View source for Nitrosonium

{{Short description|Diatomic cation}}
{{Chembox
| Watchedfields = changed
| ImageFileL1 = Nitrosonium-2D-dimensions.svg
| ImageFileR1 = Nitrosonium-3D-balls.png
| ImageName = The structure of the nitrosonium ion
|IUPACName=Nitrilooxonium
| PIN = <!-- No PIN available in current IUPAC recommendations for inorganic chemistry (2005). -->
| SystematicName = Oxidonitrogen(1+)<ref name=iupac2005>{{cite book | title =  Nomenclature of Inorganic Chemistry : IUPAC Recommendations 2005 (Red Book) | url =  https://archive.org/details/nomenclatureinor2005conn | url-access =  limited | publisher = [[Royal Society of Chemistry|The Royal Society of Chemistry]] | date = 2005 | location = Cambridge | page = [https://archive.org/details/nomenclatureinor2005conn/page/n326 315]| isbn = 978-0-85404-438-2}}</ref>
| OtherNames = Nitrosonium<br />Iminooxidanium
| Section1 = {{Chembox Identifiers
| Abbreviations = NO(+)
| CASNo = 14452-93-8
| PubChem = 84878
| ChemSpiderID = 76569
| ChEBI = 29120
| SMILES = N#[O+]
| InChI = 1S/NO/c1-2/q+1
| InChIKey = KEJOCWOXCDWNID-UHFFFAOYSA-N
| Gmelin = 456}}
}}

The '''nitrosonium''' [[ion]] is {{chem2|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: {{chem2|NOClO4}}, {{chem2|NOSO4H}} ([[nitrosylsulfuric acid]], more descriptively written {{chem2|ONSO3OH}}) and {{chem2|NOBF4}}. The [[perchlorate|{{chem2|ClO4(−)}}]] and [[tetrafluoroborate|{{chem2|BF4(−)}}]] salts are slightly soluble in [[acetonitrile]] {{chem2|CH3CN}}. [[Nitrosonium tetrafluoroborate|NOBF<sub>4</sub>]] can be purified by sublimation at 200–250&nbsp;°C and {{convert|0.01|mmHg|Pa|abbr=on}}.<ref>{{cite journal |last1=Olah |first1=George A. |last2=Surya Prakash |first2=G. K. |last3=Wang |first3=Qi |last4=Li |first4=Xing-ya |last5=Surya Prakash |first5=G. K. |last6=Hu |first6=Jinbo |title=Nitrosonium Tetrafluoroborate |journal=Encyclopedia of Reagents for Organic Synthesis |date=15 October 2004 |pages=rn058.pub2 |doi=10.1002/047084289X.rn058.pub2|isbn=0471936235 }}</ref>

==Synthesis and spectroscopy==
{{chem2|NO+}} is [[isoelectronic]] with [[carbon monoxide|CO]], [[cyanide|{{chem2|CN−}}]] and [[dinitrogen|{{chem2|N2}}]]. It arises via protonation of [[nitrous acid]]:
:HONO + H<sup>+</sup> {{eqm}} NO<sup>+</sup> + H<sub>2</sub>O

In its [[infrared spectrum]] of its salts, ν<sub>NO</sub> is a strong peak in the range 2150-2400 cm<sup>−1</sup>.<ref>{{cite journal |doi=10.1039/JR9630003557 |title=670. The Infrared Spectrum of the Nitrosonium Ion |date=1963 |last1=Sharp |first1=D. W. A. |last2=Thorley |first2=J. |journal=Journal of the Chemical Society (Resumed) |page=3557 }}</ref>

==Chemical properties==
{{See also|Nitrosation}}

===Hydrolysis===
{{chem2|NO+}} reacts readily with water to form [[nitrous acid]]:
:{{chem2|NO(+) + H2O → HONO + H(+)}}
For this reason, nitrosonium compounds must be protected from water or even moist air. With base, the reaction generates nitrite:
:{{chem2|NO(+) + 2 NaOH → NaNO2 + Na(+) + H2O}}

===As a diazotizing agent===
{{chem2|NO+}} reacts with aryl amines, {{chem2|ArNH2}}, to give [[diazonium salt]]s, {{chem2|ArN2(+)}}. The resulting diazonium group is easily displaced (unlike the amino group) by a variety of nucleophiles.

