Benzenediazonium tetrafluoroborate

Diazotization of aniline with nitrous acid in the presence of hydrochloric acid gives phenyldiazonium chloride: : C6H5NH2 + HNO2 + HCl → [C6H5N2]Cl + 2 H2O The required nitrous acid can be generated in situ by combining sodium nitrite and hydrochloric acid. The tetrafluoroborate salt of phenyl diazonium can be obtained from benzenediazonium chloride by salt metathesis using tetrafluoroboric acid. : [C6H5N2]Cl + HBF4 → [C6H5N2]BF4 + 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. Reaction 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==

While tetrafluoroborate salts are typically less sensitive than chlorides, all aryldiazonium salts should be assumed to pose a risk of explosion "unless proved otherwise". Benzenediazonium tetrafluoroborate has been described as shock-insensitive, and, when dry, decomposes smoothly upon heating. ==References==