The dithianitronium cation

The cyclic [SaNs] cation (5.13), a six r-electron system, is the only example of a nitrogen-rich, binary S-N cation. The thermally stable salt [SaNslaiHgaCle] is obtained from the reaction of (NSC1)3 with HgCla in CHaCla. The bond lengths in the five-membered ring indicate delocalized r-bonding that is attenuated across the S-S bond. 

The [SsNa] radical cation (5.14, E = S) has been well characterized in solution by its five-line (1 2 3 2 1) EPR signal. It is prepared by oxidation of S4N4 with reagents such as AsEs or HSOsE.  

The calculated barrier to dissociation of the [S3N2] dication into [SN] and [S2N] in the gas phase is 10.9 kcal mof . However, lattice-stabilization effects allow the isolation of [MEg] salts (M = As, Sb) of this six r-electron system in the solid state from the cycloaddition of [SN] and [S2N] cations in SO2 (Eq. 5.11). ° The S-S and S-N bond distances in the planar, monomeric dication are shorter than those in the 

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Hexafluoroarsenate salts 74 and 75 are prepared from the relevant nitriles using S2NAsF6 as the source of the dithianitronium cation (SNS+). Further reaction with 2equiv of SbPh3 gives radicals 76 and 77. Such reactivity can be confirmed by ESR spectroscopy, prior to quantitative isomerism, which takes place at room temperature <1986CC140>. 

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