Diazenes electron transfer

The high lability of bound N2 in [FeII(CN)5N2]3 regenerates the active site, namely the [FeII(CN)5H20]3 ion, which is able to further bind and process hydrazine. A more detailed kinetic study could be warranted for this interesting set of reactions. Some uncertainties still remain as to the nature of the intramolecular electron-transfer rate processes (91). At the employed concentration levels of the complex, the participation of mixtures of mononuclear and dinuclear complexes complicate the spectral evolution. Even the nature of the dinuclear intermediates (cyano- or hydrazino-bridged) could be put into question (probably both are involved, due to the labile interconversion equilibria). The participation of Fe(III) species, either in the mononuclear or dinuclear species, as reactive intermediate precursors of the formation of diazene and N2... 

The oxidation of l-phenyl-2-(4-methylphenyl)diazenes, 4 -substituted with a dimethylamino or methoxy group, with ferric chloride resulted in the generation of radical cation by a single electron transfer. It has been proposed that an electron, in the first step of oxidation, is extracted from the azo and/or from the amino nitrogen atom.68... 

It can be conceived that intramolecular electron transfer from N2H2 to the Fe(III) centers, cleavage of NH bonds, and formation of SH bonds converts 44 into 45, which is a doubly protonated N2 complex. Deprotonation of 45 would yield the neutral N2 complex 46. The reversal of this sequence would convert 46 into 43 and realize the first 2 H+/2 e reduction step of N2 fixation. Twofold protonation of 46 gives 45 in which all atoms necessary to form the neutral diazene complex 43 have already taken their positions. The above mentioned anodic redox potential shift upon protonation (cf. Section IV.F) could enable us to reduce species C at relatively mild redox potentials, in contrast with the neutral species 46, which might be irreducible when it is an 18 VE complex. 

Chemically, methods for deoxygenation and reductive deamination have seen additions in the last two decades which depart from those traditional approaches using hydride reduction of activated alcohols and diazene generation from aliphatic amines. New methods for amine activation, new complex hydrides and, in particular, methods using electron transfer and free radical processes have greatly expanded the range of substrate molecules which can be subject to efficient functional group removal. 

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