Synthesis and crystal structure of (S3N3O4)2S, a compound with two six-membered rings bridged by a sulphur atom

The compound S4N4O2 reacts with SO2 under mild conditions to yield (S3N3O4)2S, a new bicyclic system with a skeleton consisting only of sulphur and nitrogen atoms. Crystals of this compound are tetragonal, space group P21m, with a=b= 1 183.8(2), c= 493.5(1) pm, and Z= 4. The structure has been refined to R= 0.027 for 637 unique observed reflexions. The molecule possesses crystallographic mm symmetry, with both mirror planes passing through the sulphur atom which links the two six-membered rings. The bond lengths and angles are consistent with the presence of localised sulphur–di-imide (–NSN–) units, the remaining sulphur–nitrogen bonds being essentially single bonds.