The cyclotetrathiazyl dication

The [S4N4] cation was first reported in 1977. It is prepared by the oxidation of S4N4 with an excess of a Lewis acid, such as SbCls or AsFs, or with S2O6F2 (Eq. 5.13).  

The [S4N4] cation 5.18 is a planar eight-membered ring with equal S-N bond lengths ( 4 ) of ca. 1.55 A. It is a fully delocalized ten r-electron system with a strong r-network.  

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