Cyanate

The cyanate ion is an anion with the chemical formula written as [OCN]⁻ or [NCO]⁻. In aqueous solution it acts as a base, forming isocyanic acid, HNCO. 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. Organic cyanates are called isocyanates when there is a C-NCO bond and cyanates when there is a C-OCN bond.

Cyanate ion

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

with a single C-O bond and a triple C-N bond. 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 or the other, or both can be donated to Lewis acid acceptors. It can be described as an ambidentate ligand.