Prussian blue, a blue pigment used for paints and fabrics was the first synthetic coordination compound. It has a cubic structure with Fe in both +2 and +3 oxidation states. It is obtained by the addition of iron(III) salts to sodium/potassium ferrocyanide in aqueous solution. The action of sodium ferrocyanide with sodium nitrite in aqueous solution produces a beautiful ruby red diamagnetic iron complex (X), which gi