Polybismuthide Anions as Ligands: The Homoleptic Complex [(Bi7)Cd(Bi7)]4- and the Ternary Cluster [(Bi6)Zn3(TlBi5)]4-

We present the results from a reactivity study of the binary anion (TlBi3)(2-) towards Group 12 metal compounds MPh2 (M=Zn, Cd, Hg) to gain access to coordination compounds of polycyclic polypnictide molecules such as Bi-7(3-) or Bi-11(3-). The coordination chemistry of these polybismuthide cages has been unprecedented to date, while it has been known for a long time for the lighter Group 15 anions Pn(7)(3-) (Pn=P, As, Sb). The use of (TlBi3)(2-), previously shown to release Tl under certain conditions in situ, resulted in the formation of the first heterometallic polyanion in which a nortricyclane-type polybismuthide coordinates a transition-metal atom, [(Bi-7)Cd(Bi-7)](4-). Reactions with the lighter Group 12 metal precursor yielded the uncommon ternary cluster [(Bi-6)Zn-3(TlBi5)](4-), most likely representing a reaction intermediate, and at the same time hinting at the formation of the nortricyclane-shaped cage. Quantum-chemical studies provide deeper insight into the stability trends of the [(E-7)M(E-7)](4-) anion family and reveal a complex bonding situation in [(Bi-6)Zn-3(TlBi5)](4-), which features both localized and multi-center bonding.