Comparative ab initio calculations on several salts

Ab initio calculations performed on three anions, substituted by strong electron withdrawing groups CF3SO2, brought useful information on the anion geometries and stabilities as well as on the charge delocalization. Thus the carbanion exhibits a planar optimized geometry while, according to HOMO values, the stability vs. oxidation is best for the imide anion. Moreover the absolute hardness, calculated from the HOMO and LUMO energy levels, show that this latter is the hardest base among the three previous anions.