[[File:Nitrosonium ion with amine reaction.png|thumb|400px|Reaction of nitrosonium with [[aniline]] to form a diazonium salt]]

===As an oxidizing agent===
{{chem2|NO+}}, e.g. as {{chem2|NOBF4}}, is a strong [[oxidizing agent]]:<ref>{{cite journal | author = N. G. Connelly, W. E. Geiger | title = Chemical Redox Agents for Organometallic Chemistry | journal = [[Chem. Rev.]] | year = 1996 | volume = 96 | pages = 877–910 | doi = 10.1021/cr940053x | pmid=11848774 | issue = 2}}</ref>
* vs. [[Ferrocene|ferrocene]]/ferrocenium, {{chem2|[NO]+}} in {{chem2|CH2Cl2}} solution has a redox potential of 1.00 V (or 1.46–1.48 V vs [[Saturated calomel electrode|SCE]]),
* vs. ferrocene/ferrocenium, {{chem2|[NO]+}} in {{chem2|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 [[ether]]s and [[oxime]]s, and couples di[[arylamine]]s<!-- (diaryl-amine)s -->.<ref>{{cite book|title=Nitrosation|first=D.&nbsp;L.&nbsp;H.|last=Williams|publisher=[[Cambridge University Press|Cambridge University]]|location=Cambridge, UK|year=1988|isbn=0-521-26796-X|url=https://archive.org/details/nitrosation0000will|url-access=registration|pages=21–22}}</ref>  

{{chem2|NOBF4}} is a convenient oxidant because the byproduct NO is a gas, which can be swept from the reaction using a stream of {{chem2|N2}}. Upon contact with air, NO forms {{chem2|NO2}}, which can cause secondary reactions if it is not removed. {{chem2|NO2}} is readily detectable by its characteristic orange color.

===Nitrosylation of arenes===
Electron-rich arenes are nitrosylated using NOBF<sub>4</sub>.<ref>{{cite journal|first1=E.|last1=Bosch|first2=J. K.|last2=Kochi|title=Direct Nitrosation of Aromatic Hydrocarbons and Ethers with the Electrophilic Nitrosonium Cation|journal=Journal of Organic Chemistry|year=1994|volume=59|issue=19 |pages=5573–5586|doi=10.1021/jo00098a015}}</ref> One example involves [[anisole]]:
: CH<sub>3</sub>OC<sub>6</sub>H<sub>5</sub> + NOBF<sub>4</sub> → CH<sub>3</sub>OC<sub>6</sub>H<sub>4</sub>NO + HBF<sub>4</sub>
Nitrosonium, {{chem2|NO+}}, is sometimes confused with nitronium, NO{{su|b=2|p=+}}, 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|Metal nitrosyl complex}}
NOBF<sub>4</sub> reacts with some metal carbonyl complexes to yield related metal nitrosyl complexes.<ref>T. W. Hayton, P. Legzdins, W. B. Sharp. "Coordination and Organometallic Chemistry of Metal-NO Complexes". Chemical Reviews 2002, volume 102, pp.&nbsp;935–991.</ref> In some cases, [NO]<sup>+</sup> does not bind the metal nucleophile but acts as an oxidant.
: (C<sub>6</sub>Et<sub>6</sub>)Cr(CO)<sub>3</sub> + NOBF<sub>4</sub> → [(C<sub>6</sub>Et<sub>6</sub>)Cr(CO)<sub>2</sub>(NO)]BF<sub>4</sub> + CO

==See also==
*[[Nitronium]] (NO<sub>2</sub><sup>+</sup>)
*[[Nitric oxide]] (NO)

==References==
{{Reflist}}

{{Nitric oxide signaling}}
{{Nitrogen compounds}}

[[Category:Oxycations]]
[[Category:Nitrogen(III) compounds]]