Aluminum subhalides of the type Al(22)X(20).12L (X = Cl, Br; L = THF, THP) are the only known representatives of polyhedral aluminum subhalides and exhibit interesting multicenter bonding properties. Herein, we report on the synthesis and structural investigation of the first chlorides of this type. Additional investigations applying solid-state (27)Al NMR (MAS), XPS (of Al(4)Cp(4) and Al(22)X(20).12L), and quantum chemical calculations shed more light upon the structure of the molecules and possible Al modifications.

The novel neutral gallium cluster compounds [Ga18R*8] (1) and [Ga22R*8] (2) are obtained by warming up a metastable solution of gallium(I) bromide in THF/C6H5CH3 after addition of equimolar amounts of supersilyl sodium NaR* from -78 degrees C to room temperature (R* = SitBu3 = supersilyl). From X-ray structure analyses, the observed arrangements of the 18 and 22 Ga atoms in 1 and 2, respectively, are comparable with an 18 atom section of the beta-Ga modification, or show at least some kind of relationship to a 22 atom section of the Ga-III modification. This allows a description of both the clusters as metalloid. The topology of the atoms in 2 is also well explained by the Wade-Mingos rules as an eightfold capped closo-Ga14 cluster, whereby the Ga atoms of Ga14 occupy the center and the corners of a cuboctahedron with one Ga3 face replaced by a Ga4 face. Some concepts are presented about the formation mechanism, the cluster growth, and the metalloid character of the two Ga cluster compounds.

A disproportionation process of a metastable AlCl solution with a simultaneous ligand exchange-Cl is substituted by N(SiMe(3))(2)-leads to a [Al(69)[N(SiMe(3))(2)](18)](3-) cluster compound that can be regarded as an intermediate on the way to bulk metal formation. The cluster was characterized by an X-ray crystal structural analysis. Regarding its structure and the packing within the crystal, this metalloid cluster with 4 times more Al atoms than ligands is compared to the [Al(77)N(SiMe(3))(2)](20)](2-) cluster that has been published four years ago. Although there is a similar packing density of the Al atoms in both clusters as well as in Al metal, the X-ray structural analysis shows significant differences in topology and distance proportions. The differences between these-at a first glance almost identical-Al clusters demonstrate that results of physical measuring, e.g., of nanostructured surfaces which carry supposedly identical cluster species, have to be interpreted with great caution.

A doubly capped In(6) octahedron characterizes the structure of the dark green octaindane (tBu(3)Si)(6)In(8) (see picture), which is obtained from (C(5)Me(5))In and tBu(3)SiNa in pentane at -78 degrees C. In1/In1' are the capping atoms, and In2/In2' form the apexes of the stretched In(6) octahedron. Thus, in agreement with the results of ab initio calculations, the compound can be classified as a hypoprecloso-indane.

Dedicated to Professor Heinrich Vahrenkamp on the occasion of his 60th birthdaySolutions of metastable aluminum(i) halides [1] can be prepared by condensation of the high-temperature molecules AlX (X Cl, Br, I) with suitable donor-containing solvents. The thermodynamically favored disproportionation of these compounds to aluminum metal and the trihalide can be controlled kinetically by the choice of halide, donor, and temperature. Thus, with NEt 3 as donor a planar Al 4 species (for example, Al 4 Br 4´4 NEt 3[2] ) is obtained, whereas with THF the polyhedral subhalide Al 12 (AlBr 2´T HF) 10´2 THF forms as a result of ªinternalº disproportionation. [3] An additional variation of the disproportionation is acheived by replacement of the halide with suitable bulky substituents. Use of the N(SiMe 3 ) 2 group proved to be especially successful: Reaction of LiN(SiMe 3 ) 2 with a solution of AlI provided a Al 77 R 20 2À compound with the largest metalloid cluster yet characterized by diffraction methods. This compound can be viewed as an intermediate on the way Heys, D. G.