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Nitrosonium

Names
IUPAC name Nitrilooxonium
Systematic IUPAC name Oxidonitrogen(1+)
Other names Nitrosonium Iminooxidanium
Identifiers
CAS Number	14452-93-8
3D model (JSmol)	Interactive image
Abbreviations	NO(+)
ChEBI	CHEBI:29120
ChemSpider	76569
Gmelin Reference	456
PubChem CID	84878
CompTox Dashboard (EPA)	DTXSID901027026 DTXSID90932326, DTXSID901027026
InChI InChI=1S/NO/c1-2/q+1Key: KEJOCWOXCDWNID-UHFFFAOYSA-N
SMILES N#
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). Infobox references

The nitrosonium ion is NO, 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: NOClO₄, NOSO₄H (nitrosylsulfuric acid, more descriptively written ONSO₃OH) and NOBF₄. The ClO−4 and BF−4 salts are slightly soluble in acetonitrile CH₃CN. NOBF₄ can be purified by sublimation at 200–250 °C and 0.01 mmHg (1.3 Pa).

Synthesis and spectroscopy

NO is isoelectronic with CO, CN and N₂. It arises via protonation of nitrous acid:

HONO + H ⇌ NO + H₂O

In its infrared spectrum of its salts, ν_NO is a strong peak in the range 2150-2400 cm.

Chemical properties

Hydrolysis

NO reacts readily with water to form nitrous acid:

NO + H₂O → HONO + H

For this reason, nitrosonium compounds must be protected from water or even moist air. With base, the reaction generates nitrite:

NO + 2 NaOH → NaNO₂ + Na + H₂O

As a diazotizing agent

NO reacts with aryl amines, ArNH₂, to give diazonium salts, ArN+2. The resulting diazonium group is easily displaced (unlike the amino group) by a variety of nucleophiles.

As an oxidizing agent

NO, e.g. as NOBF₄, is a strong oxidizing agent:

• vs. ferrocene/ferrocenium, [NO] in CH₂Cl₂ solution has a redox potential of 1.00 V (or 1.46–1.48 V vs SCE),
• vs. ferrocene/ferrocenium, [NO] in CH₃CN 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.

NOBF₄ is a convenient oxidant because the byproduct NO is a gas, which can be swept from the reaction using a stream of N₂. Upon contact with air, NO forms NO₂, which can cause secondary reactions if it is not removed. NO₂ 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, NO, is sometimes confused with nitronium, NO
₂, 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

NOBF₄ reacts with some metal carbonyl complexes to yield related metal nitrosyl complexes. In some cases, does not bind the metal nucleophile but acts as an oxidant.

(C₆Et₆)Cr(CO)₃ + NOBF₄ → BF₄ + CO

See also

• Nitronium (NO₂)
• Nitric oxide (NO)

References

1. Nomenclature of Inorganic Chemistry : IUPAC Recommendations 2005 (Red Book). Cambridge: The Royal Society of Chemistry. 2005. p. 315. ISBN 978-0-85404-438-2.
2. Olah, George A.; Surya Prakash, G. K.; Wang, Qi; Li, Xing-ya; Surya Prakash, G. K.; Hu, Jinbo (15 October 2004). "Nitrosonium Tetrafluoroborate". Encyclopedia of Reagents for Organic Synthesis: rn058.pub2. doi:10.1002/047084289X.rn058.pub2. ISBN 0471936235.
3. Sharp, D. W. A.; Thorley, J. (1963). "670. The Infrared Spectrum of the Nitrosonium Ion". Journal of the Chemical Society (Resumed): 3557. doi:10.1039/JR9630003557.
4. N. G. Connelly, W. E. Geiger (1996). "Chemical Redox Agents for Organometallic Chemistry". Chem. Rev. 96 (2): 877–910. doi:10.1021/cr940053x. PMID 11848774.
5. Williams, D. L. H. (1988). Nitrosation. Cambridge, UK: Cambridge University. pp. 21–22. ISBN 0-521-26796-X.
6. Bosch, E.; Kochi, J. K. (1994). "Direct Nitrosation of Aromatic Hydrocarbons and Ethers with the Electrophilic Nitrosonium Cation". Journal of Organic Chemistry. 59 (19): 5573–5586. doi:10.1021/jo00098a015.
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.

• Oxycations
• Nitrogen(III) compounds