FeCN63

FeCN63 typically denotes the hexacyanoferrate(III) ion, [Fe(CN)6]3−, commonly referred to as ferricyanide. It forms salts such as potassium ferricyanide K3[Fe(CN)6] and sodium ferricyanide Na3[Fe(CN)6]. The ferricyanide/ferrocyanide system is one of the best-studied, highly reversible redox couples in aqueous chemistry and electrochemistry.

Structure and properties: The complex features an Fe(III) center coordinated by six cyanide ligands in an octahedral arrangement, giving high-field, low-spin Fe(III). The cyanide ligands bind strongly through carbon, producing a very stable, largely inert complex with Oh symmetry. In solution, ferricyanide typically appears as an orange or yellowish solution, depending on concentration and counterions.

Preparation: Ferricyanide is commonly prepared by oxidizing ferrocyanide [Fe(CN)6]4−, for example from salts like K4[Fe(CN)6], using oxidants such as Fe3+ ions, chlorine, or molecular oxygen. It can also be generated electrochemically by applying an appropriate potential to ferrocyanide solutions.

Reactions and redox chemistry: The ferricyanide/ferrocyanide couple, [Fe(CN)6]3−/[Fe(CN)6]4−, is a one-electron, highly reversible redox system with a standard potential around +0.36 V versus the standard hydrogen electrode under standard conditions. Ferricyanide acts as a mild oxidant and is readily reduced to ferrocyanide in various chemical and biochemical contexts.

Applications: Ferricyanide is widely used as a redox mediator in analytical chemistry and biochemical assays, as a standard for electrochemical measurements, and as a mild oxidizing agent in certain synthetic and procedural contexts. Its stability, low toxicity relative to other cyanide complexes, and well-behaved electrochemistry contribute to its prominence.

Safety: While the cyanide ligands are tightly bound, ferricyanide salts should be handled with standard chemical precautions. Acidic conditions can release hydrogen cyanide if the complex is decomposed, so avoid strong acids and improper heating. Maintain appropriate ventilation and protective equipment.