THE ENERGETICS OF FORMATION AND X-RAY CRYSTAL-STRUCTURE OF SNSNS(ASF6)2, CONTAINING THE LATTICE-STABILIZED AROMATIC 6-PI 1,3,4,2,5-TRITHIADIAZOLIUM(2+) CATION FORMED BY THE CRYSTAL-LATTICE-ENERGY-DRIVEN, SYMMETRY-ALLOWED CYCLOADDITION OF SN+ AND SNS+

We report the preparation, vibrational spectra and X-ray crystal structure of activated SNSNS(AsF6)2,, containing the 6-pi 1,3,4,2,5-trithiadiazolium(2+) cation, which dissociates in solution to SN+ and SNS+, consistent with ab initio 6-31G* calculations (estimated gas-phase dissociation enthalpy: -400 kJ mol-1); the activated SNSNS2+ ring represents a local energy minimum, and the cycloaddition of SN+ and SNS+ is driven in the solid state by the high lattice energy of the 1:2 salt.