A F-19 nuclear magnetic resonance study of the conjugate Bronsted-Lewis superacid HSO3F-SbF5. Part 1

The Bronsted-Lewis superacid HSO3F-SbF5 or "magic acid" is re-investigated by modern F-19 NMR methods over a wide concentration range. The system is found to be considerably more complex than had been assumed previously. A,total of 13 different anions are identified of which only five have previously been identified in magic acid. With increasing SbF5 contents the concentration of monomeric anions like [SbF6](-), [SbF5(SO3F)](-), cis- and trans-[SbF4(SO3F)(2)](-), and mer-[SbF3(SO3F)(3)](-) gradually decreases. Except for [Sb2F11](-), which is present in very small concentrations only the formation of oligomers involves exclusively mu-fluorosulfato bridges. In addition to donor (SO3F)(-) and acceptor (SbF5) complex formation to give [SbF5(SO3F)](-) and possibly ligand redistribution, the solvolysis of SbF5 or SbF4(SO3F) in HSO3F appears to be the principal formation reaction for polyfluorosulfatofluoroantimonate(V) anions. In glass (NMR tubes) the solvolysis product HF is converted to the oxonium ion [H3O](+), which has previously been identified by H-1 NMR and structurally characterized as [H3O][Sb2F11] by us.