Ferricyanide is the name of the anion . 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.
consists of a center bound in octahedral geometry to six cyanide ligands. The complex has O<sub>h</sub> symmetry. The iron is low-spin and easily reduced to the related ferrocyanide ion , which is a ferrous () derivative. This redox couple is reversible and entails no making or breaking of FeâÂÂC bonds:
This redox couple is a standard in electrochemistry.
Compared to main group cyanides like potassium cyanide, ferricyanides are much less toxic because of the strong bond between the cyanide ion () and the . They do react with mineral acids, however, to release highly toxic hydrogen cyanide gas.
Treatment of ferricyanide with iron(II) salts affords the brilliant, long-lasting pigment Prussian blue, the traditional color of blueprints.