The cyanonickelates are a class of chemical compound containing anions consisting of

nickel Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow ...

atoms, and

cyanide Cyanide is a naturally occurring, rapidly acting, toxic chemical that can exist in many different forms. In chemistry, a cyanide () is a chemical compound that contains a functional group. This group, known as the cyano group, consists of ...

groups. The most important of these are the tetracyanonickelates containing four cyanide groups per nickel. The tetracyanonickelates contain the i(CN)₄sup>2− anion. This can exist in solution or in solid salts. The ion has cyanide groups arranged in a square around the central nickel ion. The symmetry of the ion is D_4''h''. The distance from the nickel atom to the carbon is 1.87 Å, and the carbon-nitrogen distance is 1.16 Å. Tetracyanonickelate(II) can be oxidised electrochemically in solution to yield tetracyanonickelate(III) i(CN)₄sup>−. i(CN)₄sup>− is unstable and Ni(III) oxidises the cyanide to

cyanate Cyanate is an anion with the structural formula , usually written . It also refers to any salt containing it, such as ammonium cyanate. It is an isomer of the much less stable fulminate anion .William R. Martin and David W. Ball (2019): "Sm ...

OCN⁻. Tetracyanonickelate(III) can add two more cyanide groups to form hexacyanonickelate(III). In combination with alkyldiamines, and other metal ions, tetracyanonickelate ions can form cage structure that can accommodate organic molecules. This is a Hofmann-diam-type clathrate. If the cation is a very strong reducing agent, such as Yb²⁺, i(CN)₄sup>2− can be reduced to i₂(CN)₆sup>4− where nickel atom is in the +1 oxidation state.

References

{{cyanides Nickel complexes Cyanometallates