Charge-Transfer Complexes of Polyalkylated Ferrocenes

Before turning our attention to alkylated ferrocenes, it is worthwile to discuss some of the few CT complexes reported for the parent compound, Cp2Fe. In a 1962 paper 

The CT complex [Cp2Fe][TCNE] was found to decompose in solution, not only affording the neutral congeners, but also other species. This is due to the complex chemistry of the TCNE radical anion [18]. For example, when equivalent amounts of ferrocene and TCNE are allowed to react in warm ethyl acetate, [CpzFeJ. s [(NC)2C = C(CN)0] is formed in good yield [21]. This material was characterized by X-ray crystallography and found to contain the anion tricyanoethenolate, which was shown to be formed from [TCNE] in the presence of oxygen (Fig. 8-2). The stoichiometry of this CT complex is also quite unusual and it is best described as a ternary phase of the type [D ][Do.5A ]. 

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