Nitrosonium

Synthesis and spectroscopy

is isoelectronic with CO, and . It arises via protonation of nitrous acid: :HONO + H+ NO+ + H2O

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 (unlike the amino group) 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 (or 1.46–1.48 V vs SCE),
• vs. ferrocene/ferrocenium, in 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.

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: : CH3OC6H5 + NOBF4 → CH3OC6H4NO + HBF4 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 (nitric acid) and the latter from a weak acid (nitrous acid).

As a source of nitrosyl complexes

Main article: Metal nitrosyl complex

NOBF4 reacts with some metal carbonyl complexes to yield related metal nitrosyl complexes. 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

References

References

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5. Williams, D. L. H.. (1988). "Nitrosation". [[Cambridge University Press.
6. (1994). "Direct Nitrosation of Aromatic Hydrocarbons and Ethers with the Electrophilic Nitrosonium Cation". Journal of Organic Chemistry.
7. T. W. Hayton, P. Legzdins, W. B. Sharp. "Coordination and Organometallic Chemistry of Metal-NO Complexes". Chemical Reviews 2002, volume 102, pp. 935–991.