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Halogenated Carboxonium Salts:  Preparation and Structural Analysis

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journal contribution
posted on 09.02.1999, 00:00 by Rolf Minkwitz, Stefan Reinemann, Oliver Blecher, Hans Hartl, Irene Brüdgam
We have studied the preparation and isolation of the halogenated alkylidene oxonium salts CH3OCHX+MF6- (X = Cl, F; M = As, Sb). Addition of dichloromethylmethylether at −78 °C to the superacidic media HF/MF5 resulted in the formation of the chlorine compounds CH3OCHCl+MF6-, whereas at −65 °C the fluorinated salts CH3OCHF+MF6- are formed by a chlorine/fluorine exchange. The salts are characterized by their low-temperature IR and Raman spectra. Additionally, the crystal structures of the hexafluoroantimonates are presented. The structures of the cations turned out to be different in some points. The salt CH3OCHF+SbF6- crystallizes in the monoclinic space group P21/c with 4 molecules in the unit cell and a = 9.942(2), b = 7.454(2), and c = 10.297(3) Å; β = 111.27(2)°. The salt CH3OCHCl+SbF6- crystallizes in the monoclinic space group P21/c with 4 formula in the unit cell and a = 5.970(3), b = 12.019(5), and c = 10.994(5) Å; β = 92.59(3)°.