An experimental and computational investigation of the formation and structures of N-hydro and N,N'-dihydro-benzo-2,1,3-chalcogenadiazolium chlorides

The conjugate acids of benzo-2,1,3-selena- and benzo-2,1,3-telluradiazole are the simplest members of the family of N-substituted chalcogenadiazolium cations. Four crystalline phases that in principle contain such molecular ions were isolated and structurally characterized: CH(NH)TeCl, [CH(NH)][CH(NH)TeCl]Cl, CHN(NH)SeCl and CHN(NH)SeCl · 1/2 [HO]Cl. The stepwise protonation of benzo-2,1,3-teluradiazole in DMSO solution was monitored by H NMR, providing an estimate of the basicity of this molecule relative to pyridine. While most of the structures are consistent with the chalcogen in oxidation state II, the molecular geometry of CH(NH)TeCl is suggestive of oxidation state IV. The relationship between the two structural types was examined with DFT calculations.