Benzenediazonium tetrafluoroborate is an organic compound with the

formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwee ...

₆H₅N₂F₄. It is a salt of a

diazonium cation Diazonium compounds or diazonium salts are a group of organic compounds sharing a common functional group where R can be any organic group, such as an alkyl or an aryl, and X is an inorganic or organic anion, such as a halide. General properti ...

and tetrafluoroborate. It exists as a colourless solid that is soluble in polar solvents. It is the parent member of the aryl

diazonium compound Diazonium compounds or diazonium salts are a group of organic compounds sharing a common functional group where R can be any organic group, such as an alkyl or an aryl, and X is an inorganic or organic anion, such as a halide. General propert ...

s, which are widely used in organic chemistry.

Synthesis

Diazotization of aniline in the presence of hydrochloric acid: : C₆H₅NH₂ + HNO₂ + HCl → ₆H₅N₂l + 2 H₂O The tetrafluoroborate can be obtained from crude benzenediazonium chloride by salt metathesis using tetrafluoroboric acid. : ₆H₅N₂l + HBF₄ → ₆H₅N₂F₄ + HCl The tetrafluoroborate is more stable than the chloride.

Properties

The diazo group (N₂) can be replaced by many other groups, usually anions, giving a variety of substituted phenyl derivatives: :C₆H₅N₂⁺ + Nu⁻ → C₆H₅Nu + N₂ These transformations are associated with many named reactions including the Schiemann reaction, Sandmeyer reaction, and Gomberg-Bachmann reaction. A wide range of groups that can be used to replace N₂ including halide, SH⁻, CO₂H⁻, OH⁻. Of considerable practical value in the dye industry are the diazo coupling reactions. The reaction of phenyldiazonium salts with aniline gives 1,3-diphenyltriazene. The structure of the salt has been verified by X-ray crystallography. The N-N bond distance is 1.083(3) Å.

Safety

Whereas the chloride salt is explosive, the tetrafluoroborate is readily isolated.

References

{{Reflist Benzene derivatives Diazo compounds Tetrafluoroborates Phenyl compounds