Cyanogen Monoselenide, Se(CN)₂

Cyanogen Monoselenide or Selenium Dicyanide, Se(CN)₂, may be obtained by the action of silver selenocyanide, AgCNSe, on cyanogen iodide. Linnemann obtained it by the decomposition of silver cyanide with selenium bromide in carbon disulphide solution. Cyanogen triselenide heated to 108° C. in a vacuum also yields the monoselenide.

It consists of small tabular crystals which readily sublime. It is only slightly soluble in water, alcohol and ether; in chloroform and in carbon disulphide it is more soluble. It is decomposed by cold water into the triselenide, ammonium selenocyanate and selenious and hydrocyanic acids. Hot water decomposes it into selenious and hydrocyanic acids.