Polyhedral Bismuth Polycations Coordinating Gold(I) with Varied Hapticity in a Homoleptic Heavy-Metal Cluster

Shiny black, air-sensitive crystals of [Au(Bi-8)(2)](AlCl4)(5) were obtained from the reaction of AuCl, BiCl3, and bismuth in the ionic liquid [BMIm] Cl center dot 4AlCl(3) (BMIm = 1-n-butyl-3-methylimidazolium) at 180 degrees C. [Au(Bi-8)(2)](AlCl4)(5) crystallizes in the monoclinic space group P2(1)/n. In the heavy-metal cluster [Au(Bi-8)(2)](5+), two square-antiprismatic Bi-8(2+) polycations coordinate the gold(I) atom in eta(2)-and eta(4)-mode, respectively. Quantum chemical calculations demonstrate that both Bi-8(2+) polycations involve skeletal electrons for the donor bonding, which causes a widening of Bi-Bi distances compared with those in free Bi-8(2+).