From Icosahedral Boron Subhalides to Octahedral Metalloid Aluminum and Gallium Analogues: Quo vadis, Wade's Rules?

In a dead end? The value of applying Wade's rules to neutral and dianionic [Al 12 Cl 12 ] and [Ga 12 Cl 12 ] species is diminishing: According to DFT calculations, [Al 6 (AlCl 2 ) 6 ] clusters with an octahedral (metalloid) {Al 6 } core (right) are energetically favored over icosahedral compounds (left) as is also found for several structurally examined subhalides (e.g. [Al 22 Cl 20 ]). In addition it is not the postulated centered icosahedral isomers of [Al 13 I 12 ] − clusters that constitute the energetic minima, but the metalloid isomers.