The Non-Centrosymmetric Crystal Structure of Molybdenum(VI) Oxide Bromide MoO2Br2


  • Dedicated to Professor Wolfgang Kaim on the Occasion of His 60th Birthday


Red, transparent single crystals of molybdenum(VI) dioxide dibromide MoO2Br2 emerged as by-product after thermal analyses of reaction mixtures comprising REBr3 (RE = La or Gd) and MoO3. The structure of this highly water sensitive compound can be described in the non-centrosymmetric monoclinic space group Cc with the lattice constants a = 1522.33(15) pm, b = 390.61(4) pm, c = 771.09(8) pm, β = 104.394(7)° and four formula units per unit cell. Crystallographically unique Mo6+ cations are surrounded by four oxide and twobromide anions in the shape of distorted octahedra withthe two Br ligands situated in trans position to each other. These octahedra are interconnected by the four O2– anions via vertices to form equation image{MoOequation imageBrequation image} layers parallel to the bc plane, whereas the bromide anions remain terminal. These sheets are piled along [100] with the Br anions pointing towards the center of square voids of adjacent layers.