Metalloid Neutral and Anionic Clusters E Rm

Since the large majority of metalloid clusters E R n. is observed for the two elements A1 and Ga, this section is divided in two parts, including the few clusters for In hitherto known. For many of the metalloid clusters discussed in this section (for a definition of metalloid cf. Section 2.3.1, Introduction) the technique of cryochemistry is essential, i.e., trapping of a high-temperature species together with an excess of a suitable solvent in order to obtain a metastable solution. Detailed descriptions and discussions of this technique have been presented recently [7-12], 

The next step in the direction of a deeper understanding of nanostructured materials depends on being able to isolate the individual structurally determined cluster units from the crystal lattice and then determine the physical properties of the single clusters in question. This long-term objective has been partially achieved in the gas phase investigation of a structurally determined Gai9R6 cluster [R = C(SiMe3)3] in an FT mass spectrometer (cf. Section 2.3.4.2.5, Ga clusters) 

Reactions in which substitution is favored tend to the formation of oligomeric AIR species [e.g., (AlCp )4] 9, whereas, when substitution is strongly hindered, the formation of aluminum metal through disproportionation of the AlX species is observed. 

The principle and the significance of metalloid clusters for the understanding of the formation of metals are made clear by the two largest A1 clusters 61 and 63, which have almost the same size as the 69 and 77 A1 atoms and 18 and 20 N(SiMe3) groups [3, 91]. In both cases the A1 atoms are arranged in shells (Fig- 

All previously discussed metalloid A1 clusters show that the favored arrangement of A1 atoms is a close packing as in the metal, whereby the observed distortions reflect the adaptation of the cluster core to the (A1R) corset . Since the packing 

---