Heptasulfur imide

Heptasulfur imide is formed by the reaction of di sulfur dichloride with ammonia, the chief by-products being 

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It decomposes explosively to its elements at 100°C. Previously prepared from the explosive tetranitride [1], it may now safely be prepared from the stable intermediate, heptasulfur imide [2]. 

Heptagold heteronuclear cluster compounds X-ray crystallography, 39 371-373 Heptasulfur imide, 2 161-164 Herbicide-binding protein, 33 224 Heteroallenes, cycloaddition to iminoboianes, 31 161... 

Heptasulfur imide, synthesis 25 Imidosulfuric acid chloride, synthesis 26 Dialkylsulfamoyl chlorides, synthesis 27 N- and JV,AT -Substituted sulfamides, synthesis 28 Dialkylamides of (trichlorophosphoranylidene)sulfamic acid, synthesis 29... 

There is an extensive chemistry of heptasulfur imide, from which many inorganic and organic derivatives have been made. The chemistry of the diimides and triimides is only just beginning to be studied, and promises to be even more interesting. 

Heptasulfur imide follows soon after the sulfur, with which it overlaps slightly. It is best to reject the early sulfur-contaminated fractions, which entails little loss. The pure fractions are combined, and on evaporation deposit large, nearly colorless rhombs of the imide. Yield 25-45 g. To remove any remaining traces of sulfur, the imide can be recrystallized by evaporation of a warm solution in carbon disulfide, or by allowing a satvurated solution in boiling carbon tetrachloride or hot toluene to cool. 

The 1, -hexasulfur diimide fraction comes off the column after the heptasulfur imide, and should be clearly separated both from it and from the other diimides which follow. Yield 8 g. 

For the triimides, it is expedient to increase the scale of the preparation, and then to effect a preliminary concentration of the triimides from the other imides so that the chromatography can be done on a much smaller column. The crude imide mixture is made as just described, but uang 3 1. of dimethylfonn-amide and 420 ml. (5.2 moles) of disulfur dichloride. After grinding finely once or twice as before, it is extracted with successive portions of dry, peroxide-free ethyl ether, totaling 3 1. The combined ether extracts are left to evaporate spontaneously until 150-300 ml. of cold liquid is left. Evaporation is continued until it is judged that more than half of the solute has crystallized. The solution is decanted away from the mass of crystals of heptasulfur imide and hexasulfur diimides, and allowed to evaporate to dryness, leaving 30-40 g. of solid, which consists... 

Heptasulfur imide is formed from elementary sulfur or from the product of the reaction of sulfur with sulfur trioxide by treatment with liquid ammonia at room temperature. A disproportionation reaction takes place in which, in addition to H2S and S4N4, S7NH is produced from the elementary sulfur or S203 (1, 39). 

Heptasulfur imide melts at 113.5° without decomposition, but the melting point is strongly depressed by small admixtures with sulfur. A eutectic between S7NH and Ss is observed at 91.5° with 46% of sulfur (15). Otherwise the physical behavior of S7NH strongly resembles that of elementary sulfur. Thus, for example, it is not wetted by water but dissolves in many organic solvents—indeed more readily than sulfur itself. 

By decomposition of ethereal solutions of heptasulfur imide with triphenyl-methyl sodium, an olive green sodium salt Na(NS7) may be prepared (17) which probably contains the ion (VI) and which, as expected, is much more reactive than S7NH itself. For example, NaNS7 undergoes hydrolysis even in contact with moist air. 

Dicyclohexylcarbodiimide in cold tetrahydrofuran added at 0° to a soln. of chloracetic acid and heptasulfur imide in anhydrous tetrahydrofuran, and kept at 0° overnight N-(chloracetyl) heptasulfur imide. Y 79%. F. e. s. J. E. Gol-chester, P. Tavs, and H. J. Schulze-Steinen, Soc. 1963, 4918. 

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