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Sulfur dicyanide
Identifiers
CAS Number	627-52-1;
3D model (JSmol)	Interactive image;
ChemSpider	120218;
PubChem CID	136447;
CompTox Dashboard (EPA)	DTXSID70211767 ;
	InChI InChI=1S/C2N2S/c3-1-5-2-4 Key: RFMQOHXWHFHOJF-UHFFFAOYSA-N;
	SMILES C(#N)SC#N;
Properties
Chemical formula	C2N2S
Molar mass	84.10 g·mol−1
Appearance	white solid
Density	1.48 g/cm3
Melting point	62.3 °C (144.1 °F; 335.4 K)
Sublimation; conditions	30–40 °C, 1 atm
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Sulfur dicyanide is an inorganic compound with the formula S(CN)₂. A white, slightly unstable solid, the compound is mainly of theoretical and fundamental interest given its simplicity.^[2]^: 8 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.^[3] According to X-ray crystallography, the molecule is planar, the SCN units are linear, with an S-C-S angle of 95.6°.^[4]

Sulfur dicyanide begins to sublime at 30-40 °C and melts at 60 °C.^[5] Under an inert atmosphere, it slowly decomposes to a yellow polymer at room temperature with a rate increasing in temperature.^[2]^: 8, 14 The compound is unstable in acid, disproportionating to thiocyanate, cyanate, hydrogen sulfate,and cyanide,^[1] and neutral moisture induces decomposition to thiocyanic and cyanic acids. Stable solutions are possible in many organic solvents.^[2]^: 14

Sulfur dicyanide was first synthesized by Lassaigne in 1828 from silver cyanide and sulfur dichloride.^[2]^: 8 Subsequent developments include Linneman's discovery that the same product arose from silver thiocyanate and cyanogen iodide,^[5] and Söderbäck's extensive analysis of reactions between metal cyanides and sulfur halides.^[6] Linneman also discovered that sulfur dicyanide reacts with ammonia à la Pinner to give an amidine without displacing the S–C linkage,^[5] although dimethylamine induces decomposition to dimethylcyanamide and dimethylammonium thiocyanate.^[2]^: 14

Sulfur dicyanide generally reacts with noble metals to give heteroleptic cyano-thiocyano complices, although in rare cases it can ligate without decomposition, e.g.:^[2]^: x

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

^ ^a ^b Wilson, I. R.; Harris, G. M. (January 1, 1961). "The oxidation of thiocyanate ion by hydrogen peroxide II: The acid-catalyzed reaction". Journal of the American Chemical Society. 83 (2). doi:10.1021/ja01463a007.
^ ^a ^b ^c ^d ^e ^f Hamilton, Diane Singleton (26 November 1974). Reactions of Sulfur-Dicyanide and Sulfur-Dichlorides with Transition Metal Complexes (PhD). Louisiana State University and Agricultural & Mechanical College.
^ Steudel, Ralf; Bergemann, Klaus; Kustos, Monika (1994). "Crystal and Molecular Structure of Dicyanotetrasulfane S₄(CN)₂". Zeitschrift für anorganische und allgemeine Chemie. 620: 117–120. doi:10.1002/zaac.19946200119.
^ Emerson, K. (1966). "The Crystal and Molecular Structure of Sulfur Dicyanide". Acta Crystallographica. 21 (6): 970–974. Bibcode:1966AcCry..21..970E. doi:10.1107/S0365110X66004262.
^ ^a ^b ^c Linneman, F. (1861). "Untersuchung über das Cyansulfid" [Research on cyanogen sulfide]. Liebigs Annalen der Chemie (in German). 120 (1): 36–47. doi:10.1002/jlac.18611200103 – via HathiTrust.
^ Söderbäck, Erik (1919). "Studien über das freie Rhodan". Justus Liebig's Annalen der Chemie. 419 (3): 217–322. doi:10.1002/jlac.19194190302.