[10025-67-9] · Cl2S2 · Disulfur Dichloride · (MW 135.04)
Alternate Name: sulfur monochloride.
Physical Data: mp -77 °C; bp 138 °C; d 1.688 g cm-3; nD20 1.6700.
Solubility: sol benzene, ether; readily sol CS2.
Form Supplied in: golden yellow, oily liquid; pungent odor; fumes in moist air; impure sample can be reddish orange due to SCl2; commercially available.
Purification: distillation of 500 g from 20 g of sulfur and 5 g of charcoal; fraction from 135 to 137 °C is collected.
Handling, Storage, and Precautions: refrigerate in dark bottle; air and moisture sensitive; incompatible with acids, bases, alcohols, and amines. Avoid contact with metals; harmful if swallowed; inhalation may be fatal. Use in a fume hood.
Based on the resulting tautomers from a synthesis of hindered N-thiosulfinylanilines (Ar-N=S=S) from anilines (eq 1),4 a synthesis for thioketones and thioaldehydes has been worked out from hydrazone derivatives and S2Cl2.5
Hydrazone derivatives are treated with S2Cl2 to produce an N-thiosulfinylamine which undergoes cyclization, followed by molecular extrusion of N2 (g) to give an S-thioxothioketone. The S-thioxothioketones (R2C=S=S) are not isolable, as they decompose to the thioketones and sulfur (eq 2).2,6 The yield of 2,2,4,4-tetramethylthiopentanone is the isolated yield; spectra showed near quantitative conversion.
2,4,6-Tri-t-butylthiobenzaldehyde was the first stable thiobenzaldehyde synthesized. It was prepared from the corresponding hydrazone in 40% yield using S2Cl2 in the presence of Triethylamine (eq 3). In the absence of oxygen, no decomposition was observed after 1 year at rt in the solid phase. In the presence of air, it is quantitatively converted to 2,4,6-tri-t-butylbenzaldehyde.7
Treatment of unsaturated oxime derivatives with disulfur dichloride in the presence of Hünig's base gives high yields of cyclopenta-1,2,3-dithiazoles (eq 4).3 Treatment of saturated oximes such as cyclopentanone oxime gives unsaturated, perchlorinated dithiazoles (eq 5) in significantly reduced yield.
Disulfur dichloride adds to alkenes to form b-chloroalkyl mono-, di-, and trisulfides. The monosulfides, however, cannot be converted into episulfides. Their production is minimized by the addition of dichloropolysulfanes, S
Disulfur dichloride can also be used to synthesize N,N-dithiobissulfoximines,7 to synthesize macrocyclic, polysulfur compounds,8 and is part of an extremely powerful chlorinating agent for perchlorination of aromatic systems (see also Aluminum Chloride and Sulfuryl Chloride).9 It is also a reagent for the synthesis of aranotins, a small group of sulfur-bridged diketopiperazines,10 and it was tried in conjunction with sulfur dichloride for one-step episulfide synthesis.11
Brian C. Austad
University of Wisconsin, Madison, WI, USA