Sulfur dicyanide
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CompTox Dashboard (EPA) |
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| Properties | |
| 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)[1] |
| 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).
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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 Sx(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, 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