Tetrasulphur dinitride; its preparation, crystal structure, and solid-state decomposition to give poly(sulphur nitride)

Abstract

The reaction between cyclotetrathiatriazenium chloride (S₄N₃Cl) and zinc sulphide induced by zinc is a convenient small-scale method of preparing tetrasulphur dinitride. A second method was used to obtain crystals for X-ray analysis; vapours from S₄N₃Cl, thermolysed at 130 °C, were passed over silver selenide at 180 °C. The condensed product (after polymerisation of the S₂N₂ content at –5 °C) gave transparent red crystals of S₄N₂, space group P4₂nm with a= 11.25(1), c= 3.836(4)Å, and Z= 4. The molecules are non-planar rings with m symmetry; S(1) and S(2) lie on the mirror plane. Distances are S(2)–S(3) 2.055(3), S(1)–N 1.561(8), and S(3)–N 1.661 (8)Å. There is a close intermolecular contact, S ⋯ N 3.015 Å. The slow decomposition of S₄N₂ crystals at 263 K is accompanied by polymerisation to fibrous (SN)_x. The likely mechanism of the polymerisation is identified.