Lewis Acid Catalyzed Z to E Isomerization of 1,2-Bis(diphenylphosphino)ethene

Marcus Sigl, Annette Schier, Hubert Schmidbaur

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11 Scopus citations

Abstract

Z-1,2-Bis(diphenylphosphino)ethene, cis-Ph2PCH=CHPPh2, forms 1:2 adducts with GaBr3 and GaI3, the former of which has been identified in an X-ray diffraction study as the complex of the isomerized ligand, E-Ph2PCH=CHPPh2. The GaI3 complex is believed to be analogous on the basis of analytical and spectroscopic data. InBr3 affords a 1:1 complex with an ionic structure [(Ph2PCH=CHPPh2)2InBr2]+ [InBr4]- in which the cation contains the original cis-ligand. With InI3 also a 1:1 adduct is obtained, where the metal triiodide unit is attached to only one phosphorus atom of the non-isomerized (cis) ligand in the solid state. There is rapid site exchange of the InI3 unit in chloroform solution as followed by NMR spectroscopy. -The metal halide induced Z/E isomerization of Ph2PCH=CHPPh2 has been studied in various solvents and at variable temperature with stoichiometric and catalytic amounts of AlX3 and GaX3 Lewis-acids. InX3 compounds proved ineffective (X = Cl, Br, I). Anhydrous AlBr3 was found to be most efficient, giving a 90% Z/E conversion in 10 min at 100°C in toluene. A mechanism is proposed which is compatible with the experimental data.

Original languageEnglish
Pages (from-to)1301-1306
Number of pages6
JournalZeitschrift fur Naturforschung - Section B Journal of Chemical Sciences
Volume53
Issue number11
DOIs
StatePublished - Nov 1998
Externally publishedYes

Keywords

  • Aluminium Halides
  • Gallium Halides
  • Indium Halides
  • Lewis Acid Catalysis
  • Phosphino-Ethenes
  • Z/E Isomerization

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