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

Abstract

Red, transparent single crystals of molybdenum(VI) dioxide dibromide MoO 2 Br 2 emerged as by-product after thermal analyses of reaction mixtures comprising REBr 3 (RE = La or Gd) and MoO 3 . 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 Mo 6+ cations are surrounded by four oxide and two * Dr. I. Hartenbach

Frustrated Dipole Order Induces Noncollinear Proper Ferrielectricity in Two Dimensions

“…In this dioxydihalides family, WO 2 Cl 2 and MoO 2 Br 2 have been synthesized experimentally [27][28][29], while the crystal structures of the corresponding fluorides, iodides, and CrO 2 X 2 are isomeric or unknown. Thus, in the following only WO 2 Cl 2 and MoO 2 Br 2 will be studied using density functional theory (DFT) [26].…”

“…As shown in Fig. 1(g), each M O 2 X 2 layer is composed of corner-sharing octahedra [29]. Contrary to most 2D materials which display compact honeycomb or triangular atomic arrangements, the "square" lattice of M O 2 X 2 is spatially loose, which is advantageous for polar distortions.…”

“…9) and P 2 1 am (No. 26), respectively [27,29]. The optimal distances (d 0 's) between adjacent layers are shorter in the α phases (see Table S1 in SM [26]), which are lower in energy than the β phases by 70 meV/W and 77 meV/Mo.…”

Seven Up: The Incorporation of Li+ Cations in Yttrium Tungstate and Silicate Tungstate

“…Synthesis of LiY 5 [SiO 4 ] 2 [WO 4 ] 4 : In order to synthesize yttrium fluoride oxidotungstate(VI) YF[WO 4 ], by attempts to recrystallize the reaction mixture of yttrium sesquioxide (Y 2 O 3 : 99.9 %, ChemPur, Karlsruhe, Germany), yttrium trifluoride (YF 3 : 99.9 %, ChemPur, Karlsruhe, Germany), and tungsten trioxide (WO 3 : 99.9 %, Merck, Darmstadt, Germany) with a molar ratio of 1:1:3 in evacuated and sealed silica ampoules using lithium chloride (LiCl: 99.9 %, ChemPur, Karlsruhe, Germany) as fluxing agent at 900 °C colorless, platelet‐shaped single crystals as well as microcrystalline powder of LiY 5 [SiO 4 ] 2 [WO 4 ] 4 besides by‐products of yttrium tungstates were obtained among other, unidentified by‐products. The incorporation of silicate anions into the crystal structure of LiY 5 [SiO 4 ] 2 [WO 4 ] 4 suggests the reaction of fluoride anions with the wall of the silica containers, instead of their incorporation into the crystal structure of the title compound.…”

Mononuclear anionic AO2X3compounds with non-VSEPR structure

“…9 Essentially the same T-4 structure is preserved for CrO 2 Cl 2 in the solid state, 10 whereas for the heavier homologues MoO 2 Cl 2 6 and WO 2 Cl 2 , 11 extended lattices are found, in which the metal centres achieve six-coordinate environments as a result of extended bridging systems (Scheme 1b). § 12,13 The different degrees of intermolecular association observed in the solid state denote different Lewis acidity for the corresponding d 0 metal centres. Accordingly, CrO 2 Cl 2 shows no affinity for any additional Cl − ligand, ¶ 14 while the heavier metals form [MO 2 Cl 3 ] − compounds.…”