Biferrocene picrate

The differences between biferrocenium and l,r-biferrocene[Fe(n)-Fe(in)] cations have been previously discussed [57]. It is sufficient to note here that the crystal structure of l,r-biferrocene[Fe(ii)-Fe(in)] picrate [61a] reveals a shorter Fe-Fe distance than that in the neutral compound [61b] (3.64 vs. 3.98 A) indicating increased interaction between the two metal centers in the cation. Possibly because a high yield synthesis of 1,1 -biferrocenylene is not available, and because the derivative chemistry of this compound is essentially undeveloped, no other relevant studies directed toward the preparation of molecular materials based on it have appeared in the literature. 

The introduction of mixed valence states can also induce semiconductivity. Cowan and Kaufman (10, 11) demonstrated that the conductivity of biferrocene [Fe(II)Fe(III)] picrate, 4, was six orders of magnitude greater than that of biferrocene, 3, itself. Could this be extended to polymeric systems We previously reported 12) the synthesis of mixed valence [Fe(II)Fe(III)] polyvinylferrocene and polyferrocenylene systems with significantly enhanced conductivities (10 -10 Q cm ) as compared with the [Fe(II)Fe(II)] analogs (10 Q cm ). 

An example of the former is seen in Hg(C9H7)Cl, which exhibits an aromatic CH stretching at 3060-3050 and an aliphatic CH stretching band at 2920-2850 cm The latter band should be absent in the jr-bonded complex Infrared spectra are reported for a mixed-valence-state complex, biferrocene (Fe, Fe ) picrate and bis(pentalenyl)Ni, whose structures are shown in Fig. IV-iifl and iV-llb, respectively. The spectrum of a triple-decker compound, [Ni2(Cp )i]BF4 (Cp CH3-CP) (Fig. IV-iic), is similar to that of Ni(Cp )2." ... 

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