MoO<Subscript>3 − δ</Subscript> nanorods

Oxygen-deficient molybdenum trioxide nanorods of composition MoO_2.987 (orthorhombic, a = 3.951(2) Å, b = 13.856(1) Å, c = 3.700(1) Å) were synthesized by a hydrothermal process (150–180°C, 30–50 h). MoO_{3 ? δ} particles were 60–90 nm in diameter; their lengths were several micrometers. X-ray photoelectron and IR spectra of these nanorods were studied, The nanorods had weak paramagnetism, signifying the existence of molybdenum(V) ions in their structure.     

Phase equilibrium in the Cs2MoO4-Bi2(MoO4)3-Zn(MoO4)2 system and the crystal structure of new triple molybdate Cs5BiZr(MoO4)6

The subsolidus region of the Cs₂MoO₄-Bi₂(MoO₄)₃-Zr(MoO₄) system was studied by X-ray powder diffraction. Quasi-binary sections were elucidated, and triangulation performed. Triple molybdates with the component ratios 5: 1: 2 (S ₁) and 2: 1: 4 (S ₂) were prepared for the first time. Crystals of cesium bismuth zirconium molybdate of the 5: 1: 2 stoichiometry (Cs₅BiZr(MoO₄)₆) were grown from fluxed melts with spontaneous nucleation. The composition and crystal structure of this triple molybdate were refined using X-ray diffraction data (collected on X8 APEX automated diffractometer, MoK _α radiation, 2348 F(hkl), R = 0.0226). The trigonal unit cell parameters were as follows: a = b = 10.9569(2), c = 39.804(4) Å, V = 4138.4(4) ų, Z = 6, space group R $ \bar 3 The subsolidus region of the Cs₂MoO₄-Bi₂(MoO₄)₃-Zr(MoO₄) system was studied by X-ray powder diffraction. Quasi-binary sections were elucidated, and triangulation performed. Triple molybdates with the component ratios 5: 1: 2 (S ₁) and 2: 1: 4 (S ₂) were prepared for the first time. Crystals of cesium bismuth zirconium molybdate of the 5: 1: 2 stoichiometry (Cs₅BiZr(MoO₄)₆) were grown from fluxed melts with spontaneous nucleation. The composition and crystal structure of this triple molybdate were refined using X-ray diffraction data (collected on X8 APEX automated diffractometer, MoK _α radiation, 2348 F(hkl), R = 0.0226). The trigonal unit cell parameters were as follows: a = b = 10.9569(2), c = 39.804(4) ?, V = 4138.4(4) ?³, Z = 6, space group R c. The mixed-metal three-dimensional framework in this structure is built of Mo tetrahedra and two sorts of (Bi,Zr)O₆ octahedra. Large interstices accommodate two sorts of cesium atoms. The Bi³⁺ and Zr⁴⁺ cation distributions over two positions were refined during structure solution. Original Russian Text ? B.G. Bazarov, T.V. Namsaraeva, R.F. Klevtsova, A.G. Anshits, T.A. Vereshchagina, R.V. Kurbatov, L.A. Glinskaya, K.N. Fedorov, Zh.G. Bazarova, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 9, pp. 1585–1589.     

Crystal growth and electrical properties of lithium,rubidium, and cesium molybdenum oxide bronzes

Crystals of Li_0.33 MoO₃ (blue), Rb_0.23MoO₃ (blue) and Cs_0.31MoO₃ (red) were grown by electrolysis from MoO₃M₂MoO₄ melts (M =alkali metal) with composition 70–77 mole% MoO₃. Melts richer in M₂MoO₄ produced MoO₂ only. Correlation is made between bronze formation and the coordination of Mo in the melt and in the equilibrium solid phase M₂Mo₄O₁₃. Li_0.33MoO₃ and Cs_0.31MoO₃ are semiconductors with high-temperature-range activation energies 0.16 and 0.12 eV. Rb_0.23MoO₃ has an electrical behavior similar to that of blue K_xMoO₃ with a semiconductor-metal transition at (170 ± 5) K. ESR spectra observed in Li_0.33MoO₃ and Rb_0.23MoO₃ single crystals at 4.2 K show extensive delocalization of the 4d¹ electron associated with Mo(V) centers. Attempts to grow molybdenum bronzes containing Ca or Y were unsuccessful.     

