Carbonium ion salts. XIII. Stable triarylcarbonium pentahalostannate(IV) salts

Article abstract of DOI:10.1021/ic50075a007

Certain triarylmethyl halides form stable 1:1 adducts with stannic halide; facile hydride-transfer reactions, electronic spectra, and a combination of X-ray, infrared, and M?ssbauer effect data demonstrate that these are salts of triarylcarbonium ions and monomeric trigonal-bipyramidal pentahalostannate(IV) ions. The formation of these salts is not kinetically controlled, as the stoichiometry of the solid is not changed by use of excess halide, equilibration in strongly ionizing solvents, or preparation from preformed hexahalostannate(IV) ions. Variable-temperature nmr equilibrium measurements of the ionization of triphenylmethyl chloride by pentachlorostannate(IV) ion in méthylène chloride yield the values ΔG° = 1.85 kcal/mol, ΔH° = -9.56 kcal/mol, and ΔS° = -38.6 eu at 25° for this reaction and allow the prediction of the stability of other triarylcarbonium ion pentachlorostannate(IV) salts. The preparations and interconversions of a number of such salts and their bromide analogs are described.