The class of chemical salts containing nitronium cation (NO2+) are called nitronium salts. Nitronium salts are excellent nitrating agents and are superior to the mixed acids or other nitrating agents since the attacking species of nitration, nitronium cation (NO2+) is readily available in the nitronium salts before the interaction with the substrate.
Nitronium tetrafluoroborate (NO2+BF4-) and nitronium hexafluorophosphate (NO2+PF6-) are some of the most frequently used nitronium salts for nitration of organic compounds. These salts are extremely active for the nitration of aromatic compounds and will give high yield under mild conditions. Nitronium salts have also been used in the nitration of aliphatic compounds. Nitronium tetrafluoroborate is a versatile nitrating agent for nitrogen compounds. When reacted with secondary aliphatic amines, aryl aliphatic amine, carbamate ester, diacyl amine and primary amides, nitronium tetrafluoroborate gives corresponding N-nitro derivatives. Nitronium tetrafluoroborate is also used in the nitration of alkylsilanes to give corresponding nitroalkanes.