Cubane structural chemistry

The formation of tetrameric aggregates with a hetero-cubane structure is a structural motif that is observed for several alkylzinc alkoxides in the solid state (Figure 80). In these structures the alkoxy group is -bonded with its oxygen atom to three zinc atoms. The structural elucidation of [MeZnOMe]4 (152) represented the first example of such a structural motif in organozinc alkoxide chemistry . Later, similar structures were observed for alkylzinc alkoxides containing other alkoxy groups (153, = f-... 

Tetranuclear clusters with a cubane structure are common in 3d-metal coordination chemistry. The relative disposition of orbitals from metal and bridging hgands within such structures favour orthogonality between metallic magnetic orbitals and consequently, ferromagnetic interactions leading... 

Of all polyalkyls, the longest known are the Pt(IV) species. The orange complex [Me3Pt( x -I)]4, which has a cubane structure with octahedral platinum, was described by Pope and Peachey in 1907-1909. Some of its reactions (Eqs. 15.15-15.17) illustrate how the chemistry resembles that for... 

Trinuclear Cuboidal and Heterometallic Cubane-Type Iron-Sulfur Clusters New Structural and Reacticity Themes in Chemistry and Biology R. H. Holm... 

In addition to analogs of known C-based structures, transition metals offer novel bonding possibilities having no known precedents in main-group chemistry. As a variation on the cubane-like cage motif of Fig. 4.26(c) built from tetravalent osmium, we can envision construction of the analogous naked metal cage compound Irg... 

A brief historical note on the structure of the iron-sulfur clusters in ferredoxins is relevant. After the first analytical results revealed the presence of (nearly) equimolar iron and acid-labile sulfur, it was clear that the metal center in ferredoxins did not resemble any previously characterized cofactor type. The early proposals for the Fe S center structure were based on a linear chain of iron atoms coordinated by bridging cysteines and inorganic sulfur (Blomstrom et al., 1964 Rabino-witz, 1971). While the later crystallographic analyses of HiPIP, PaFd, and model compounds (Herskovitz et al., 1972) demonstrated the cubane-type structure of the 4Fe 4S cluster, the original proposals have turned out to be somewhat prophetic. Linear chains of sulfide-linked irons are observed in 2Fe 2S ferredoxins and in the high-pH form of aconitase. Cysteines linked to several metal atoms are present in metallothionein. The chemistry of iron-sulfur clusters is rich and varied, and undoubtedly many other surprises await in the future. 

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