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1998 (1)
1979 (2)
1Author    Franz Kalchsclimid, Erwin MayerRequires cookie*
 Title    Bildung von Alkylcarbenium-Ionen im System Aluminium-(Gallium-)halogenid/Halogenwasserstoff Formation of Alkylcarbenium Ions in the System Aluminium (Gallium) Halide/ Hydrogen Halide  
 Abstract    The tert-butyl cation is formed in the reaction of tert-BuCl with AICI3 or GaCl3 in anhydrous liquid HCl as a solvent, or of £ert-BuBr with AlBr3 in HBr. At — 30 °C solutions of [C(CH3)3 + ] are stable. At room temperature very slow decomposition occurs over months. In the systems BCI3/HCI, InCl3/HCl and BBr3/HBr no formation of [C(CH3)3+] from the corresponding £erZ-butyl halide was observed. The tert-'Amy\ cation can be stabilized only in AlBr3/HBr. The iso-propyl cation is not stable in any of the systems investigated. The ability of the Lewis acids employed to form carbenium ions corresponds with their catalytic activity in Friedel-Crafts alkylations. 
  Reference    Z. Naturforsch. 34b, 548—552 (1979); eingegangen am 5. Januar 1979 
  Published    1979 
  Keywords    Alkylcarbenium Ions, ferZ-Butyl Cation, Aluminium Halides, Hydrogen Halides, NMR 
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 TEI-XML for    default:Reihe_B/34/ZNB-1979-34b-0548.pdf 
 Identifier    ZNB-1979-34b-0548 
 Volume    34 
2Author    Peter Brüggeller, Erwin MayerRequires cookie*
 Title    Dimethylhalonium-Ionen in Aluminiumhalogenid/Methylhalogenid-Lösungen Dimethylhalonium-Ions in Aluminium Halide/Methyl Halide Solutions  
 Abstract    Evidence for the formation of (CH3)2Br+ and (CH3)2l + in CH3Br and CH3I solutions saturated with AlBr3 comes from the appearance of a second singlet in the iH NMR spectrum. The (CH3)2Br+ ion is formed at —40 °C to about 5 mol%, the (CH3)2l + ion at —12 °C with 50 mol% yield. At higher temperatures the concentration of the halonium ions decreases rapidly. The (CH3)2Br+ ion is not detectable at room temperature, the concentra-tion of (CH3)2l + decreases to about 30 mol%. Dilution of the saturated solutions with methyl halide also reduces the halonium ion concentration. An AlBrs/CHsBr solution with a molar ratio of 1:3 at —40 °C shows no sign of (CH3)2Br+ formation in the X H NMR spectrum. Both effects are best explained by formation of dimethylhalonium ions from the adduct CH3X-AIX3 and by dependence of adduct concentration on temperature and dilution. Exchange of (CH3)2Br+ and (CH3)2l + with methyl halide is slow on the NMR time scale at low temperatures similar to the results in SbFs/SC^. The ] H NMR singlets of (CH3)2Br+ and (CH3)2l + are shifted to lower field by 1.32 and 1.68 ppm in comparison with the chemical shifts in SbFs/SC^ solution. 
  Reference    Z. Naturforsch. 34b, 896—899 (1979); eingegangen am 5. März 1979 
  Published    1979 
  Keywords    Dimethylbromonium Ion, Dimethyliodonium Ion, iH NMR, Aluminium Halides, Methyl Halides 
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 TEI-XML for    default:Reihe_B/34/ZNB-1979-34b-0896.pdf 
 Identifier    ZNB-1979-34b-0896 
 Volume    34 
3Author    Marcus Sigl, Annette Schier, Hubert SchmidbaurRequires cookie*
 Title    Lewis Acid Catalyzed Z to E Isomerization of 1,2-Bis(diphenyl- phosphino)ethene  
 Abstract    Z-l,2-Bis(diphenylphosphino)ethene, cis-Ph2PCH=CHPPh2, forms 1:2 adducts with GaBn and GaL, the former of which has been identified in an X-ray diffraction study as the complex of the isomerized ligand, E-Ph2PCH=CHPPh2. The GaL 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)2lnBr2]+ [InBr4]_ in which the cation contains the original cis-ligand. With Inl^ 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 Inl3 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 AIX3 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. 
  Reference    Z. Naturforsch. 53b, 1301—1306 (1998); received August 13 1998 
  Published    1998 
  Keywords    Z/E Isomerization, Phosphino-Ethenes, Lewis Acid Catalysis, Gallium Halides, Aluminium Halides, Indium Halides 
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 TEI-XML for    default:Reihe_B/53/ZNB-1998-53b-1301.pdf 
 Identifier    ZNB-1998-53b-1301 
 Volume    53