Nitrosonium
The nitrosonium ion is, in which the nitrogen atom is bonded to an oxygen atom with a bond order of 3, and the overall diatomic species bears a positive charge. It can be viewed as nitric oxide with one electron removed. This ion is usually obtained as the following salts:, and. The [perchlorate|] and [tetrafluoroborate|] salts are slightly soluble in acetonitrile. NOBF4 can be purified by sublimation at 200–250 °C and.
Synthesis and spectroscopy
is isoelectronic with CO, [cyanide|] and [dinitrogen|]. It arises via protonation of nitrous acid:In its infrared spectrum of its salts, νNO is a strong peak in the range 2150–2400 cm−1.
Chemical properties
Hydrolysis
reacts readily with water to form nitrous acid:For this reason, nitrosonium compounds must be protected from water or even moist air. With base, the reaction generates nitrite:
As a diazotizing agent
reacts with aryl amines,, to give diazonium salts,. The resulting diazonium group is easily displaced by a variety of nucleophiles.As an oxidizing agent
, e.g. as, is a strong oxidizing agent:- vs. ferrocene/ferrocenium, in solution has a redox potential of 1.00 V,
- vs. ferrocene/ferrocenium, in solution has a redox potential of 0.87 V vs..
is a convenient oxidant because the byproduct NO is a gas, which can be swept from the reaction using a stream of. Upon contact with air, NO forms, which can cause secondary reactions if it is not removed. is readily detectable by its characteristic orange color.
Nitrosylation of arenes
Electron-rich arenes are nitrosylated using NOBF4. One example involves anisole:Nitrosonium,, is sometimes confused with nitronium, NO, the active agent in nitrations. These species are quite different, however. Nitronium is a more potent electrophile than is nitrosonium, as anticipated by the fact that the former is derived from a strong acid and the latter from a weak acid.