Metastable Aluminum(I) halide solutions proved to have a high potential for the synthesis of novel subvalent Al compounds, such as AlnXm species (X=Cl, Br, I; nm, average oxidation state of Al below +1) or AlnRm species (R=bulky ligand; n>m). There are two principal reaction types, which are essential for the formation of the compounds discussed herein. The disproportionation, which finally results in Al(III) halides and Al metal and the metathesis which leads to a substitution of X atoms against R groups. By this way the metalloid cluster compounds [Al7{N(SiMe3)2}6]−, [Al12{N(SiMe3)2}8]−, [Al14I6{N(SiMe3)2}6]2−, [Al69{N(SiMe3)2}18]3−, and [Al77{N(SiMe3)2}20]2− could be isolated. The characteristic feature of these metalloid Al clusters is the number of AlAl contacts being larger than the number of Alligand bonds, i.e. there are more ‘naked’ than ligand-bonded Al atoms. Furthermore, the topology of the closest packing in Al metal is already pre-formed in these 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 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.

An intermediate on the pathway from AlI species to aluminum metal: This is one way to view the [Al14{N(SiMe3)2}6I6]2− cluster (structure shown) formed from the reaction of an aluminum(I) iodide solution with LiN(SiMe3)2. With the help of density functional calculations it was confirmed that the observed metalloid structure is more favorable for the Al14 cluster than a polyhedral structure that follows Wade's rules.

Als ein Intermediat auf dem Weg von AlI-Spezies zum Aluminiummetall kann der bei der Umsetzung von AlI-Iodid-Lösung mit LiN(SiMe3)2 entstehende [Al14{N(SiMe3)2}6I6]2−-Cluster (Struktur siehe Bild) angesehen werden. Mit Hilfe von Dichtefunktionaltheorie-Rechnungen wird bestätigt, dass die beobachtete metalloide Struktur für den Al14-Cluster günstiger ist als eine polyedrische Struktur mit Wade-Bindungsverhältnissen.

Numerous crystal structures of donor-stabilized LiX species are known, but only two of them show a heterocubane arrangement [LiX(Do)]4 (X = Cl, Br; Do = donor) in the solid state. Herein we report the X-ray crystal structure of [LiI(NEt3)]4 (1), obtained by the reaction of LiN(SiMe3)2 with either GaI or All in the presence of NEt3. The structural backbone of 1 is a [LiI]4 heterocubane core, which is compared to [LiX]4 (X = Cl, Br) as well as to [Li(CH3)]4. The energetics of the formation of 1 and its stability with respect to solid LiI is rationalized and additionally supported by DFT (density functional theory) calculations.