Synthesis and characterization of an Al-69(3-) cluster with 51 naked Al atoms: Analogies and differences to the previously characterized Al-77(2-) cluster

A disproportionation process of a metastable AlCl solution with a simultane ous ligand exchange-Cl is substituted by N(SiMe3)(2)-leads to a [Al-69{N(Si Me3)(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-r ay crystal structural analysis. Regarding its structure and the packing wit hin the crystal, this metalloid cluster with 4 times more Al atoms than lig ands is compared to the [Al77N(SiMe3)(2)}(20)](2-) cluster that has been pu blished 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 anal ysis shows significant differences in topology and distance proportions. Th e differences between these-at a first glance almost identical-Al clusters demonstrate that results of physical measuring, e.g., of nanostructured sur faces which carry supposedly identical cluster species, have to be interpre ted with great caution.