Phase equilibria in the systems Rb2MoO4-R2(MoO4)3-Hf(MoO4)2 (R = Al, In, Sc, Fe(III)) and the crystal structure of double molybdate RbFe(MoO4)2

The systems Rb₂MoO₄-R₂(MoO₄)₃-Hf(MoO₄)₂ have been investigated in the subsolidus region by X-ray powder diffraction, DTA, and IR spectroscopy. Triple molybdates of the composition 5: 1: 2 are formed in the systems with R = Al, In, Sc, and Fe. Molybdates of composition 5: 1: 3 and 1: 1: 1 are found in the iron(III)-containing system in addition to the 5: 1: 2 molybdate. Single crystals of the double molybdate RbFe(MoO₄)₂, which is formed in the Rb₂MoO₄-Fe₂(MoO₄)₃ system, have been grown. The structure of this double molybdate has been refined using X-ray diffraction data (X8 APEX automated diffractometer, MoK _α radiation, 373 F(hkl), R = 0.0287). The trigonal unit cell parameters are the following: a = b = 5.6655(2) Å, c = 7.5061(4) Å, V = 208.65(1) ų, Z = 1, ρ_calc = 3.670 g/cm³, space group R3m1. The structure is formed by layers of FeO₆ octahedra sharing corners with MoO₄ tetrahedra and RbO₁₂ icosahedra.     

Structure determination of low-dimensional conductor sodium molybdenum purple bronze Na0.9Mo6O17

Structure determination of the molybdenum purple bronze Na_0.9Mo₆O₁₇ is carried out by single-crystal X-ray diffraction. The crystal is monoclinic with space group A2 and the lattice constants are a = 12.983(2), b = 5.518(1), c = 9.591(2) Å, β = 89.94(1)°, Z = 2. Full-matrix least-squares refinement gives the final values of R(F) = 0.028 and R_w(F) = 0.040 for 1484 independent reflections, in which the occupancy factor of the sodium atom becomes 0.899(12). The present structure is built up of the linkage of the MoO₄ and MoO₆ polyhedra. There are slabs which consist of four layers of distorted MoO₆ octahedra sharing corners. Both the structure and the molybdenum valence distribution estimated from the MoO bond lengths are considered to lead to the two-dimensional electronic transport. This structure is compared with those of other members of molybdenum purple bronzes, K_0.9Mo₆O₁₇ and Li_0.9Mo₆O₁₇. The difference of the electronic properties among these compounds can be well understood on the basis of their structural characteristics.     

Structure and thermal decomposition of Cs<Subscript>2</Subscript>HPO<Subscript>4</Subscript> · 2H<Subscript>2</Subscript>O

The thermal transformations of disubstituted cesium orthophosphate crystal hydrate under heating in air up to 400°C have been studied. The dehydration process occurs in two stages with the loss of 0.6 water molecules at 60?100°C and 1.4 water molecules at 100?160°C. Anhydrous Cs₂HPO₄ is stable up to 300°C and is completely converted into cesium pyrophosphate Cs₄P₂O₇ at 330°C. The structure of Cs₂HPO₄ · 2H₂O has been determined. The compound crystallizes in monoclinic space group P2₁/c and has the unit cell parameters a = 7.4761(5) Å, b = 14.2125(8) Å, c = 7.9603(6) Å, β = 116.914(5)°, V = 754.20(9) ų, and Z = 4 at?123°C. An earlier unknown polymorph of Cs₄P₂O₇ has been found. According to X-ray powder diffraction data, hexagonal space group Р6₃ has been proposed for the formed pyrophosphate.     

Polychalcogenoaurates(I) with pseudo-onedimensional structures: Preparation and crystal structure of Cs2Au2Se3

Cs₂Au₂Se₃ was obtained as red platelike crystals by reacting a stoichiometric mixture of Cs₂Se, Au and Se at 670K. It crystallizes in space group C2/c, Z = 4 with a = 9.769(5) Å, b = 13.44(1) Å, c = 7.178(3) Å, β = 90.69(1)°. The crystal structure was determined from single crystal data and refined to a conventional R of 0.042 for 674 Fo's and 34 variables. The characteristic structural feature of this new selenoaurate is the formation of infinite helical anionic chains, _∞¹-[AuSeAuSe₂]²⁻ which run parallel to [001] and are separated by the alkali cations. The average Au-Se bond length is 2.402 Å, the bond length in the Se₂-unit is 2.436 Å. Au…Au contacts of 3.200 Å, are formed within the anionic chains. The cesium atoms are coordinated to seven Se in an irregular configuration.     

