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.