Ferricyanide is the name of the
anion
An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...
CN)
6">cyanide.html" ;"title="e(cyanide">CN)
6sup>3−. It is also called hexacyanoferrate(III) and in rare, but systematic name">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
e(CN)6sup>3− consists of a Fe
3+ center bound in
octahedral geometry to six
cyanide
In chemistry, cyanide () is an inorganic chemical compound that contains a functional group. This group, known as the cyano group, consists of a carbon atom triple-bonded to a nitrogen atom.
Ionic cyanides contain the cyanide anion . This a ...
ligand
In coordination chemistry, a ligand is an ion or molecule with a functional group that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's el ...
s. The complex has O
h symmetry
Symmetry () in everyday life refers to a sense of harmonious and beautiful proportion and balance. In mathematics, the term has a more precise definition and is usually used to refer to an object that is Invariant (mathematics), invariant und ...
. The iron is
low spin and easily reduced to the related
ferrocyanide
Ferrocyanide is the anion cyanide.html" ;"title="e(cyanide">CN)6sup>4−. Salts of this coordination complex give yellow solutions. It is usually available as the salt potassium ferrocyanide, which has the formula K4Fe(CN)6. e(CN)6sup>4− is ...
ion
e(CN)6sup>4−, which is a ferrous (Fe
2+) derivative. This redox couple is reversible and entails no making or breaking of Fe–C bonds:
:
e(CN)6sup>3− + e
− ⇌
e(CN)6sup>4−
This
redox couple is a standard in
electrochemistry
Electrochemistry is the branch of physical chemistry concerned with the relationship between Electric potential, electrical potential difference and identifiable chemical change. These reactions involve Electron, electrons moving via an electronic ...
.
Compared to main group
cyanide
In chemistry, cyanide () is an inorganic chemical compound that contains a functional group. This group, known as the cyano group, consists of a carbon atom triple-bonded to a nitrogen atom.
Ionic cyanides contain the cyanide anion . This a ...
s like
potassium cyanide
Potassium cyanide is a compound with the formula KCN. It is a colorless salt, similar in appearance to sugar, that is highly soluble in water. Most KCN is used in gold mining, organic synthesis, and electroplating. Smaller applications include ...
, ferricyanides are much less toxic because of the strong bond between the cyanide ion (CN
−) and the Fe
3+. They do react with mineral acids, however, to release highly toxic
hydrogen cyanide
Hydrogen cyanide (formerly known as prussic acid) is a chemical compound with the chemical formula, formula HCN and structural formula . It is a highly toxic and flammable liquid that boiling, boils slightly above room temperature, at . HCN is ...
gas.
Uses
Treatment of ferricyanide with iron(II) salts affords the brilliant, long-lasting pigment
Prussian blue
Prussian blue (also known as Berlin blue, Brandenburg blue, Parisian and Paris blue) is a dark blue pigment produced by oxidation of ferrous ferrocyanide salts. It has the chemical formula . It consists of cations, where iron is in the oxidat ...
, the traditional color of
blueprints.
See also
*
Potassium ferricyanide
*
Ferrocyanide
Ferrocyanide is the anion cyanide.html" ;"title="e(cyanide">CN)6sup>4−. Salts of this coordination complex give yellow solutions. It is usually available as the salt potassium ferrocyanide, which has the formula K4Fe(CN)6. e(CN)6sup>4− is ...
References
{{Cyanides
Anions
Iron complexes
Cyanometallates
Iron(III) compounds