Nitrosonium
Template:Short description Template:Chembox
The nitrosonium ion is Template:Chem2, 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: Template:Chem2, Template:Chem2 (nitrosylsulfuric acid, more descriptively written Template:Chem2) and Template:Chem2. The [[perchlorate|Template:Chem2]] and [[tetrafluoroborate|Template:Chem2]] salts are slightly soluble in acetonitrile Template:Chem2. NOBF4 can be purified by sublimation at 200–250 °C and Template:Convert.[1]
Synthesis and spectroscopy
Template:Chem2 is isoelectronic with CO, [[cyanide|Template:Chem2]] and [[dinitrogen|Template:Chem2]]. It arises via protonation of nitrous acid:
- HONO + H+ Template:Eqm NO+ + H2O
In its infrared spectrum of its salts, νNO is a strong peak in the range 2150-2400 cm−1.[2]
Chemical properties
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Hydrolysis
Template:Chem2 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
Template:Chem2 reacts with aryl amines, Template:Chem2, to give diazonium salts, Template:Chem2. The resulting diazonium group is easily displaced (unlike the amino group) by a variety of nucleophiles.
As an oxidizing agent
Template:Chem2, e.g. as Template:Chem2, is a strong oxidizing agent:[3]
- vs. ferrocene/ferrocenium, Template:Chem2 in Template:Chem2 solution has a redox potential of 1.00 V (or 1.46–1.48 V vs SCE),
- vs. ferrocene/ferrocenium, Template:Chem2 in Template:Chem2 solution has a redox potential of 0.87 V vs. (or 1.27–1.25 V vs SCE).
In organic chemistry, it selectively cleaves ethers and oximes, and couples diarylamines.[4]
Template:Chem2 is a convenient oxidant because the byproduct NO is a gas, which can be swept from the reaction using a stream of Template:Chem2. Upon contact with air, NO forms Template:Chem2, which can cause secondary reactions if it is not removed. Template:Chem2 is readily detectable by its characteristic orange color.
Nitrosylation of arenes
Electron-rich arenes are nitrosylated using NOBF4.[5] One example involves anisole:
- CH3OC6H5 + NOBF4 → CH3OC6H4NO + HBF4
Nitrosonium, Template:Chem2, is sometimes confused with nitronium, NOTemplate:Su, 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 (nitric acid) and the latter from a weak acid (nitrous acid).
As a source of nitrosyl complexes
Script error: No such module "Labelled list hatnote". NOBF4 reacts with some metal carbonyl complexes to yield related metal nitrosyl complexes.[6] In some cases, [NO]+ does not bind the metal nucleophile but acts as an oxidant.
- (C6Et6)Cr(CO)3 + NOBF4 → [(C6Et6)Cr(CO)2(NO)]BF4 + CO
See also
- Nitronium (NO2+)
- Nitric oxide (NO)
References
Template:Nitric oxide signaling Template:Nitrogen compounds
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- ↑ T. W. Hayton, P. Legzdins, W. B. Sharp. "Coordination and Organometallic Chemistry of Metal-NO Complexes". Chemical Reviews 2002, volume 102, pp. 935–991.