Insight into Oxide-Bridged Heterobimetallic Al/Zr Olefin Polymerization Catalysts

Cedric Boulho, Harmen S. Zijlstra, Alexander Hofmann, Peter H. M. Budzelaar, Sjoerd Harder*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

6 Citations (Scopus)
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Abstract

Reaction of (TBBP)AlMeTHF with [Cp*Zr-2(Me)OH] gave [(TBBP)Al(THF)-O-Zr(Me)Cp*(2)] (TBBP=3,3',5,5'-tetra-tBu-2,2'-biphenolato). Reaction of [DIPPnacnacAl(Me)-O-Zr(Me)Cp-2] with [PhMe2NH](+)[B(C6F5)(4)](-) gave a cationic Al/Zr complex that could be structurally characterized as its THF adduct [(DIPPnacnac)Al(Me)-O-Zr(THF)Cp-2](+)[B(C6F5)(4)](-) (DIPPnacnac=HC[(Me)C=N(2,6-iPr(2)-C6H3)](2)). The first complex polymerizes ethene in the presence of an alkylaluminum scavenger but in the absence of methylalumoxane (MAO). The adduct cation is inactive under these conditions. Theoretical calculations show very high energy barriers (G=40-47kcalmol(-1)) for ethene insertion with a bridged AlOZr catalyst. This is due to an unfavorable six-membered-ring transition state, in which the methyl group bridges the metal and ethene with an obtuse metal-Me-C angle that prevents synchronized bond-breaking and making. A more-likely pathway is dissociation of the Al-O-Zr complex into an aluminate and the active polymerization catalyst [Cp*2ZrMe](+).
Original languageEnglish
Pages (from-to)17450-17459
Number of pages10
JournalChemistry
Volume22
Issue number48
DOIs
Publication statusPublished - 21-Nov-2016

Keywords

  • alkene polymerization
  • aluminum
  • bimetallic catalysis
  • synthetic methods
  • zirconium
  • MONOMER-DIMER EQUILIBRIA
  • LIQUID ALUMINUM ALKYLS
  • STRUCTURAL-CHARACTERIZATION
  • HOMOGENEOUS CATALYSTS
  • TRANSITION-ELEMENTS
  • TERT-BUTYLALUMINUM
  • LIGANDS
  • DENSITY
  • COMPLEXES
  • TRIETHYLALUMINUM

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