Die molekularen Cluster [Bi10Au2](EBi3X9)2 (E = As, Bi; X = Cl, Br) – Synthese, Kristallstrukturen, Drillingsbildung und chemische Bindung

Abstract

AbstractThe Molecular Clusters [Bi10Au2](EBi3X9)2 (E = As, Bi; X = Cl, Br) – Synthesis, Crystal Structures, Twinning and Chemical BondingCooling stochiometric mixtures of molten Bi, BiX3, (X = Cl, Br), E (E = As, Bi), and Au yields black crystals of the low‐valent, molecular compounds [Bi10Au2](EBi3X9)2. The molecules consist of an icosahedral [Bi10Au2]6+ cluster enclosed by two (EBi3X9)3− hemi‐spheres connected via Au–E bonds. The discrepancy of the symmetries of the heteroicosahedron (D5d) and the caps (C3v) gives rise to pseudomerohedral twinning. As a consequence of the superposition of three monoclinic unit cells (space group P21/c; e.g. a = 1059.02(5) pm, b = 1528.60(5) pm, c = 1463.55(6) pm, β = 93.69(1)° for E = Bi, X = Br), the diffraction patterns of the crystals simulate trigonal R‐centered cells with lattice parameters of a ≈ 3000 pm and c ≈ 1700 pm. The constitution of the molecules can be rationalized in terms of an uncommon combination of known and new structural motives: The Wade cluster [Bi10]4+ is capped by two Au+ atoms forming the hetero‐icosahedron [Bi10Au2]6+. In the anionic caps (E0BiII3X9)3−, the BiII atoms are in square planar coordination of four halogenide anions and are furthermore bonded to the E atom on the central axis of the molecule. Since the interaction between E and Au can be classified as a donor‐acceptor bond, the [AuI(E0R3)]2− fragment with R = BiIIX2/1X2/2 is a complex analog to cations [AuI(E0R3)]+ with E = P, As, Sb and R = alkyl or aryl.