Cubane crystallization

SbCl3 in pentane at 150° under a pressure of H2/CO gave black crystals of [Sb4 Co(CO)3 4] which was found to have a cubane like structure with Sb and Co at alternate vertices of a grossly distorted cube (Fig. 13.24). ... 

The elucidation of the crystal structures of two high-spin EPR proteins has shown that the proposals for novel Fe-S clusters are not without substance. Two, rather than one novel Fe-S cluster, were shown to be present in nitrogenase, the key enzyme in the biotic fixation of molecular nitrogen 4, 5). Thus the FeMoco-cofactor comprises two metal clusters of composition [4Fe-3S] and [lMo-3Fe-3S] bridged by three inorganic sulfur atoms, and this is some 14 A distant from the P-cluster, which is essentially two [4Fe-4S] cubane moieties sharing a corner. The elucidation of the crystal structure of the Fepr protein (6) provides the second example of a high-spin EPR protein that contains yet another unprecedented Fe-S cluster. 

This supramolecular approach has been used as a way to facilitate the crystallization of cuboidal aqua ions and to capture single intermediates present in complex solution mixtures. For example, [M3Q4Clx(H20)9.x] (Q = S, Se) supramolecular adducts have been isolated for x =1-5 from aqueous HCl solutions by varying the acid concentrations where the aggregates contain in each case only one of all possible isomers [46]. In addition to the hydrogen bonds, other kinds of interactions, namely C1---H20, C1---C1 and Q---Q contacts, are also involved in the network propagation. This supramolecular approach has also been efficiently employed for the crystallization of a large number of aqua complexes within the [M3M Q4] cubane-type family, where M is a transition or post-transition metal [47]. 

It is well-known, that in most carboxylic acid crystal structures, the conformation of the carboxyl group is synplanar and that the most frequent and dominant interlink is the syn-syn centrosymmetric dimer synthon, II. This synthon is found in nearly a third of all crystalline carboxylic acids, with or without any other functionality being present in the molecule, signifying robustness.1211 Against such a background, the crystal structures of 1,4-cubane-... 

Figure 5 shows the crystal structures of 4-chloro, 4-bromo, 4-iodo and 4-carbomethoxy-l-cubane car-... 

R. J. Butcher, A. Bashir-Hashemi, R. Gilardi, Network hydrogen bonding the crystal and molecular structure of cubane-l,35,7-tetracarboxylic acid dihydrate , J. Chem. Cryst., 1997, 27, 99-107. 

Furthennore, resonance Raman studies of aconitase by Johnson et al. (53) demonstrated homologous spectra for both inactive and active aconitase. This suggests similar vibrational modes and thus similar core structures for the two forms. Finally, a cubane structure for the [3Fe-4S] cluster is supported by recent protein crystallographic studies of inactive aconitase by Robbins and Stout (54). (Recent results from Jensen s group (55) on the redetermination of the crystal structure of the Azotobacter ferredoxin I clearly show that the 3Fe cluster does not have a [3Fe-3S] ring structure, as originally determined (37), but has a [3Fe-4S] cubane structure.)... 

In addition, crystal structures of several halomethylzinc alkoxides and an acy-loxymethylzinc reagent have been reported (Figure 2, 7-9). lodo- and chloromethylzinc alkoxides exist as tetramers in cubane or bis(cubane)-like structures. However, these... 

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