Dithionitronium hexafluoroarsenate
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| ImageFile = NS2AsF6.svg
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|Section1={{Chembox Identifiers
| CASNo = 80485-40-1
| ChemSpiderID = 9509584
| PubChem = 11334638
| StdInChI=1S/AsF6.NS2/c2-1(3,4,5,6)7;2-1-3/q-1;+1
| StdInChIKey = FHQHPTGLQAUWCS-UHFFFAOYSA-N
| SMILES = [N+](=S)=S.F[As-](F)(F)(F)(F)F
}}
|Section2={{Chembox Properties
| F = 6|As = 1| S=1|N=2
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| Appearance = yellow solid
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|Section3={{Chembox Hazards
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Dithionitronium hexafloroarsenate is the inorganic compound with the formula {{chem2|[SN2]AsF6}}. It is the hexafluoroarsenate ({{chem2|AsF6-}}) salt of S=N=S+. The cation is of interest as the sulfur analogue of nitronium ({{chem2|NO2+}}). Hexafloroarsenate is a weakly coordinating anion. According to X-ray crystallography, S=N=S+ is linear with S-N distances of 146 picometers.{{Greenwood&Earnshaw2nd}}
Synthesis and reactions
Dithionitronium hexafluoroarsenate is prepared from thiazyl chloride using silver hexafluoroarsenate.{{cite journal |doi=10.1039/DT9920003097 |title=A General Route to N(SCl)2+ and SNS+ Salts |date=1992 |last1=Ayres |first1=Bryan |last2=Banister |first2=Arthur J. |last3=Coates |first3=Philip D. |last4=Hansford |first4=Michael I. |last5=Rawson |first5=Jeremy M. |last6=Rickard |first6=Clifton E. F. |last7=Hursthouse |first7=Michael B. |last8=Malik |first8=K. M. Abdul |last9=Motevalli |first9=Majid |journal=Journal of the Chemical Society, Dalton Transactions |issue=21 |page=3097 }} The hexachloroantimonate salt can be prepared by treating thiazyl chloride with sulfur in the presence of antimony pentachloride according to this idealized equation:
: {{chem2|SNCl + S + SbCl5 -> [NS2]SbCl6}}
The dithionitronium cation reacts with nitriles to give dithiadiazolium salts:{{cite journal |last1=Rawson |first1=Jeremy M. |last2=Banister |first2=Arthur J. |last3=Lavender |first3=Ian |year=1995 |title=The Chemistry of Dithiadiazolylium and Dithiadiazolyl Rings |journal=Adv. Heterocyc. Chem. |volume=62 |doi=10.1016/S0065-2725(08)60422-5}}
:{{chem2|[NS2]+ + RCN -> [RCN2S2]+}}
Addition to alkynes gives dithiazolium salts:
:{{chem2|[NS2]+ + R2C2 -> [(RC)2NS2]+}}