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

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 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