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

Authors
Journal
Inorganica Chimica Acta
0020-1693
Publisher
Elsevier
Publication Date
Volume
361
Issue
7
Identifiers
DOI: 10.1016/j.ica.2007.09.039
Keywords
  • Iron
  • Binuclear Catalysts
  • Bis(Imino)Pyridyl Complexes
  • Bimodal Polyethylene
  • Ethylene Polymerization

Abstract

Abstract Three novel methylene bridged binuclear iron(II) complexes: { [ 2 , 6 -R 2 -C 6 H 3 N C ( CH 3 ) C 5 H 3 N ( CH 3 ) C N ( 3 , 5 -R 2 ′ ) C 6 H 2 -CH 2 - ( 3 , 5 -R 2 ′ ) C 6 H 2 N C ( CH 3 ) C 5 H 3 N ( CH 3 ) C N ( 2 , 6 -R 2 ) C 6 H 3 ] [ FeCl 2 ] 2 (R,R′ = i-C 3H 7 ( 6); R = i-C 3H 7, R′ = CH 3 ( 7); R,R′ = CH 3 ( 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 {[ArN C(Me)C 5H 3N(Me)C NAr′]FeCl 2 (Ar,Ar′ = 2,6-C 6H 3- i-Pr ( 9); Ar = 2,6-C 6H 3- i-Pr 2, Ar′ = 2,6-C 6H 3–Me 2 ( 10); Ar,Ar′ = 2,6-C 6H 3–Me 2 ( 11))}. The molecular weight ( M w) of PE produced by 7 and 8 are in the range 13.2–46.0 × 10 4 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.

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