The reaction of bicyclic sulfur-nitrogen heterocyles RCN5S3 (R = F3C, Ph, Me2N, 2-FC6H4, 2,6-F2C6H3) with [Hg(SO2)(2)][AsF6](2) in liquid SO2 yielded the corresponding trithiatetrazocinium-hexafluoroarsenates (RCN4S3][AsF6] as yellow solids and a red-brown insoluble byproduct with the approximate composition Hg3N2. Single crystal structure determinations of the salts and theoretical calculations on the trithiatetrazocine cations [RCN4S3](+) revealed the cations to be planar eight-membered heterocycles. The [RCN4S3](+) Cations are the missing link in the series of known valence isoelectronic eight-membered 10 pi azocines, that is, [S4N4](2+) and RC(NSN)(2)CR. In contrast to neutral trithiatetrazocines and dithiatetrazocines RC(NSN)(2)CR carrying donor substituents, which have a folded butterfly structure with a transannular S-S bond, the positive charge on the [RCN4S3](+) Cations always stabilizes the planar structure independent of the nature of the substituent. Experimentally obtained structures and theoretical calculations (geometries, frequencies, charges, nucleus-independent chemical shifts (NICS)) are in agreement with the description of [RCN4S3](+) as planar eight-membered 10 7 Huckel aromatic. The single crystal structure determinations of some 3,5-R-1,2,4,6-thiatriazinyl hexafluoroarsenates (R = Ph, 2-FC6H4, 4-FC6H4), which were isolated from the above reaction as well, are also included.