Crystalline Cyclic (Alkyl)(amino)carbene-tetrafluoropyridyl Radical.

A stable cyclic (alkyl)(amino)carbene (CAAC) 1 inserts into the para-CF bond of pentafluoropyridine, and after fluoride abstraction, the iminium-pyridyl adduct [3](+) was isolated. A cyclic voltammetry study shows a reversible three-state redox system involving [3](+) , [3](⋅) , and [3](-) . The CAAC-pyridyl radical [3](⋅) , obtained by reduction of [3](+) with magnesium, has been spectroscopically and crystallographically characterized. In contrast to the lack of π communication between the CAAC and the pyridine units in cation [3](+) , the unpaired electron of [3](⋅) is delocalized over an extended π system involving both heterocycles.