Cyanogen polysulfides

The thiocyanate group has pseudohalogen properties, and the cyanogen polysulfides may alternatively be termed sulfur thiocyanates. The behavior of the tri- and tetrasulfides towards nucleophilic reagents 82) is consistent with the thiocyanate nomenclature. 

The presence of unbranched sulfur chains in the cyanogen polysulfides is evident from the Raman spectra recorded by Feh r and Weber 77). The characteristic S—S stretching and S—S—S bending frequencies occur, and the CsN frequency varies with increasing chain length in a way analogous to unbranched methylene a,cc-dinitriles. 

Structure determinations by X-ray and electron diffraction methods have demonstrated the presence of unbranched chains of up to six divalent sulfur atoms in inorganic polysulfides, four divalent ones in salts of polythionic acids, and three in disulfonyl, dialkyl, and cyanogen derivatives. The synthetic and Raman-spectroscopic work of Feh6r has established the presence of unbranched structures with up to five sulfur atoms in organic polysulfides, and eight in the cyanogen polysulfide, polysulfur dichloride, and hydrogen polysulfide series. The results are supported by extensive physicochemical evidence of less conclusive nature. 

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