Methylene bridged binuclear bis(imino)pyridyl iron(II) complexes and their use as catalysts together with Al(i-Bu)3 for ethylene polymerization

Three novel methylene bridged binuclear iron(II) complexes: {[2,6-R2-C6H3NC(CH3)C5H3N(CH3)CN(3,5-R2′)C6H2-CH2-(3,5-R2′)C6H2NC(CH3)C5H3N(CH3)CN(2,6-R2)C6H3][FeCl2]2(R,R′ = i-C3H7 (6); R = i-C3H7, R′ = CH3 (7); R,R′ = CH3 (8))} have been synthesized. Activated by Al(i-Bu)3, complex 6 shows very poor activity for the polymerization of ethylene at one bar ethylene pressure, whereas, 7 and 8 exhibit much higher activity than mononuclear iron catalysts {[ArNC(Me)C5H3N(Me)CNAr′]FeCl2 (Ar,Ar′ = 2,6-C6H3-i-Pr (9); Ar = 2,6-C6H3-i-Pr2, Ar′ = 2,6-C6H3–Me2 (10); Ar,Ar′ = 2,6-C6H3–Me2 (11))}. The molecular weight (Mw) of PE produced by 7 and 8 are in the range 13.2–46.0 × 104 and much higher than those produced by mononuclear iron catalysts 9 and 10. GPC results demonstrate that 7 and 8 yield PE with a broad/bimodal molecular weight distribution (MWD). In contrast, 9 and 10 yield PE with relatively narrow and unimodal MWD (4.26 and 3.55). Elevating the temperature and Al/Fe molar ratio will narrow the MWD of PE.

Three novel methylene bridged binuclear iron(II) complexes: {[2,6-R2-C6H3NC(CH3)C5H3N(CH3)CN(3,5-R2′)C6H2-CH2-(3,5-R2′)C6H2NC(CH3)C5H3N(CH3)CN(2,6-R2)C6H3][FeCl2]2 (6: R,R′ = i-C3H7; 7: R = i-C3H7, R′ = CH3; 8: R,R′ = CH3)} have been synthesized and employed for ethylene polymerization in the presence of Al(i-Bu)3 (TIBA) as cocatalyst. GPC results demonstrate that 7 and 8 yield PE with a broad, even bimodal molecular weight distribution (MWD).Figure optionsDownload as PowerPoint slide