Ferricyanide
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Ferricyanide is the name for the anion [Fe(CN)6]3−. Its systematic name is hexacyanoferrate(III) ion. The most common salt of this anion is potassium ferricyanide, a red crystalline material that is used as an oxidant in organic chemistry.
[Fe(CN)6]3− consists of an Fe3+ center bound in octahedral geometry to six cyanide ligands. The complex has Oh 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 couple is a standard in electrochemistry.
Treatment of ferricyanide with ferrous salts affords the brilliant, long-lasting pigment Prussian Blue, the color of blueprints.