An X-ray study of two 1-thia-2,3,4-triazolo-5-methylides

X-ray diffraction data are reported for two 1-thia-2,3,4-triazolo-5-methylides: I C22H15N3O2S, Pbca, a = 19.567(5) Angstrom, b = 8.197(2)Angstrom, c = 23.299(5) Angstrom, V = 3737.0(16) Angstrom(3), Z = 8; II C13H13N3O3S, C2/c, a = 11.605(3) Angstrom, b = 22.230(2) Angstrom, c = 11.579(2) Angstrom, beta = 107.94(2)degrees, V = 2841.9(9) Angstrom(3), Z = 8 The results reveal charge separation between the thiatriazole ring and the exocyclic group, accompanied by partial delocalization of the positive charge over the thiatriazole ring. The geometrical features of the heterocyclic rings in the two compounds are very similar to each other and to those found in analogous compounds. In both structures the geometry of the exocyclic group suggests delocalization of the negative charge directed mainly towards the C = O bond being cis with respect to the ring sulphur atom, resulting in a partial negative charge delta(-) on the oxygen atom. (C) 1998 Elsevier Science B.V.