Electrochemical Studies of the Reduction of Fluorenone Triphenylphosphazine. Formation of the Stable Dimeric Dianion, (FlN2)2(2-)

Article abstract of DOI:10.1021/ja00347a004

The electrochemical reduction of fluorenone triphenylphosphazine (Fl=NN=PPh3) in N,N-dimethylformamide - 0.1 M (n-Bu)4NClO4 is initially a one-electron process which affords the corresponding anion radical.Fl=NN=PPh3(-*) is unstable on the cyclic voltammetric time scale, decomposing by nitrogen-phosphorus bond cleavage (k = 0.45 s^-1 at T = 1 deg C) to give PPh3 and 9-diazofluorene anion radical (FlN2(-*)).The latter species then reacts rapidly with either FL=NN=PPh3 or FlN2(-*) to give a stable dimeric dianion.The dianion, which was shown from chronoamperometric and coulometric gas-pressure studies to have the empirical formula (FlN2)2(2-), is oxidized in successive one-electron steps to (FlN2)2 which slowly loses N2 on the cyclic voltammetric time scale to give fluorenone azine (Fl=NN=Fl).The structure of the dimeric species is considered to be the tetraazatriene Fl=NN=NN=Fl.No evidence was obtained for the formation of the carbene anion radical, Fl(-*), via the loss of N2 from FlN2(-*).