Nitrosonium

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+1 Key: KEJOCWOXCDWNID-UHFFFAOYSA-N;
	SMILES N#[O+];
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 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).^[2]

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⁻¹.^[3]

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.

Reaction of nitrosonium with aniline to form a diazonium salt

As an oxidizing agent

NO⁺, e.g. as NOBF₄, is a strong oxidizing agent:^[4]

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.^[5]

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.^[6] 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.^[7] 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

^ Nomenclature of Inorganic Chemistry : IUPAC Recommendations 2005 (Red Book). Cambridge: The Royal Society of Chemistry. 2005. p. 315. ISBN 978-0-85404-438-2.
^ 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.
^ 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.
^ 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.
^ Williams, D. L. H. (1988). Nitrosation. Cambridge, UK: Cambridge University. pp. 21–22. ISBN 0-521-26796-X.
^ 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.
^ T. W. Hayton, P. Legzdins, W. B. Sharp. "Coordination and Organometallic Chemistry of Metal-NO Complexes". Chemical Reviews 2002, volume 102, pp. 935–991.

[iupac2005-1] 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.

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