SYNTHESIS AND STRUCTURE OF SALTS OF THE BICYCLIC SULFUR-NITROGEN CATION S4N5+ AND A COMPARISON OF THE ELECTRONIC-STRUCTURES OF THE TETRASULFUR PENTANITRIDE(1+) AND PENTANITRIDE(1-) IONS

The new sulfur-nitrogen halide S4N5Cl; has been prepared in good yield from trithiazyl trichloride, S3N3Cl3, and bis-[(trimethylsilyl)imido]sulfur, Me3SiN=S=NSiMe3, in carbon tetrachloride. An X-ray structural determination of this compound shows it to have a polymeric, predominantly ionic, structure in which bicyclic S4N5+ cations are symmetrically bridged by Cl- ions. Crystals of S4N5Cl are orthorhombic and belong to the space group Pnma with a = 17.491 (17) Å, b = 7.819 (2) Å, and c = 4.838 (4) Å, V = 661.7 (5) Å3, Z = 4, and Dc = 2.346 g cm-3. The structure was solved by direct methods and Fourier techniques and refined to a conventional R factor of 0.066 for 1162 independent reflections with I ≥ 3σ(7). The reaction of S4N5Cl with silver(II) fluoride or antimony pentachloride gives S4N5F or S4N5SbCl6, respectively. The vibrational spectra of these salts of the S4N5+ cation are reported. Ab initio Hartree-Fock-Slater SCF calculations have been carried out for S4N5+ and for the related anion S4N5- in order to compare their ground-state electronic structures with that of S4N4, and, in particular, to assess the importance of S--S interactions within these S-N cages. These calculations show that the introduction of a bridging N‘ entity into the S4N4 framework destroys one of the transannular S--S bonds and weakens the S-N framework bonds. In S4N5+ there are no S--S bonds, as expected for loss of 2 electrons from the S4N5- anion. © 1979, American Chemical Society. All rights reserved.