Iron complexes ferrocene derivatives

All known pentafluorophenylgold(I) iron complexes are derivatives of ferrocene. In fact, they are obtained mainly by reaction of [Au(CgF5) (tht)] with modified ferrocenes... 

Bis(cyclopentadienyl)iron derivatives, ferrocenes, are remarkably stable against heat and air and undergo various kinds of chemical reactions. They are usually prepared by the reaction of FeCh with an alkali metal salt of cyclopentadienyl or cyclopentadiene in the presence of base [51]. Although ferrocene derivatives basically have chemical reactivities similar to those of aromatic compounds, they have found only limited applications to organic synthesis so far. However, because chiral ferrocenylphosphines are capable of having both planar chirality and an asymmetry in the side chain in their rigid framework, they have been used recently in a number of asymmetric reactions. In this section, synthesis and developments of monocyclopentadienyl complexes and ferrocenylphosphines are described. The general chemistry of ferrocenes and half metallocene complexes is reviewed elsewhere [52-53]. 

There is a large class of iron organometallic compounds which can be described as molecular, diamagnetic, and highly covalent. They are derived in the main from the parent compounds iron pentacarbonyl, Fe(CO)s, and the cyclopentadienyl complex ferrocene, (jr-CsHslaFe or CpaFe. In view of their large numbers, it is not surprising that considerable Mossbauer spectral data are available, but as we shall now see the interpretation of this data introduces considerable problems. 

Photochemical studies of iron-group metallocene substrates have received much attention, e.g. quenching of excited uranyl ion luminescence, formation of charge-transfer complexes with TCNE, redox reactions of octamethyl-ferrocene and of carboxylate anions of the types FcCOj and Fc(X)COr (X = saturated or unsaturated alkyl chain). Enzyme-catalysed one-electron oxidation of ferrocene derivatives has also been studied. Ferrocene-ferricenium cation redox systems have been incorporated into electrochemical and photo-electrochemical cells, and have found use for catalysis of photo-addition of MeOH to Bu NCO. Inter-valence electron-transfer properties of partially oxidized Fc(C C)nFc ( = 0—2), meso-tetraferrocenylporphyrin, and poly(vinylferrocene) have been assessed. 

Nitrate reductases (NaR) with an iron-sulfur center are used for nitrate conversion. Generally, nitrate is enzymatically reduced and NaR is in the oxidized form, which can be electrochemically reduced. However, the direct electron transfer between an enzyme and an electrode is strongly limited due to the fact that (1) the distance between the electrode surface and the redox active site of the enzyme, which is normally inside the globular protein, is large and (2) the orientation of donor to acceptor sites depends on the method of the immobilization of the enzyme at the electrode.Thus, low molar mass redox mediators including qui-nones, metal complexes, ferricyanide, derivatives of ferrocene, and organic redox dyes " have been used to facilitate the electron transfer between electrode and enzyme (Fig. 11.5). 

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