A STRUCTURAL STUDY OF SOME MESOIONIC TYPE-A OXA-TRIAZOLES AND THIATRIAZOLES IN THE SOLID-STATE BY CP-MAS NMR AND X-RAY CRYSTALLOGRAPHY

C-13 and N-15 CP-MAS NMR measurements are reported for four mesoionic type A oxa- and thiatriazoles. X-ray structures are also reported for compounds 1 and 2. The results obtained show close similarity between the solid and solution structures for these molecules. The phenyl and mesoionic rings are nearly coplanar and the bond orders of the C5-Y- b onds are close to 1.5. The relative cis and trans positions of the com ponents of the exocyclic groups, with respect to the mesoionic ring su lphur atom, are also reported.