N-15, N-14, C-13 AND H-1-NMR STUDY OF MESOIONIC METHYLIDES AND THIOCARBONYL YLIDES WITH A 2,3-DIPHENYLTETRAZOLIUM RING

N-15, N-14, C-13 and H-1 NMR data were collected for the identificatio n and structure determination of several mesoionic 2,3-diphenyltetrazo lium methylides (1) and mesoionic thiocarbonyl ylides (2) with a 2,3-d iphenyltetrazolium ring. In solution, mesoionic thiocarbonyl ylides ca n exist as either a cyclic form or a mesoionic cyclic form (2) dependi ng on the solvent and on the exocyclic group, whereas the mesoionic 2, 3-diphenyltetrazolium methylides exist rather as a cyclic mesoionic fo rm (1). The NMR data indicate that the 2,3-diphenyltetrazolium methyli des and the mesoionic thiocarbonyl ylides in CF3COOH solution are prot onated at the exocyclic group.