Tetraphenylhydrazine cation radical

X may be NR2, SR or OR. The name is derived from the violet color of the tetraphenylhydrazine cation radical [8 + n = zero, X = N(C6Hs)2]. This, like all of the violenes is a markedly stable cation radical. In fact, the violenes are often made by oxidation of M by M2+, and the equilibrium thus achieved is called comproportion-ation (95). Comproportionation constants (96) have been obtained... 

The most studied example of II was tetraphenylhydrazine cation radical, whose purple color led Hiinig to coin the term "violenes" ( ) for the series of vinologous species his group has studied extensively (3). The solution ESR spectrum of hydrazine radical cation had been recorded in a flow system (4). Aromatic examples of III had received extensive study (5), and diphenyl-picrylhydrazyl was the first example of a neutral radical stable both to dimerization and reaction with oxygen. The chemistry of 1,1-dimethyldiazenium cation had been studied (6), and interesting electrochemical work on arylhydrazine oxidations had been carried out by Cauquis and Genies (7). 

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