Bi4RuBr2 und Bi4RuI2: Zwei Varianten einer Kolumnarstruktur mit flächenverknüpften quadratischen [RuBi8/2]-Antiprismen

Bi₄RuBr₂ and Bi₄RuI₂: Two Varieties of a Column Structure with Face-Sharing RuBi_8/2] Square Antiprisms Reaction of the elements yields black, lustrous, air insensitive crystals of the subhalides Bi₄RuI₂ (tetragonal, I4/m, a = 1183.9(2) pm, c = 669.7(2) pm, V = 938.66 · 10⁶ pm³) and Bi₄RuBr₂ (monoclinic, I112/m, a = 1211.9(2) pm, b = 1072.6(2) pm, c = 663.9(2) pm, γ = 91.63(1)°, V = 862.64 · 10⁶ pm³). The structures of the homöotypic compounds contain RuBi_8/2] strands of face-sharing square antiprisms. Halogen atoms lie above the edges of alternate Bi₄ squares. Thereby chemical bonding differs significantly within the two types of Bi₄ squares. Though the Ru atoms on the central axis of the strand of antiprisms form pairs, extended Hückel calculations give no evidence of Ru? Ru bonds.