Dithionitronium hexafluoroarsenate

Dithionitronium hexafloroarsenate is the inorganic compound with the formula [SN2]AsF6. It is the hexafluoroarsenate (AsF6-) salt of S=N=S+. The cation is of interest as the sulfur analogue of nitronium (NO2+). Hexafloroarsenate is a weakly coordinating anion. According to X-ray crystallography, S=N=S+ is linear with S-N distances of 146 picometers.

Synthesis and reactions
Dithionitronium hexafluoroarsenate is prepared from thiazyl chloride using silver hexafluoroarsenate. The hexachloroantimonate salt can be prepared by treating thiazyl chloride with sulfur in the presence of antimony pentachloride according to this idealized equation:
 * SNCl + S  +  SbCl5  ->  [NS2]SbCl6

The dithionitronium cation reacts with nitriles to give dithiadiazolium salts:
 * [NS2]+ + RCN  ->  [RCN2S2]+

Addition to alkynes gives dithiazolium salts:
 * [NS2]+ + R2C2  ->  [(RC)2NS2]+