Fluoroanions and cations in the HF–SbF5 superacid system. A 19F and 1H NMR study

The ionic composition of the HF–SbF5 superacid system has been investigated by 1H and 19F high field NMR. The anionic distribution over the whole composition range could be directly calculated from the 19F NMR spectra. The cationic distribution was then estimated on the basis of charge balance. When the concentration of SbF5 in HF was higher than 20 mol%, increasing amounts of nonassociated SbF5 appeared. This change in composition can be linked to the change in reactivity of the superacid system in the activation process of small alkanes.