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.