Metal discrete clusters

By incorporation of alkali metal halides in the reaction mix, materials of composition M4-[MfiXig] can be produced in which each MgXn unit has a further six X atoms attached to its apices, so forming discrete clusters. 

The serendipitous discovery of this compound has proven to be extremely important to our visions of possibilities for new metal-metal bonded structures in reduced oxide phases. In retrospect it is amazing that oxide phases containing molybdenum in oxidation states less than 4+ were essentially unknown and certainly structurally uncharacterized. The existence of the previously mentioned series M2 Mo30q and LiM Mo303 should have been a tip-off to an extensive chemistry for metal-metal bonded molybdenum oxide systems. Indeed, subsequent work has revealed a plethora of new compounds all of which (where structure has been determined) feature strong metal-metal bonding in either discrete cluster units or extended chain arrays. 

Notes on cluster phases in triel alloys. Li and Corbett (2004) have shortly reviewed the systematic and extensive experimental and theoretical work carried out by Corbett and co-workers (see for instance Corbett 1996). Considering alkali metal-triel alloys, they underlined, particularly for Ga, In and Tl, the richness of their chemistry (see also 5.3.4.4). Gallium forms many anionic network structures (and only a few phases containing isolated cluster units), indium gives several examples of both network and discrete cluster structures, thallium forms especially discrete clusters (Tl , T157A Tl , Tl , Tl(f, Tl ). 

Figure 4. (b) Overlay of the ligand backbones of 40 metal complexes of the tetradentate ligand shown in (a) (c) averaged ligand structure with metal positions of three discrete clusters (Mn11, Cu1, Cu11).19,75... 

For detailed listings of the many known cluster compounds there are now numerous reviews (12-14). Suffice it to say here, that among the clusters of type (1) formed by rhodium and platinum we now have discrete arrays of thirty, or more, metal atoms and are entering into a fascinating borderline area between metal atom clusters and metals as such. 

II. From Discrete Cluster Molecules to Metal-Metal Bonds in the Solid State. 80... 

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