Reductive activation of arenes 20.* Anionic products of two-electron reduction of tolunitriles in liquid ammonia: the nature and electronic structure

Stable cyanomethylcyclohexadienyl anions generated in two-electron reduction of isomeric tolunitriles by potassium in liquid ammonia were detected by NMR spectroscopy. The chemical shifts in these anions were obtained from density functional (PBE/3z) quantum chemical calculations and the electron density distributions for the anions were calculated in the framework of the NBO approach at the HF/6-31+G* level of theory. The experimental and calculated δ C values are in good agreement. Changes in the δ C values on going from the starting nitriles to the corresponding anions are linearly related to the calculated π-electron densities on the pentadienyl ring carbon atoms.