Crystalline ferrocene complexes

A variety of other organic polymers with metallocene-containing side-groups have been synthesized. However, very few of the materials have been as well studied as PVEc. Crystalline organometallic complexes containing ferrocene... 

First examples of second-sphere coordination adduct between a CD and such organometallic complexes were observed with the ferrocene and its derivatives. Thus, Breslow was the first to report in 1975 that ferrocene forms a 1 1 adduct with the /3-CD in both A/T-dimethylformamide and dimethyl sulfoxide. Nevertheless, the first crystalline inclusion complexes of ferrocene and its derivatives were prepared by Harada and Takahashi in 1984. The inclusion complexes were obtained by direct addition of crystals of ferrocene or its derivatives into aqueous solutions of CD. The stoichiometry of the inclusion complexes was found to be dependent on the sizes of the CD. The /3-CD and y-CD formed 1 1 stoichiometric inclusion complexes whereas a-CD formed a 2 1 (CD guest) complex with ferrocene. From induced circular dichroism experiments, three structures were proposed for these adducts as shown in Figure... 

Crystal structure. The crystalline complexes (tt-CsHs) —, —V, —Cr, —Fe, —Co, —Ni, are isomorphous and have a monoclinic form [57]. On rapid cooling of crystalline ferrocene the crystals disintegrate fairly violently to a powder. Studies on the heat capacity of ferrocene have shown that there is a A point transition at 163 9°K the A range is about 125-200 K [58]. 

The structures of the black crystalline benzene solvate C6o-4C6H6, the black charge-transfer complex with bis(ethylenedithio)tetrathiafulvene, [C6o(BEDT-TTF)2], and the black ferrocene adduct [C6o Fe(Cp)2)2] (Fig. 8.7b) ) have also been solved and all feature the packing of Cso clusters. 

A family of cyclopentadiene(Cp)-containing iron-olefin complexes has been pioneered by Jonas [13-15]. The complexes 38-40 (Scheme 7) can be obtained in a large scale from ferrocene 37 under reducing conditions in the presence of suitable coordinating olefins. Complex 38 is a highly air-sensitive, crystalline material, whereas complexes 39 and 40 are more robust due to their cyclooctadiene (cod)... 

Carbazole will react with 1 or 2 mol of ferrocene in hot decalin in the presence of aluminium-aluminium chloride producing crystalline derivatives in which either one or both" of the benzene rings is linked to iron, 25 and 26, respectively. The sandwich compound 25 was deprotonated to 27 with sodamide in liquid ammonia. A chromium carbonyl complex 28... 

Photolysis of the arene complexes in the presence of monodentate ligands, e.g. carbon monoxide, leads to new complexes of the type CpFe(L) whereas in pure aprotic solvents, ferrocene and iron salts are formed Investigation of the photo-lytic reaction of an iron arene complex with excess ethylene oxide in methylene chloride solution (Meier and Rhis ) showed that a crystalline crown ether complex (structure shown in Fig. 9) was obtained in high yield. Only traces of dioxane could be detected. 

Whether the deligation process occurs spontaneously in a thermal reaction or requires photoactivation depends on the donors employed. For example, most EDA complexes of 6/s(arene)iron(II) acceptors with aromatic donors such as anthracene or durene or with ferrocene are thermally stable and can be isolated in crystalline form (see Figure 3) [124]. Photoactivation of these complexes in acetonitrile by the selective irradiation of their charge-transfer absorption bands uniformly results in the deligation of the acceptor moiety (Eq. 36). 

Two papers published in 1991 described the thermal properties of the diester ferrocene derivatives 8 [15] and 9 [16] (Fig. 9-4). Complexes 8 (n = 3, 4, 6, 8) were found to be non-mesomorphic and 8 (n = 10) seemed to give rise to a smectic phase (unidentified) between 85 °C and 88 °C during the second heating cycle. When 9 n = 1) was cooled from the isotropic melt at a rate of 2 °C/min, a liquid crystalline texture was observed (transition temperatures and liquid crystalline range not given) that, according to the authors, was indicative of a smectic phase. The latter was not identified. Derivative 9 n = 10) formed a nematic phase between 78 °C and 79 °C. This mesophase did not reform on cooling from the isotropic melt. 

Ferrocene forms charge-transfer complexes with a number of acceptor molecules (4, 16, 17 21 j 22, 46, 65), of which that with tetracyanoethylene isolated as a green crystalline substance 4.6, 65) is perhaps the best characterized. In view of the electron-donor properties of the metal atom, it has been suggested that its structure might best be represented by XIX, rather than by the more classical formulation XVIII (4 ). 

Chlathrates may, in a way, be regarded as supramolecular adducts in the crystalline state. C ) forms a series of these compounds which in most cases are obtained by simple cocrystallization of their constituents. Known examples are the inclusion compounds with hydrocarbons tike pentane or nonane, etc., but chlathrates of Qo or C70 have also been found with hydroquinone in the presence of benzene. In these cases the fullerene molecules occupy interstitial spaces within the crystal structure of hydroquinone and form donor-acceptor complexes. Further inclusion compounds with fuUerenes are known for ferrocene and other inorganic substances such as sulfur (Sg), white phosphorus (P4) or complexes hke (PhCN)2PdCl2 and PhsPAuCl (also refer to Section 2.5.3). For the complex of > with ferrocene the crystal structure of the first is found with the latter inserted into the given gaps. The whole stracture can only exist because ferrocene is too weak a reducing agent to transform > into Qo. 

Since its discovery, and because of its stability and the wealth of methods for its derivatiza-tion, ferrocene has played an important role in many areas of synthetic and materials chemistry. Thus ferrocene has been incorporated into more complex structures, displaying, e. g., nonlinear optical, liquid crystalline, or ferromagnetic properties [1]. From a stereochemical point of view, however, one of the most important attributes of, e. g., 1,2- or... 

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