Cobalt(II) cyanide is the

inorganic compound An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds⁠that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistry''. Inorgan ...

with the empirical formula Co(CN)₂ and structural formula Co₃ o(CN)₅sub>2. It is a

coordination polymer Coordination may refer to: * Coordination (linguistics), a compound grammatical construction * Coordination complex, consisting of a central atom or ion and a surrounding array of bound molecules or ions ** A chemical reaction to form a coordinat ...

that has attracted intermittent attention over many years in the areas of inorganic synthesis and

homogeneous catalysis In chemistry, homogeneous catalysis is catalysis where the catalyst is in same phase as reactants, principally by a soluble catalyst in a solution. In contrast, heterogeneous catalysis describes processes where the catalysts and substrate are in d ...

. The anhydrous and octahydrate forms are both blue solids insoluble in water.

Preparation and structure

The octahydrate is prepared by the reaction between

tetraethylammonium Tetraethylammonium (TEA) is a quaternary ammonium cation with the chemical formula , consisting of four ethyl groups (, denoted Et) attached to a central nitrogen atom. It is a counterion used in the research laboratory to prepare lipophilic salt ...

pentacyanocobaltate In chemistry, pentacyanocobaltate is the coordination complex with the formula . When crystallized with a quaternary ammonium cation, it can be obtained as a yellow solid. Pentacyanocobaltate attracted attention as an early example of a metal com ...

and

cobalt(II) chloride Cobalt(II) chloride is an inorganic compound, a salt of cobalt and chlorine, with the formula . The compound forms several hydrates ·''n'', for ''n'' = 1, 2, 6, and 9. Claims of the formation of tri- and tetrahydrates have not been confirmed.M. ...

: : Heating of the octahydrate at 100 °C produces the anhydrous form. The anhydrous form can also be prepared from the reaction of cobalt(II) bromide and

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 ...

sodium cyanide Sodium cyanide is a compound with the formula Na C N and the structure . It is a white, water-soluble solid. Cyanide has a high affinity for metals, which leads to the high toxicity of this salt. Its main application, in gold mining, also expl ...

liquid ammonia Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the formula . A stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pungent smell. It is widely used in fertilizers, ...

, then heating the resulting ammoniate to 210 °C in

ethyl benzoate Ethyl benzoate, C9H10O2, is an ester formed by the condensation of benzoic acid and ethanol. It is a colorless liquid that is almost insoluble in water, but miscible with most organic solvents. As with many volatile esters, ethyl benzoate has a ...

. The structural formula Co₃ o(CN)₅sub>2 shows that cobalt(II) cyanide consists of Co²⁺ and o(CN)₅sup>3– (

) ions, the latter of which also has cobalt in its +2

oxidation state In chemistry, the oxidation state, or oxidation number, is the hypothetical Electrical charge, charge of an atom if all of its Chemical bond, bonds to other atoms are fully Ionic bond, ionic. It describes the degree of oxidation (loss of electrons ...

Oxygenation and redox

A red trihydrated has also been reported, but this was later shown to be the oxygenated derivative containing the ion o(CN)₅(O₂)sup>3–. The oxygenated derivative is obtained as a reddish-brown precipitate by adding two equivalents of

to a solution of cobalt(II) salts in air. With excess cyanide, the red-brown solid dissolves to give

, which oxidizes in the presence of oxygen to hexacyanocobaltate(III).

Uses

Cobalt(II) cyanide has been used as a precursor to

dicobalt octacarbonyl Dicobalt octacarbonyl is an organocobalt compound with composition . This metal carbonyl is used as a reagent and catalyst in organometallic chemistry and organic synthesis, and is central to much known organocobalt chemistry. It is the parent ...

References

Cobalt(II) compounds Cyanides {{inorganic-compound-stub