The impact of cation structure upon the acidity of triazolium salts in dimethyl sulfoxide.

A series of triazolium salts, selected for their varying electronic and steric properties, were prepared and their pKa values were determined in DMSO at 25 °C using the bracketing indicator method. The effect of each systematic structural variation upon the acidity of the triazolium cation has been considered, in particular examining the effects of systematically altering electronic properties, quantified through the use of Hammett σ parameters. The first pKa value for an azolium salt that generates a mesionic carbene is also reported. These new data allow for the selection of appropriate bases for the deprotonation of such triazolium salts and the potential to correlate the pKa values determined herein with the nucleophilicity of the corresponding carbenes.