Sulfur dicyanide is an

inorganic compound An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds⁠that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistry''. Inorgan ...

with the formula S(CN)₂. A white, slightly unstable solid, the compound is mainly of theoretical and fundamental interest given its simplicity. It is the first member of the dicyanosulfanes S_x(CN)₂, which includes thiocyanogen ((SCN)₂) and higher polysulfanes up to S₄(CN)₂. According to

X-ray crystallography X-ray crystallography is the experimental science of determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to Diffraction, diffract in specific directions. By measuring th ...

, the molecule is planar, the SCN units are linear, with an S-C-S angle of 95.6°. Sulfur dicyanide begins to sublime at 30-40 °C and melts at 60 °C. Under an inert atmosphere, it slowly decomposes to a yellow

polymer A polymer () is a chemical substance, substance or material that consists of very large molecules, or macromolecules, that are constituted by many repeat unit, repeating subunits derived from one or more species of monomers. Due to their br ...

at room temperature with a rate increasing in temperature. The compound is unstable in

acid An acid is a molecule or ion capable of either donating a proton (i.e. Hydron, hydrogen cation, H+), known as a Brønsted–Lowry acid–base theory, Brønsted–Lowry acid, or forming a covalent bond with an electron pair, known as a Lewis ...

, disproportionating to

thiocyanate Thiocyanates are salts containing the thiocyanate anion (also known as rhodanide or rhodanate). is the conjugate base of thiocyanic acid. Common salts include the colourless salts potassium thiocyanate and sodium thiocyanate. Mercury(II) t ...

, cyanate,

sulfate The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many ...

,and

cyanide In chemistry, cyanide () is an inorganic chemical compound that contains a functional group. This group, known as the cyano group, consists of a carbon atom triple-bonded to a nitrogen atom. Ionic cyanides contain the cyanide anion . This a ...

, and neutral moisture induces decomposition to thiocyanic and cyanic acids. Stable solutions are possible in many organic solvents. Sulfur dicyanide was first synthesized by Lassaigne in 1828 from silver cyanide and

sulfur dichloride Sulfur dichloride is the chemical compound with the formula . This cherry-red liquid is the simplest sulfur chloride and one of the most common, and it is used as a precursor to organosulfur compounds. It is a highly corrosive and toxic substance ...

. Subsequent developments include Linneman's discovery that the same product arose from silver thiocyanate and cyanogen iodide, and Söderbäck's extensive analysis of reactions between metal cyanides and sulfur halides. Linneman also discovered that sulfur dicyanide reacts with

ammonia Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the chemical formula, formula . A Binary compounds of hydrogen, stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pu ...

à la Pinner to give an

amidine Amidines are organic compounds with the functional group RC(NR)NR2, where the R groups can be the same or different. They are the imine derivatives of amides (RC(O)NR2). The simplest amidine is formamidine, HC(=NH)NH2. Examples of amidines includ ...

without displacing the S–C linkage, although

dimethylamine Dimethylamine is an organic compound with the formula (CH3)2NH. This secondary amine is a colorless, flammable gas with an ammonia-like odor. Dimethylamine is commonly encountered commercially as a solution in water at concentrations up to around ...

induces decomposition to dimethylcyanamide and dimethylammonium thiocyanate. Sulfur dicyanide generally reacts with noble metals to give heteroleptic cyano-thiocyano complices, although in rare cases it can ligate without decomposition, e.g.: :Ir(CO)(PPh₃)₂Cl + NCSCN → Ir(CO)(CN)(SCN)(PPh₃)₂Cl :Ir(N₂)(PPh₃)₂Cl + S(CN)₂ → Ir(S(CN)₂)(PPh₃)₂Cl

References

{{cyanides Inorganic carbon compounds Inorganic sulfur compounds Inorganic nitrogen compounds Thiocyanates