Thenitrosoniumion isNO+, in which thenitrogen atom is bonded to anoxygen atom with abond order of 3, and the overall diatomic species bears a positive charge. It can be viewed asnitric oxide with one electron removed. This ion is usually obtained as the following salts:NOClO4,NOSO4H (nitrosylsulfuric acid, more descriptively writtenONSO3OH) andNOBF4. TheClO−4 andBF−4 salts are slightly soluble inacetonitrileCH3CN.NOBF4 can be purified by sublimation at 200–250 °C and 0.01 mmHg (1.3 Pa).[2]
NO+ reacts with aryl amines,ArNH2, to givediazonium salts,ArN+2. The resulting diazonium group is easily displaced (unlike the amino group) by a variety of nucleophiles.
Reaction of nitrosonium withaniline to form a diazonium salt
NOBF4 is a convenient oxidant because the byproduct NO is a gas, which can be swept from the reaction using a stream ofN2. Upon contact with air, NO formsNO2, which can cause secondary reactions if it is not removed.NO2 is readily detectable by its characteristic orange color.
Electron-rich arenes are nitrosylated using NOBF4.[6] One example involvesanisole:
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).
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
^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. pp. rn058.pub2.doi:10.1002/047084289X.rn058.pub2.ISBN0471936235.
^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.
^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.
