Synthesis, Structure, and Bonding of a Molecular Metalloid Ga₁₉ Cluster Anion

A metastable Ga I Br solution, prepared by a co-condensation technique, reacts with LiC(SiMe 3 ) 3 to give the metalloid Ga 19 cluster compound [Ga 19 (C(SiMe 3 ) 3 ) 6 ][Li 2 Br(THF) 6 ] ( 1 ). The central Ga atom of 1 shows a 6 + 6 coordination to the 12 non-ligand-bearing Ga atoms. Due to the high symmetry of the environment of this Ga atom, a sharp 71 Ga NMR signal at δ 71 Ga = −134 was observed in solution. The experimentally found NMR signal of the topologically “metallic” Ga atom is compared to the results of DFT calculations of different Ga 19 R 6 - species as well as to those of the naked Ga 13 - cluster. On these grounds it is shown that the electronic behavior of naked clusters is completely different from that of ligand-stabilized metalloid clusters.