Ga(8)Br(8).6NEt(3): formation and structure of donor-stabilized GaBr. A nanoscaled step on the way to beta-gallium?

Because of their thermodynamic instability, their sophisticated formation, and their high reactivity, only three textbook examples of Al(I)/Ga(I) subhalides have been crystallized so far: Al(4)Br(4), Al(4)I(4), and Ga(8)I(8). Here, we present the formation and structural characterization of molecular Ga(8)Br(8) species. The different structures of Ga(8)I(8) and Ga(8)Br(8) are discussed with regard to their different formation conditions and their different thermodynamic stability based on results from DFT calculations. Structural as well as thermodynamic properties of Ga(8)I(8) and Ga(8)Br(8) are strongly related to the low-temperature modifications beta-Ga and gamma-Ga. Therefore, our fruitful hypothesis about the fundamental relation between structure and energy of a number of metalloid clusters and the corresponding element modifications is now supported by two binary Ga(I)-halide compounds.