Hydrothermal synthesis of potassium molybdenum oxide bronzes: structure-inheriting solid-state route to blue bronze and dissolution/deposition route to red bronze

The hydrothermal syntheses of the alkali metal molybdenum bronzes from starting solids (H_xMoO₃) with structural affinities to the desired products were investigated. Single-phase potassium blue and red bronzes were prepared by the hydrothermal treatments at around 430 K, and characterized by powder X-ray diffraction, IR spectroscopy, and SEM. The formation processes of these two bronzes during the hydrothermal treatments were found to differ. The blue bronze was formed by a structure-inheriting solid-state route from H_xMoO₃ with x<0.3, whereas the red bronze was formed for x>0.3 through a solution dissolution/deposition route via the formation of MoO₃+MoO₂.     

Crystal structure and magnetic properties of a Cs3Nb2I9 bioctahedral complex

A cluster complex Cs₃Nb₂I₉ is obtained by a high-temperature reaction of niobium, iodine, and cesium iodide. Its crystal structure is determined: trigonal space group P6₃/mmc, a = 8.2463(3) Å, c = 19.5419(14) Å, V = 1150.84(10) ų, R(F) = 0.0614. The compound obtained is characterized by temperature independent paramagnetism in the temperature range 70–290 K.     

First Mixed Alkaline Uranyl Molybdates: Synthesis and Crystal Structures of CsNa3[(UO2)4O4(Mo2O8)] and Cs2Na8[(UO2)8O8(Mo5O20)]

Two new mixed alkaline uranyl molybdates CsNa₃[(UO₂)₄O₄Mo₂O₈] ( 1 ) and Cs₂Na₈[(UO₂)₈O₈(Mo₅O₂₀)] ( 2 ) have been obtained by high‐temperature solid state reactions. Their crystal structures have been solved by direct methods: Compound 1 : triclinic, P , a = 6.46(1), b = 6.90(1), c = 11.381(2) Å, α = 84.3(1), β = 91.91(1), γ = 80.23(1)°, V = 488.6(2) ų, R₁ = 0.06 for 2865 unique reflections with |F_o| ≥ 4σ_F; Compound 2 : orthorhombic, Ibam, a = 6.8460(2), b = 23.3855(7), c = 12.3373(3) Å, V = 1975.2(1) ų, R₁ = 0.049 for 2120 unique reflections with |F_o| ≥ 4σ_F. The structure of 1 contains complex sheets of UrO₅ pentagonal bipyramids and molybdenum polyhedra. The sheets have [(UO₂)₂O₂(MoO₅)] composition. Natrium and cesium atoms are located in the interlayer space. Cesium atoms are situated between the molybdenum clusters, whereas natrium atoms are segregated between the uranyl complexes. The large Cs⁺ ions are localized between the Mo₂O₉ groups and force the molybdenum polyhedra to rotate relative to the [(UO₂)₂O₂(MoO₅)] sheets. Such rotation is impossible for U⁶⁺ polyhedra due to their rigid edge‐sharing complexes. The distance between the U⁶⁺ polyhedra vertices of neighboring layers is 3.8 Å, that allows the Na⁺ ion to be positioned between the uranyl groups. The crystal structure of 2 is based upon a framework consisting of [(UO₂)₂O₂(MoO₅)] sheets parallel to (010). The sheets are linked into a 3‐D framework by sharing vertices with the Mo(2)O₄ tetrahedra, located between the sheets. Each MoO₄ tetrahedron shares two of its corners with two MoO₆ octahedra in the sheet above, and the other two with MoO₆ octahedra of the sheet below. Thus four MoO₆ octahedra and one MoO₄ tetrahedron form chains of composition Mo₅O₁₈. The resulting framework has a system of channels occupied by the Cs⁺ and Na⁺ ions.     

