Ferricyanide

Ferricyanide
IUPAC name iron(3+) hexacyanide
Systematic name hexacyanidoferrate(III)
Other names ferric hexacyanide; hexacyanidoferrate(3-); hexacyanoferrate(III)
Identifiers
PubChem	439210
Jmol-3D images	Image 1
SMILES [C-]#N.[C-]#N.[C-]#N.[C-]#N.[C-]#N.[C-]#N.[Fe+3]
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Ferricyanide is the anion [Fe(CN)₆]³⁻.  It is also called hexacyanoferrate(III) and in rare, but systematic nomenclature, hexacyanidoferrate(III). The most common salt of this anion is potassium ferricyanide, a red crystalline material that is used as an oxidant in organic chemistry.

Properties

[Fe(CN)₆]³⁻ consists of a Fe³⁺ center bound in octahedral geometry to six cyanide ligands. The complex has O_h symmetry. The iron is low spin and easily reduced to the related ferrocyanide ion [Fe(CN)₆]⁴⁻, which is a ferrous (Fe²⁺) derivative. This redox couple is reversible and entails no making or breaking of Fe-C bonds:

[Fe(CN)₆]³⁻ + e⁻ → [Fe(CN)₆]⁴⁻

This redox couple is a standard in electrochemistry.

Compared to normal cyanides like potassium cyanide, ferricyanides are much less toxic because of the tight hold of the CN^- to the Fe³⁺. They do react with mineral acids, however, to release highly toxic hydrogen cyanide gas.

Uses

Treatment of ferricyanide with ferrous salts affords the brilliant, long-lasting pigment Prussian blue, the traditional color of blueprints.

See also

• Potassium ferricyanide
• Ferrocyanide