1,2,3,7,8,9,10-heptahydrocyclohepta[ ]quinoline-iron(II) chlorides (aryl = 2,6-Me C H ; 2,6-Et C H ; 2,6- -Pr C H ; 2,4,6-Me C H ; and 2,6-Et -4-Me C H ) have been prepared in good yield by a straightforward one-pot reaction of 2,3,7,8,9,10-hexahydro-1H-cyclohepta[ ]quinoline-4,6-dione, FeCl ·4H O, and the appropriate aniline in acetic acid. All ferrous complexes have been characterized by elemental analysis and FT-IR spectroscopy. In addition, the structure of has been determined by single crystal X-ray diffraction, which showed the iron center to adopt a distorted square pyramidal geometry with the saturated sections of the fused six- and seven-membered carbocycles to be -configured. In combination with either MAO or MMAO, – exhibited exceptionally high activities for ethylene polymerization (up to 15.86 × 10  g(PE) mol  (Fe) h at 40°C (MMAO) and 9.60 × 10  g(PE) mol  (Fe) h at 60°C (MAO)) and produced highly linear polyethylene (HLPE, ≥ 128°C) with a wide range in molecular weights; in general, the MMAO-promoted polymerizations were more active. Irrespective of the cocatalyst employed, the 2,6-Me -substituted and proved the most active while the more sterically hindered 2,6- -Pr the least but afforded the highest molecular weight polyethylene ( 65.6–72.6 kg mol ). Multinuclear NMR spectroscopic analysis of the polymer formed using /MMAO at 40°C showed a preference for fully saturated chain ends with a broad bimodal distribution a feature of the GPC trace ( / = 13.4). By contrast, using /MAO at 60°C a vinyl-terminated polymer of lower molecular weight ( = 14.2 kg mol ) was identified that exhibited a unimodal distribution ( / = 3.8). Moreover, the amount of aluminoxane cocatalyst employed, temperature, and run time were also found to be influential on the modality of the polymer.