K4MoV8P12O52, a tunnel structure characterized by an unusual valence of molybdenum

A new phosphate of molybdenum (V) K₄Mo^v₈P₁₂O₅₂ has been isolated and its structure solved from a single crystal X-ray diffraction study. It crystallizes in a monoclinic cell, space groupC2–c, with the parametersa = 10.7433(16)Å,b = 14.0839(9)Å,c = 8.8519(7)Å, and β = 126.42(1)°. After refinement of the different parameters, the reliability factors were lowered toR = 0.026 and_w = 0.029. The framework “Mo₈P₁₂O₅₂” can be described as corner-sharing PO₄ tetrahedra,P₂O₇groups, and MoO₆ octahedra. Although the “O₆” octahedron surrounding the molybdenum ion is almost regular, the metal ion is strongly off center so that its coordination is better described as a MoO₅ pyramid. This particular coordination, which characterizes Mo(V), is discussed.     

Homogeneity regions of double molybdates in the Na2MoO4-MgMoO4 system and structures of triclinic Na1.51Mg2.245(MoO4)3 and Na1.66Mn2.17(MoO4)3

In the samples of the Na₂MoO₄-MgMoO₄ system quenched in the air at above 600°C, by powder X-ray diffraction two double molybdates of variable composition are detected: monoclinic alluaudite-like Na_4?2x Mg_1+x (MoO₄)₃ (0.05 ≤ x ≤ 0.35) and triclinic Na_2?2y Mg_2+y (MoO₄)₃ (0.10 ≤ y ≤ 0.40) isostructural to previously studied Na₂Mg₅(MoO₄)₆. Sodium-magnesium molybdate of the Li₃Fe(MoO₄)₃ structure type is not revealed in this system. By spontaneous flux crystallization, the crystals are obtained and the structures of two triclinic double molybdates of the Na₂Mg₅(MoO₄)₆ structure type (space group $P\bar 1$ , Z = 1) containing magnesium and manganese are determined. The results of the refinement of site occupancies made it possible to determine the composition of the studied crystals: for the compound with magnesium (Na)_0.5(Na_0.255□_0.745)(Na_0.755Mg_0.245)Mg₂(MoO₄)₃ or Na_1.51Mg_2.245(MoO₄)₃ (a = 6.9577(1) Å, b = 8.6330(2) Å, c = 10.2571(2) Å, α = 106.933(1)°, β = 104.864(1)°, γ = 103.453(1)°, R = 0.0188); for the compound with manganese (Na)_0.5(Na_0.33□_0.67)(Na_0.83Mn_0.17)Mn₂(MoO₄)₃ or Na_1.64Mn_2.17(MoO₄)₃ (a = 7.0778(2) Å, b = 8.8115(2) Å, c = 10.4256(2) Å, α = 106.521(1)°, β = 105.639(3)°, Γ = 103.233(1)°, R = 0.0175). The Na₂Mg₅(MoO₄)₆ structure is redetermined and it is shown that actually it corresponds to the composition Na_1.40Mg_2.30(MoO₄)₃.     

Crystal structure and some thermodynamic characteristics of cesium silicate Cs6Si10O23

Crystals of cesium silicate Cs₆Si₁₀O₂₃ were prepared upon the crystallization of glass Cs₂O · 4SiO₂. The crystal structure of Cs₆Si₁₀O₂₃ was determined by single-crystal X-ray diffraction (space group P $\bar 6$ 2m, a = 9.578(5) Å, c = 4.155(5) Å, Z = 0.5, 269 F(hkl), R = 0.0424). The three-dimensional tetrahedral silicate framework in Cs₆Si₁₀O₂₃ is similar to that in Rb₆Si₁₀O₂₃ (space group P $\bar 6$ 2m, a = 9.475(5) Å, c = 8.200(5) Å) in which layers formed by 12-membered rings of silicon-oxygen tetrahedra may be distinguished. However, while in the rubidium silicate structure the vertices of the tetrahedra neighboring in a layer point to opposite directions, in cesium silicate these tetrahedra are disordered as regards the arrangement of vertices either upward or downward relative to the layer plane. The random disorder results in a smaller unit cell parameter c in Cs₆Si₁₀O₂₃ compared to Rb₆Si₁₀O₂₃. The compound melts congruently; the melting temperature and the enthalpy of melting of the crystal are 1208 ± 1 K and 156.2 ± 15 kJ/mol, respectively.     

