Metal boride clusters

This article reviews strategies that we have used to link transition metal boride clusters of types 1 (semi-interstitial boron, M4B cage) and 2 (fully interstitial boron, M5B cage), and addresses some of the problems of competing reactions. 

The application of B NMR spectroscopy has been a routine and important part of our studies of metal boride clusters, The degradation of the Rug-cage results... 

Boron atoms in transition metal clusters Denuding the boron atom of B-H interactions in transition metal boron clusters Transition metal boride clusters at the molecular level Recent advances in the chemistry of carborane metal complexes incorporating d and /block elements The interplay of alkylidyne and carbaborane ligands at metal centres. I. Synthesis of electronically unsaturated mixed-metal complexes. II. Proton-mediated reactions... 

The electrical conductivity of these alloys is metallic i.e., inverse proportional to the temperature between 4 to 300 K and is about 7 x 106 (Qm) 1 at room temperature. The crystal structure determination [7] shows the B atomic arrangement to consist of coplanar 4B clusters (isolated from one another) with three B atoms at the vertices and one B at the center of a triangle as shown in Fig. 5. This isolated 4B atomic arrangement has no precedent either in metal-borides [14] or boron hydrides [15]. 

Incidentally, the B6 octahedron (Longuet and Roberts, 1955) and B12 cuboocta-hedron (Lipscomb and Britton, 1960) are also found to be two-electron deficient. This electron deficiency of the clusters leads to dramatically different physical properties for trivalent and divalent metal borides as illustrated for example in the next section on the dodecaborides. More on the bonding requirements in the higher borides will be discussed in later sections. 

The second example comes from solid-state chemistry, and the coimection with cluster chemistry is less obvious. Despite this, it is an excellent example of how E/M variation can lead to systematic variation in structure and, consequently, to properties. Although the example is taken from solid-state metal borides, the silicides see Silicon Inorganic Chemistry) and phosphides (see Phosphides Solid-state Chemistry) could have been used. 

Ghosh, S. et al. (2001) Synthesis of [(Cp Re)2BnHn] n=8-10 metal boride particles that stretch the cluster structure paradigms. Angew. Chem. Int. Ed.,... 

Oxides and hydroxides Oxoacids and their salts Compounds containing nitrogen Metal borides Borane and carbaborane clusters... 

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