hexacyanometallate

Hexacyanometallate refers to coordination compounds containing the hexacyanometallate anion, which has the general formula [M(CN)₆]ⁿ⁻. In this formula, M represents a metal atom and CN represents the cyanide ligand. The charge, n-, depends on the oxidation state of the metal. These anions are characterized by a central metal ion octahedrally coordinated by six cyanide ligands. The cyanide ligands bridge to the metal ion through their carbon atoms.

Hexacyanometallate anions are known for their stability due to the strong field nature of the cyanide ligand and the formation of coordinate covalent bonds. They are often soluble in water, forming salts with various cations. Common counterions include alkali metals like sodium and potassium, leading to compounds such as potassium hexacyanoferrate(II) (K₄[Fe(CN)₆]), also known as yellow prussiate of potash, and potassium hexacyanoferrate(III) (K₃[Fe(CN)₆]), known as red prussiate of potash.

These compounds find applications in various fields. For instance, hexacyanoferrates are used as pigments (e.g., Prussian blue), in electrochemistry, and as analytical reagents. Some hexacyanometallates can exhibit interesting magnetic and optical properties, making them subjects of research in materials science. It is important to note that while these compounds contain the cyanide group, the cyanide is tightly bound to the metal and does not readily dissociate to release free cyanide ions, making them generally less toxic than simple cyanide salts. However, under specific harsh conditions, such as strong acidic hydrolysis, toxic hydrogen cyanide gas can be liberated.