Gallium cluster

A. Schnepf, H. Schnockel, Metalloid aluminium and gallium clusters element modifications on a molecular scale Angew. Chem. Int. Ed. 41 (2002) 3532. 

From AIX/GaX Monohalide Molecules to Metalloid Aluminum and Gallium Clusters... 

This short description of the various elementary modifications of gallium shows its high structural variety, which also includes structural elements that are atypical for metals. This variety is also reflected in the inner composition of the metalloid gallium clusters, as discussed below. 

The Gag[C(SiMe3)3]6 8 cluster, which occurs as an intermediate during the formation of the Gai 9 cluster (see above), includes the most extraordinary arrangement of gallium atoms in the cluster core of all structures of metalloid gallium clusters... 

The more molecular character of 9 in comparison to 8-gallium is responsible for a decrease of the bond lengths by about 25 pm. These results prove that 9, considering its synthesis as well as the electronic structure, has to be classified in between polyhedral gallium clusters such as the square antiprismatic cluster GajjiCnHcih2- 72 and metalloid clusters. 

The compound [Gai9 C(SiMe3)3 6F[Li2Br(THF)6]+ contains 11, the smallest metalloid gallium cluster with a shell-like structure discussed here. The gallium core of 11 contains 19 gallium atoms, 6 of which are connected to a trisyl ligand... 

As already mentioned, 16 is the largest metalloid gallium cluster structurally analyzed so far. In addition to the 84 gallium atoms, the cluster consists of 20 N(SiMe3)2 ligands. Thus, the number of ligands is identical to that found for the... 

Very few examples of these species have appeared since the field was last reviewed.1 One species of interest is the seven-membered heterocycle 100, which was obtained from the dilithiated species 97 via the formation of a Ge=B doubly bonded intermediate (Scheme 30).206 A rare example of a germanium/gallium cluster complex has also been prepared (Equation (162)).207... 

Electron counting in these supraicosahedral gallium clusters consisits of ambiguities since it is not clear which of the bare vertex atoms of the core polyhedra provide the usual three internal orbitals and which vertex atoms provide four internal orbitals. Typically the Wade-Mingos [16-18] or the Jemmis [32, 33] skeletal electron rule is obeyed if about half of the bare vertex gallium atoms use all four orbitals of their sp3 manifolds as internal orbitals, and thus are donors of three skeletal electrons, and the other half of the bare vertex gallium atoms use only three orbitals of their sp3 manifolds and thus are donors of only a single skeletal electron each. 

The reduction of di(neopentyl)gallium chloride with lithium naphthalide was reported to afford the gallium clusters (Ga-CH2CMe3) , but their structures are hitherto unknown. It was assumed that different species with up to 12 gallium... 

Metalloid Gallium Clusters GanRm< and Related Indium Clusters 2.3.4.2.1 The Modifications of Elemental Ga... 

The lack of a single ordering principle is a shortcoming particularly for the gallium clusters, since there are a larger number of them compared with the corresponding aluminum clusters as a result of their improved synthesis procedures (cf. Section 2.3.3). A purely formal means of classification for the gallium clusters... 

Ca- 9 cluster The cluster Ga R,- [R = C(SiMe3)3] 78 (Figure 2.3-24) in this instance is remarkable for many reasons [2] (1) it is the only metalloid gallium cluster for which a 71Ga NMR spectrum in solution has been obtained [2] (2) it is a centered cluster in which the central gallium atom has the same coordination number 12 as in real metals [2] and (3) it is the only metalloid gallium cluster... 

Overall, the metalloid aluminium and gallium clusters bear some relationship to fragments of the bulk metals, protected and stabilised by the ligands on the surface, and as such can be considered intermediate between molecules and metals. They show a marked sensitivity to preparative conditions and the steric influence of the ligands on the surface. Spectroscopic studies and theoretical calculations on the clusters are not discussed here but are summarised in recent review articles, and these additional studies provide a... 

H. Schnockel and A. Schnepf, Nanostructural Element Modifications Synthesis and Structure of Elementoid Gallium Clusters, in Group 13 Chemistry. From Fundamentals to Applications , ACS Symposium Series 822, eds. P. J. Shapiro and D. A. Atwood, American Chemical Society, Washington, DC, 2002, p. 154. 

Quantum Chemical Studies at Gallium Clusters Ga4R4... 

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