Sulfur dicyanide

Sidiropulos, Ph.D. thesis. University Frankfurt am Main, West Germany, 1978. 

Shriver, The Manipulation of Air-Sensitive Compounds, McGraw-Hill, New York, 1969. 

Submitted by RAMESH C. KUMAR and JEAN NE M. SHREEVE Checked by JERRY FOROPOULOS, jR.t 

Sulfur dicyanide, S(CN)2, was first synthesized in 1919. It has since been studied vigorously. It is usually prepared by the reaction of silver cyanide dispersed in warm carbon disulfide with sulfur dichloride. However, the yield of S(CN)2 when this method is employed has not been reported. The compound is useful as a precursor to thiols. 

The following procedure is a convenient and relatively inexpensive route to sulfur dicyanide by the reaction of sulfur dichloride and trimethylsilyl cyanide. No solvent is required, and thus recovery of S(CN)2 in high yield is very straightforward.  

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NjPtSioHg, Platinate(II), bis(pentasuIfido)-, bis(tetrapropylammonium), 21 13 NzPtSijHg, Platinate(IV), tris(penta-sulfido)-, diammonium, 21 12, 13 N2SCH4, Urea, thio-chromium(O) complexes, 23 2 N2SC2, Sulfur dicyanide, 24 125 N2SC4H6, 2H-Imidazole-2-thione, 1,3-di-hydro-1-methyl-cobalt complexes, 23 171 N2SCSH12, Thiourea, N,N,N methyl-... 

The reactor is warmed to 0° while the mixture is stirred. Warming should continue so that over a 1-hr period the reaction mixture reaches 25°. The vessel is then cooled to -23° (50/50 ethanol water, v/v, and liquid N2), and all substances that are volatile at this temperature should be transferred out under dynamic vacuum into a U-trap that can be removed subsequently to the fume hood. The contents of the U-trap are destroyed by hydrolysis in aqueous base. An off-white crystalline solid, S(CN)2, remains in the reaction vessel. The pure white crystalline sulfur dicyanide is obtained by subliming under vacuum (1-5 X 10 torr) (0.42 g, 80-85% yield). Sulfur dicyanide is stored in a glass vessel equipped with a Teflon stopcock at 0-10°. 

Sulfur dicyanide is a white crystalline solid that sublimes under vacuum at 25°. It is hygroscopic but can be stored under anhydrous conditions at 0° for long periods. It is not maricedly stable at 25°. On standing at this temperature in the absence of air, it slowly forms a yellow material of unknown composition. It is moderately soluble in water, very soluble in ether, and soluble in warm carbon disulfide. The Raman spectrum of S(CN)2 suggests a bent structure. The IR spectrum of the compound in a Nujol mull has absorption bands at 2190 (m) (C=N) and 1090 (w) (S—C) cm . ... 

A careful study of the molecular structure by microwave methods provides numerous interesting structural features. For example, it is apparent from Table III that the CF bond in FCN is shorter than in FCP. Many observations of this nature have been made and often correlated with simple bonding theory. A different effect may be illustrated by the —C"N chain in methylene cyanide, CH2(CN)2, and sulfur dicyanide, S(CN)2, which is not linear, but rather is bent slightly by about 3° and 5°, respectively. Such effects are not confined to the presence of a cyano group. Similar... 

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