Corresponding cyclic perfluoroaliphaticdisulfonimide ammonium salts are conveniently prepared by the introduction of anhydrous gaseous ammonia into a solution of the precursor perfluoroaliphaticdisulfonyl fluoride in an inert solvent.
About four moles of ammonia per mole of perfluoroaliphaticdisulfonyl fluoride is required to achieve good yields.