Crystal and molecular structures of sydnones, 4,5-diphenylisosydnone, and mesoionic tetrazoles

The crystal and molecular structures of 3-(2-aminophenyl)sydnone (3b), [1,2,3]oxadiazolo[4,3-c][1,2,4]benzotriazinium-3-olate (1), 4,5-diphenylisosydnone (6), 1,3-diphenyltetrazolium-5-thiolate (2a), and 2,3-diphenyltetrazolium-5-olate (10b) have been determined X-ray crystallographically. The molecular parameters of the sydnone derivatives and of (6) are in accord with open-chain structures rather than with a conventional mesoionic formulation. The C-S bond length of (2a) is very close to the reported value for the isomeric dehydrodithizone whilst the C-O distance in (10b) is in the region normally observed in amides.