Crystal structure of a new crystalline modification of tetra-arsenic tetrasulphide(2,4,6,8-tetrathia-1,3,5,7-tetra-arsatricyclo[3,3,0,03,7]-octane)

The crystal structure of the title compound was determined from photographic data and solved by direct methods. 598 Unique reflections were refined by least-squares methods to R 0·104. Crystals are monoclinic, space-group C2/c, with a= 9·957, b= 9·335, c= 8·889 Å, β= 102·48°, Z= 4. The molecules possess D2d(2m) symmetry within experimental error. Mean bond lengths and angles are: As–As 2·593, As–S 2·243 Å S–As–As 99·1, S–As–S 94·4, and As–S–As 101·2°. The Raman spectra of α- and β-As4S4 are presented; the molecules may polymerise on prolonged laser irradiation.