Ligand-free clusters

Exercise 2.7. A Zintl ion with the formula [TlSnci]3- has been synthesized and characterized. Suggest a structure. 

Answer. A count of 42 eve or 11 sep yields n= 10 so a bicapped square antipris-matic c/oso-cluster shape is predicted and was found in a solid-state structure determination. 

A facility with the use of multicenter bond models is very helpful in thinking about problems of this type. Insight into new structure types arises more rapidly 

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The Wade rules can be applied to ligand-free cluster compounds of main-group elements. If we postulate one lone electron pair pointing outwards on each of the n atoms, then g — 2n electrons remain for the polyhedron skeleton (g = total number of valence elec-... 

Contrary to this chemical cluster growth is the formation of naked, ligand free clusters in a more physical sense. Considering the cluster growth in Fig. 8 and 9, it is to be recognized that both five-fold symmetry and hexagonal (hep) or cubic (ccp) structures are realized. While in smaller clusters the icosahedral and cuboctahedral symmetry are... 

Roy et al. investigated the influence of ligands on structural and electronic properties of InP nanoparticles. As ligands they have considered both H and CH3 and observed a large suppression of In to P electron transfer compared to ligand free cluster. They showed that HOMO-LUMO gap depends critically on the type and number of ligands that are added. 

Goellner, J. F., Neyman, K. M., Mayer, M., Nortemann, F., Gates, B. C., and Rosch, N., Ligand-free osmium clusters supported on MgO. A density functional study. Langmuir 16, 2736 (2000). 

NMR studies of solutions of inter-metallic phases led to recognition of the potential use of polyatomic Zintl ions as reagents for the generation of new cluster compounds (Eichhorn et al., 1988). Examples of transition-metal derivatives have been discussed in Chapter 5 and the structures of the ions themselves were used as examples of ligand-free main-group clusters in Chapter 2 (Corbett, 1985 Fassler, 2001). The following examples illustrate recent developments in the chemistry of these clusters derived from solid-state syntheses. 

The formation of full-shell clusters is a consequence of their thermodynamic stability. The ideal shape of such particles makes them unusually stable species with respect to chemical reactions. Thus, ligand-free AU55 clusters cannot be oxidized... 

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