Nitrosonium tetrafluoroborate

Nitrosonium tetrafluoroborate, also called nitrosyl tetrafluoroborate, is a chemical compound with the chemical formula NOBF₄. This colourless solid is used in organic synthesis as a nitrosating agent, diazotizing agent and a mild oxidant.

NOBF₄ is the nitrosonium salt of fluoroboric acid, and is composed of a nitrosonium cation, [NO]⁺, and a tetrafluoroborate anion, [BF₄]^−.

Reactions

The dominant property of NOBF₄ is the oxidizing power and electrophilic character of the nitrosonium cation. It forms colored charge transfer complexes with hexamethylbenzene and with 18-crown-6. The latter, a deep yellow species, provides a means to dissolve NOBF₄ in dichloromethane.

Nitrosonium tetrafluoroborate may be used to prepare metal salts of the type [M^II(CH₃CN)_x][BF₄]₂ (M = Cr, Mn, Fe, Co, Ni, Cu). The nitrosonium cation acts as the oxidizer, itself being reduced to nitric oxide gas:

With ferrocene the ferrocenium tetrafluoroborate is formed.

In its infrared spectrum of this salt, ν_NO shows a strong peak at 2387 cm^{−1}.

References