tetracyanonickelateII

Tetracyanonickelate(II) is an inorganic coordination complex with the chemical formula [Ni(CN)4]2-. It is an anion where a central nickel atom in the +2 oxidation state is coordinated to four cyanide ligands. The complex typically exists as a salt with accompanying cations, such as potassium or sodium, forming compounds like potassium tetracyanonickelate(II) (K2[Ni(CN)4]).

This complex is known for its planar square geometry around the nickel ion. Nickel(II) has a d8 electron configuration, and in the presence of strong field ligands like cyanide, it typically forms low-spin complexes. In the case of tetracyanonickelate(II), the d orbitals split, and the electrons occupy the lower energy levels, resulting in a diamagnetic compound.

Tetracyanonickelate(II) can be prepared through various synthetic routes, often involving the reaction of a soluble nickel(II) salt with an excess of a cyanide salt in aqueous solution. It is a relatively stable complex in solution, though it can decompose under strongly acidic conditions, releasing hydrogen cyanide. Its properties, such as solubility and reactivity, depend significantly on the nature of the counter-cation. It has found applications in analytical chemistry and as a precursor in the synthesis of other nickel complexes.