Electron transfer cyano-bridged complexes

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 preparation and properties of a number of cobalt(III)-cyano complexes are given in Table 8. Many reactions involving formation of cobalt(III)-CN bonds are catalyzed by cobalt(II) species. Adamson first proposed that catalysis of cyanide substitution in [CoXCNKj) ] " ions (X = Br , I ) to form [Co(CN)5X] involved the participation of tlie substitutionally labile [Co(CN)5] (Scheme 5). Subsequent mechanistic studies have been interpreted in terms of inner-sphere electron transfer between [Co(CN)5] and [CoX(NH3)5] through bridged [(NC)5CoXCo(NH3)5] intermediates (X = Cl , , NCS , OH ). For a number of other pentaamminecobalt(III) complexes,... 

---