Structural studies on some 1,3,4-thiadiazolium-2-aminides and their rearrangement isomers using 15N and 13C NMR spectroscopy

Abstract

15 N and 13C NMR data are reported for some triaryl-1,3,4-thiadiazolium-2-aminides, I, (both as free bases and as hydrochloride salts) and for their rearranged 1,3,4-triazolium-2-thiolate, II, free base isomers. The structures of the compounds and their interconversion processes have thereby been re-studied. The 1J(13C–15N) coupling constants have proved to be the most direct means of differentiating the isomeric structures. Nitrogen CPMAS NMR studies of I, as their hydrochlorides, and II using 15N natural abundance, show that protonation takes place on the exocyclic NHPh moiety in the former series. 13C CPMAS NMR studies show that I can undergo isomerization to II in the solid state.