Structural studies on some derivatives of mesoionic 1,2,3,4-thiatriazolium-5-aminide using multinuclear magnetic resonance and X-ray diffraction

摘要

X-ray diffraction data are reported for two mesoionic 1,2,3,4-thiatriazolium-5-aminides. The data for the thiatriazole ring are consistent with those for similar compounds published previously. The C5-N6 bond in compound 1 is about 1.26 A in length and about 1.32 A for compound 2, showing that this bond has double bond (imine) character. The N6 phenyl group adopts the cis configuration with respect to S1 in both compounds. ~(13)C, ~(14)N and ~(15)N NMR studies on six derivatives of mesoionic 1,2,3,4-thiatriazolium-5-aminide show that protonation and alkylation on N6 result in significant variation in the N2, N6 and C5 chemical shifts. Low temperature, -50 deg C, ~1H and ~(13)C NMR measurements on compounds 1 and 4 show the absence of an equilibrium between possible cis and trans isomers with respect to S1.