Ferrocenes as Ligands in Metal Complexes

As mentioned in Chapter 4, Section 1, to date, several hundred ferrocene derivatives have been synthesized. A further increase in their number has occurred in recent years due to the use of ferrocene derivatives as ligands in metal complexes.2 Since some examples of metallic centres branched by several ferrocene units have already been presented in Chapter 4, Section 1.4.2 (when dealing with dendrimers), we will limit our discussion 

Exhaustive oxidation at the first process makes the original orange solution assume an intense green colour typical of ferrocenium species. One may thus assume that the first oxidation is centred on the ferrocenyl unit and, therefore, the second process must be attributed to the Mo(II)/ Mo(III) oxidation. 

Once again there are two oxidation processes but, as can be inferred from the relative peak heights, a two-electron oxidation (E 2+ = +0.60 V) should precede a one-electron process CE +/3+ = +0.80 V). Based on the stoichiometry of the compound, it is naively deduced that in this case the simultaneous oxidation of the two Mo(II) centres precedes the oxidation of the central ferrocene unit. This not only means that there is no electronic interaction (communication) between the two 

It is useful to note that the precursor [(C5H5FeC5H4)CCo3(CO)9] also exhibits the expected ferrocenyl-centred oxidation, but only a single one-electron reduction.2 This means that the actual two one-electron 

Let us now consider a few complexes in which a central metal fragment is interposed between two ferrocenyl units. 

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