Third Time is a Charm – Protonating Tricarboxybenzenes

Abstract

Triprotonation of the three constitution isomers of tricarboxybenzene was accomplished. Furthermore, the preparation of selected mono‐ and dications showed the sequence of protonation steps. The cations were mostly isolated as [SbF6] and [AsF6] species, which were characterized by Raman and NMR spectroscopy as well as X‐ray structure determination. To further elucidate the experimental results, quantum chemical calculations are employed, especially in regard to charge distribution with NPA charges and aromaticity by NICS(0) values. Thermal decomposition of the compounds was investigated in order to explore the possibility of acyl cation formation. The influence of the aromatic system, substitution pattern and anomeric effect concerning the properties of the respective compounds was thus explained.

Two Roomtemperature‐stable Trications – Triprotonated Triamino‐ and Tricyanobenzene

“… Triprotonated 1,3,5‐tricarboxybenzene (left) [5] and 1,3,5‐tricyanobenzene (right) with selected bond lengths (Å) of the neutral compound (red) and triprotonated species (black). …”

“…Protonation of various nitriles, [3] for example of benzonitrile and terephthalonitrile, was easily achieved and led to the respective nitrilium species. [4] With the protonation of 1,3,5-tricarboxybenzene, [5] we wanted to investigate the protonation of other 1,3,5-substitued benzenes, but with nitrogencontaining functional groups (Figure 1). 1,3,5-triaminobenzene is fascinating, as its monoprotonation results in a temperature-dependent equilibrium (Scheme 1).…”