Cyanate

The cyanate ion is an anion with the chemical formula . It is a resonance of three forms: (61%) ↔ (30%) ↔ (4%). Cyanate is the derived anion of isocyanic acid, H−N=C=O, and its lesser tautomer cyanic acid (a.k.a. cyanol), H−O−C≡N. Any salt containing the ion, such as ammonium cyanate, is called a cyanate. The cyanate ion is an isomer of the much-less-stable fulminate anion, or . The cyanate ion is an ambidentate ligand, forming complexes with a metal ion in which either the nitrogen or oxygen atom may be the electron-pair donor. It can also act as a bridging ligand. Compounds that contain the cyanate functional group, −O−C≡N, are known as cyanates or cyanate esters. The cyanate functional group is distinct from the isocyanate functional group, −N=C=O; the fulminate functional group, ; and the nitrile oxide functional group, or . The three atoms in a cyanate ion lie on a straight line, giving the ion a linear structure. The electronic structure is described most simply as Ö̤−C≡N: with a single C−O bond and a triple C≡N bond. (Or more completely as :Ö̤−C≡N: ↔ Ö̤=C=N̤̈ ↔ :O≡C−N̤̈:) The infrared spectrum of a cyanate salt has a band at ca. 2096 cm−1; such a high frequency is characteristic of a triple bond. The cyanate ion is a Lewis base. Both the oxygen and nitrogen atoms carry a lone pair of electrons and either one, the other, or both can be donated to Lewis acid acceptors. It can be described as an ambidentate ligand. Sodium cyanate is isostructural with sodium fulminate, confirming the linear structure of the cyanate ion. It is made industrially by heating a mixture of sodium carbonate and urea. A similar reaction is used to make potassium cyanate. Cyanates are produced when cyanides are oxidized. Use of this fact is made in cyanide decontamination processes where oxidants such as permanganate and hydrogen peroxide are used to convert toxic cyanide into less-toxic cyanate. Cyanate is an ambidentate ligand which can donate the pair of electrons on the nitrogen atom or the oxygen atom, or both.