Influence of the coordination-number of nitrogen on the structure of 6a-lambda(4)-thia-1,3,4,6-tetraazapentalenic systems - crystal-structure analyses of 3-(2-pyridylimino)-3h-[1,2,4]thiadiazolo[4,3-a]pyridine and its 1-methylated salt
Journal of heterocyclic chemistry vol:29 issue:7 pages:1765-1768
Structural data were obtained by X-ray crystallography for the title compounds which show that they are essentially planar and exhibit an approximately linear N2-S1-N8 arrangement. In compound 3 the separation between the sulfur atom and the pyridine nitrogen atom (2.61 angstrom) is larger than the Huggins constant energy distance (2.58 angstrom), suggesting that there is little or no bonding between them. The methylated salt 4, on the contrary, has a closer S...N(pyridine) distance (2.19 angstrom) with an estimated bond dissociation energy of 6 kcal/mole.