Alkyl rearrangement processes in organozirconium complexes. Observation of internal alkyl complexes during hydrozirconation

Paul J. Chirik, Michael W. Day, Jay A. Labinger, John E. Bercaw

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53 Scopus citations

Abstract

Isotopically labeled alkyl zirconocene complexes of the form (CpRn)2Zr(CH2CDR′2)(X) (CpRn = alkyl-substituted cyclopentadienyl; R′ = H, alkyl group; X = H, D, Me) undergo isomerization of the alkyl ligand as well as exchange with free olefin in solution under ambient conditions. Increasing the substitution on the Cp ring results in slower isomerization reactions, but these steric effects are small. In contrast, changing X has a very large effect on the rate of isomerization. Pure σ-bonding ligands such as methyl and hydride promote rapid isomerization, whereas π-donor ligands inhibit β-H elimination and hence alkyl isomerization. For (η-C5H5)2Zr(R)(Cl), internal alkyl complexes have been observed for the first time. The rate of isomerization depends on the length of the alkyl group: longer alkyl chains (heptyl, hexyl) isomerize faster than shorter chains (butyl). The transient intermediate species have been identified by a combination of isotopic labeling and 1H, 2H, and 13C NMR experiments. The solid-state structure of the zirconocene cyclopentyl chloride complex, Cp2Zr(cyclo-C5H9)(Cl), has been determined by X-ray diffraction.

Original languageEnglish (US)
Pages (from-to)10308-10317
Number of pages10
JournalJournal of the American Chemical Society
Volume121
Issue number44
DOIs
StatePublished - Nov 10 1999
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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