Chemisorption pathways and catalytic olefin polymerization properties of group 4 mono- and binuclear constrained geometry complexes on highly acidic sulfated alumina

Linda A. Williams, Tobin J. Marks

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Mono- and binuclear "constrained-geometry catalyst" (CGC) group 4 hydrocarbyls Me 2Si(Me 5C 5)-( tBuN)ZrMe 2 [CGCZrMe 2,1], 1-Me 2Si(3-ethylindenyl)( tBuN)ZrMe 2 [EICGCZrMe 2; Zr 1, 2], (μ-CH 2CH 2-3,3) {(η 5-indenyl)[1-Me 2Si-( tBuN)](ZrMe 2)} 2 [EBICGC(ZrMe 2) 2, Zr 2, 3], and (μ-CH 2CH 2-3,3){η 5- indenyl)[1-Me 2Si-( tBuN)](TiMe 2)} 2 [EBICGC(TiMe 2) 2, Ti 2, 4] undergo rapid chemisorption on highly Brønsted acidic sulfated alumina (A1S) surfaces. 13C CPMAS NMR spectroscopy of the chemisorbed 13C aH 3-enriched complexes EICGCZr 13Me 2/AlS (2*/AlS) and EBICGC(Zr 13Me 2) 2/AlS (3*/AlS) reveals that chemisorption involves two processes, M-C σ-bond protonolysis at the strong surface Brønsted acid sites and heterolytic M-C scission with methide transfer to strong surface Lewis acid sites, forming similar "cation-like" electrophilic organo-group 4 complexes such as EICGCM 13Me +. Relative rates of ethylene homopolymerization mediated by the catalysts prepared via chemisorption on A1S are 4/A1S > 2/A1S > 3/A1S > 1/A1S, for ethylene polymerization at 75 psi ethylene and 25 °C. Ethylene/1-hexene eopolymerizations mediated by the same set of catalysts display relative polymerization rates of 4/A1S > 3/A1S > 2/A1S > 1/A1S, for copolymerizations at 75 psi ethylene, 0.8 M 1-hexene, and 25 °C.

Original languageEnglish
Pages (from-to)2053-2061
Number of pages9
Issue number7
Publication statusPublished - Apr 13 2009


ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

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