219726-20-2Relevant academic research and scientific papers
Lewis Acid Catalyzed Z to E Isomerization of 1,2-Bis(diphenylphosphino)ethene
Sigl, Marcus,Schier, Annette,Schmidbaur, Hubert
, p. 1301 - 1306 (1998)
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.
