X-RAY CRYSTAL-STRUCTURES OF THE 1,3,2-BENZODITHIAZOLYL DIMER AND 1,3,2-BENZODITHIAZOLIUM CHLORIDE SULFUR-DIOXIDE SOLVATE - COMPARISON OF THE MOLECULAR AND ELECTRONIC-STRUCTURES OF THE 10-PI-ELECTRON C6H4S2N+ CATION AND THE C6H4S2N. RADICAL AND DIMER AND A STUDY OF THE VARIABLE-TEMPERATURE MAGNETIC-BEHAVIOR OF THE RADICAL

The X-ray crystal structures of the 1,3,2-benzothiazolyl dimer, (C6H4S2N)2 [(3*)2], and 1,3,2-benzothiazolium chloride sulfur dioxide solvate, C6H4S2N+Cl−SO2, are reported. Crystal data: C6H4S2N+Cl−SO2, orthorhombic, space group Pnma, a = 7.9765 (6) Å, b = 8.8471 (6) Å, c = 13.6309 (8) Å, V = 961.9 (2), Å3, Z = 4; C6H4S2N*, orthorhombic, space group Pbca, a = 7.6929 (3) Å, b = 16.0396 (7) Å, c = 10.3863 (5), Å, V = 1281.6 (2) Å3, Z = 8. The structures were solved by multan-80 and were refined to final R values of 0.040 and 0.030, respectively. The crystal structure of C6H4S2N+Cl−SO2 consists of discrete, planar cationic units, chloride anions, and SO2 molecules, with significant contacts between the anion and the SO2 molecule, implying some (SO2Cl−)n character, and the sulfur centers of the cation, giving a two-dimensional polymeric macrostructure. The cen- trosymmetric 1,3,2-benzodithiazolyl dimer contains two C6H4S2N units joined by two long S–S bonds [3.175 (1) Å], with interplanar spacing of 3.0 Å between the two C6S2 mean planes. The C6S2 segment of the monomeric unit is planar with the nitrogen atom displaced by 0.186 (2) Å above this plane away from the center of symmetry. The dimers are linked by very weak S—S contacts [3.477 (1), 3.781 (1) Å] into a sheetlike infinite two-dimensional net. Variable-temperature magnetic susceptibility measurements show the solid to be essentially diamagnetic, but on melting the compound becomes paramagnetic (μ(87 °C) = 1.54 μB). On this basis C6H4S2N* is classified as a paramagnetic liquid. The electronic structures of the radical/cation systems C6H4S2N and HCSNSCH are examined at the ab initio STO-3G level and differences in the experimental geometries of the corresponding cations accounted for. C6H4S2N+ is shown to be a heteronaphthalenic system, and all the structural differences between the radical and cation are completely rationalized in terms of the nature of the SOMO of 3*, which is based primarily, but not exclusively, on the SNS region of the molecule. The dimeric structure of (3*)2 is modeled by CNDO/2 calculations on (HCSNSCH)2, and (3*)2 is classified as a π*–π*dimer of radical monomers. Distortions from planarity of 3* within (3*)2 are rationalized by relative energy calculations, which imply easy deformation of the SNS moiety. © 1990, American Chemical Society. All rights reserved.