NitrosylIon

The nitrosyl ion, also called the nitrosonium ion, is the cation NO+. It is the positively charged form of nitrosyl and is commonly described as a linear diatomic species, often represented as N≡O+. In salts, NO+ is stabilized by weakly coordinating anions, and the ion behaves as a strong nitrosating agent.

NO+ is generated in situ in strongly acidic nitrite systems and is available as isolable salts such as nitrosonium tetrafluoroborate [NO+]BF4−, nitrosonium hexafluorophosphate [NO+]PF6−, and related species. These salts are widely used as reagents to transfer the nitrosyl group in chemical synthesis.

Reactivity of the nitrosyl ion centers on its role as a powerful electrophile capable of transferring NO+ to nucleophiles. It readily nitrosates amines to form N-nitrosamines and can nitrosate thiols and other nucleophiles. In coordination chemistry, NO+ binds to transition metals as a nitrosyl ligand, often described as an M–NO+ fragment; such metal nitrosyl complexes are important for studying the chemistry of NO interactions with metals and for understanding electron-counting in organometallic systems.

In practice, NO+-based nitrosation is employed in organic synthesis and inorganic chemistry to introduce the nitrosyl group into substrates. While free NO+ is a reactive and moisture-sensitive species, its salts provide convenient and controllable nitrosylation reagents.

Safety considerations include the strong oxidizing and corrosive nature of NO+-bearing reagents. They are typically moisture sensitive and require appropriate handling, storage, and ventilation to avoid undesired reactions or release of nitrogen oxides.