Selenocyanate

A selenocyanate is an ion or chemical compound that contains the -SeCN group, which could be in the form of an anion, SeCN−. Organic selenocyanates also exist.

Some complex ions with transition metals such as silver and mercury (mercuriselenocyanates) are known. Mercuriselenocyanate salts also include K, Fe, Co, Ni, Cu, Zn, and Cd. Complex ions include Fe(NCSe)63−, Fe(NCSe)64−, Fe(NCSe)42−, Co(NCSe)64−, Co(NCSe)42−, Ni(NCSe)64−, Zn(NCSe)64−, Rh(NCSe)64−, Pd(NCSe)42−, Ag(SeCN)2−, Cd(NCSe)42−, Cd(NCSe)64−, Dy(NCSe)63−, Ho(NCSe)63−, Er(NCSe)63−, Pt(NCSe)62−, Au(NCSe)4−, and Hg(NCSe)42−.

For hard metals, the negative charge is on the nitrogen atom which coordinates with the metal atom. Examples include Ti(NCSe)62−, V(NCSe)63−, VO(NCSe)42−, Cr(NCSe)63−, Mn(NCSe)42−, Mn(NCSe)42−, Y(NCSe)63−, Zr(NCSe)62−, Mo(NCSe)63−, Pr(NCSe)63−, Nd(NCSe)63−, Sm(NCSe)63−, Hf(NCSe)62−, Re2(NCSe)82−, Pa(NCSe)84− and U(NCSe)84−.

Production
Selenocyanate can be produced in the reaction of selenium, selenide, selenite or selenate with cyanide ions.
 * Se2− + CN− + 0.5 O2 → SeCN− + 2OH−
 * SeO32− + 3CN− → 2OCN− + SeCN− + 2OH−
 * SeO42− + 4CN− → 3OCN− + SeCN− + 2OH−

Reactions
Selenocyanate is oxidised to selenium and cyanate by bis (trifluoroacetoxy) iodobenzene.

Application
Selenocyanate is component of pollution from oil refineries and mine drainage water. Remediation methods have been investigated to extract selenocyanate from water. Methods considered include precipitation by metal salts, or extraction by plants. Indian mustard converts some selenocyanate to selenocystine and selenomethionine, and volatiles dimethylselenide and methylselenocyanate.