Chemical Reactivity of Tetrasulfur Tetranitride: Synthesis, Physical Properties, and Structural Characterization of the Amorphous Phase Cu₇S₄N₄

Abstract

Tetrasulfur tetranitride, S4N4, reacts with elemental Cu within inert solvents to a black‐blue material of approximate composition Cu7S4N4 which is totally amorphous to X‐rays and which cannot be made crystalline by either thermal treatment or electron radiation. Cu7S4N4 explodes if heated above 234 °C or when subjected to mechanical shock to eventually yield copper(I) sulfide; this together with the characteristic infrared spectrum of Cu7S4N4 indicates the presence of molecular S4N4 units inside the amorphous phase. The metastable nature of Cu7S4N4 is also mirrored by electron microscopy which furthermore allows the structural characterization of its degradation products. Based on experimental EXAFS data offering characteristic Cu—N and Cu—S distances, a theoretical crystalline approximant of Cu7S4N4 was suggested and structurally optimized by density‐functional total‐energy calculations including periodic boundary conditions. This model incorporates a central S4N4 unit bonded to three shells of Cu atoms of different functionalities; in addition, a partial rupture of the S4N4 unit is likely to allow for a lowering of the total energy of the metastable phase. The latter observation supports the impossibility to make Cu7S4N4 crystallize using 4N4 crystallize using whatever kind of measures.

Synthesis and X-Ray Crystal Structure Determination of Thiotrithiazyl Iododichloride, S4N3ICl2

“…In the course of our systematic studies on the temperature-dependent crystal structures [8] and chemical reactivity [9] of tetrasulfur tetranitride, we have reinvestigated the above mentioned reaction starting from S 4 N 4 and liquid ICl. Here we report in detail about the synthesis and X-ray crystal structure analysis (Rietveld technique) of S 4 N 3 ICl 2 .…”