Dicobalt edetate is the coordination compound with the approximate formula Co₂(EDTA

EDTA

Ethylenediaminetetraacetic acid, widely abbreviated as EDTA , is a polyamino carboxylic acid and a colourless, water-soluble solid. Its conjugate base is named ethylenediaminetetraacetate. It is widely used to dissolve limescale. Its usefulness arises because of its role as a hexadentate ligand...

)(H₂O)₆.

Solutions of this solid have been used in Europe as an antidote to cyanide poisoning

Cyanide poisoning

Cyanide poisoning occurs when a living organism is exposed to a compound that produces cyanide ions when dissolved in water. Common poisonous cyanide compounds include hydrogen cyanide gas and the crystalline solids potassium cyanide and sodium cyanide...

.

It is a derivative of the (non-natural) amino acid ethylenediaminetetraacetate.

Structure

The compound is polymeric in the crystalline form. Half of the Co²⁺ ions are bound to the EDTA²⁻ and the other Co²⁺ ions are bound to four water ligands as well as carboxylate ligand

Ligand

In coordination chemistry, a ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. The bonding between metal and ligand generally involves formal donation of one or more of the ligand's electron pairs. The nature of metal-ligand bonding can range from...

s on the [Co(EDTA)]²⁻ entity. In aqueous solution, depolymerization occurs to give [Co(EDTA)]²⁻ and [Co(H₂O)₆]²⁺ ions, each of which is kinetically labile and has a high affinity for cyanide. Oxidants would convert the [Co(EDTA)]²⁻ into [Co(EDTA)]⁻, which would be unreactive toward cyanide because this complex would be "inert."