Cage and cluster structures

Cluster and cage structures are widespread in the chemistry of main group elements, being particularly extensive in the case of boron (Chap. 6). For transition elements the principal... 

Table 1 Cluster and Cage Structures with an Al-N (or Ga-N) Framework...

Penfold, B. R., in Perspectives in Structural Chemistry, Vol. 2, J. D. Dunitz and J. A. Ibers, eds., Wiley, 1968 (encyclopedic review of metal-atom cluster and cage structures). 

Among organotin carboxylates, clusters and cages are formed mainly in di- and monoorganotin compounds. Among triorganotin carboxylates, the predominant structures are chain and discrete structures, although some macrocycles are also known. ... 

Main group elements form a wide variety of neutral, cationic, and anionic compounds having chain, ring, and cage structures (e.g. Zintl anions). [366] All of these may be useful starting materials to be combined with mono- and polynuclear transition metal moieties to generate molecules with novel and exciting structural features. This alternative type of synthetic approach has been used for the synthesis of all the other derivatives included in Table 3-11. For example, as shown in Scheme 3-12, the reaction of either Se4 or Te4 with such mononuclear metal carbonyls as [Fe(CO)s] and [W(CO)6] can yield cluster compounds... 

As the aluminum atoms in the unit structures of MAO are coordinatively unsaturated, the units join together to form clusters and cages. These have molecular weights from 1,200 to 1,600 (as measured by cryoscopy in benzene) and are soluble in hydrocarbons, especially in aromatic solvents. A probably association of two and a cage structure of four [ALtOsMes] units are shown in Figs. 3 and 4. 

The class of nanomaterials that maybe termed zero-dimensional comprise systems that are confined within up to several hundreds of nanometers in aU three dimensions. Although there exists no clear-cut size threshold at which a system switches from a zero-dimensional system to bulk, there is a rather weU-defined class of systems that fit the above definition with unique and intriguing properties. The most commonly studied zero-dimensional systems are quantum dots, nanoparticles (or clusters), and cage-like structures. In this section, we shall begin with an overview of methods used to study such materials. 

Such hydrophobic H-bonding naturally leads to an appreciable reduction in volume, and is therefore increasingly favored at higher pressures. Similarly, in the spirit of LeChatelier s principle, one may expect that the presence of a hydrophobic solute promotes formation of cage structures, i.e., tends to shift the cluster... 

Reduction of the pentaalkyl-1,5-dicarba-closo-pentaboranes(5) 44 with elemental K opens the cluster and subsequent reaction with I2 enforces oxidative fusion of two C2B3 units to give a C4B6 cage (Scheme 3.2-36). The peralkylated hexaboraadamantane derivatives 70 (R = Me, Et X-ray structure analysis for R = Me [89]) rearrange irreversibly into the carboranes 71 with a wido-C4B6 framework [89] (X-ray structural analysis for R = Et [90]). The structure of the nido-C Bf, cluster is fluxional in solution [91]. 

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