Sulphur–nitrogen anions: formation from azide ion and elemental sulphur and their role in the synthesis of cyclic sulphur imides

Abstract

The reaction of azide ion with cyclo-octasulphur in tris(dimethylamino)phosphine oxide produces the [S₄N]^– ion, whereas lithium nitride yields the trisulphur radical ion, S₃^–·, predominantly. The azide reaction provides a convenient and direct synthesis of S₇NH. PO(NMe₂)₃ Is superior to NN-dimethylformamide (dmf) as a solvent for the S₂Cl₂–NH₃ route to cyclic sulphur imides. Equilibria of the type [S₇N]^–⇌[S₄N]^–+⅜S₈⇌½[S₆N₂]^2–+½S₈ are invoked to explain the formation and relatively low yields of S₆(NH)₂ isomers in these syntheses.