Synthesis and crystal structure of Cs3ZnBr5

The compound Cs₃ZnBr₅ was synthesized from cesium and zinc bromides. The single crystals were grown by the Bridgman method. The structure of Cs₃ZnBr₅ was studied. The compound crystallizes in the tetragonal system with the unit cell parameters: a = b = 9.633(2) Å, c = 15.141(5) Å, V = 1404.8(6) ų, Z = 4, space group I4/mcm; ρ_calcd = 4.083 g/cm³, ρ_exp = 4.074 ± 0.001 g/cm³. The compound Cs₃ZnBr₅ is not hygroscopic and congruently melts at 530°C; it is transparent at 2.5 to 25 μm. The refractive indices are N _p = 1.682, N _g = 1.686. The microhardness is 560 MPa.     

Synthese und Struktur eines Caesiumoxonitridomonowolframates(VI), Cs7[WN1,5O2,5]2

Synthesis and Crystal Structure of a Cesium Oxo Nitrido Monotungstate(VI), Cs₇[WN_1.5O_2.5]₂ Mixtures of tungsten powder and WO₃ react with an excess of CsNH₂ in autoclaves at 650 °C to yield hygroscopic yellow crystals of cesium oxo nitrido tungstate(VI) Cs₇[WN_1.5O_2.5]₂ besides Cs₆[W₂N₄O₃] [1]. After the reaction the crystals are embedded in cesium metal (from thermal decomposition of CsNH₂), which was washed out by liquid ammonia. The crystals allowed a successful X‐ray structure determination. Cs₇[WN_1.5O_2.5]₂ crystallizes in the space group P2₁/c with the lattice parameters a = 6.766(1) Å, b = 11.205(3) Å, c = 22.299(4) Å, β = 91.05(1)° and Z = 4. The crystal structure is built up by isolated tetrahedra [WX₄] with X = N, O, which are separeted by cesium cations.     

Hochdrucksynthese von Caesiumamidazid,Cs2(NH2)N3 aus Caesiummetall und Ammoniak

High-pressure Synthesis of Cesium Amide Azide, Cs₂(NH₂)N₃ from Cesium Metal and Ammonia The reaction of cesium and yttrium metal with ammonia at 5–6 kbar and 190–220°C led to a well crystallized cesium amide azide and to YN. The formation of the cesium compound is discussed by volume effects. X-ray investigations gave the atomic arrangement of the compound. The tetragonal unit cell with a = 8.194(3) and c = 4.450(1) Å contains two formula units. The structure determination was successfull in the space group P4/mbm. The azide ion has different coordination and bond length (1.255 Å) as compared with that in the alkali metal azides (1.17 Å). The amide ions carry out a strong libration.     

Synthesis of reduced complex oxides of molybdenum by fused salt electrolysis

Fused salt electrolysis has been used to prepare a number of reduced oxides of molybdenum with lanthanum, neodymium, and yttrium in single crystal or oriented polycrystalline form. The average valence of molybdenum in the various compounds ranged from 5.67 to 3.50. Previously unreported compounds include La₅Mo₄O₁₆ (triclinica = 5.64 Å,b = 20.7 0Å,c = 5.64 Å, α = 86.55°, β = 90.0°, γ = 93.45°); La₂Mo₂O₇ (orthorhombic,a = 12.19 Å,b = 6.05 Å,c = 3.87 Å); LaMo₂O₅ (hexagonal,a = 8.378 Å,c = 19.26 Å). In addition, single crystal specimens have been prepared of Y₂MoO₅,Ln₅Mo₃O₁₆(Ln =La, Nd) and metal atom cluster compounds of theA₂Mo₃O₈ type (A = Mg, Co, Ni, Zn).     

Ba0.15WO3: A bronze with an original pentagonal tunnel structure

The structure of a new barium tungsten bronze, Ba_0.15WO₃, has been established by X-ray diffraction and high-resolution microscopy studies. This bronze is orthorhombic, space group Pbm2 or Pbmm, with a = 8.859(3) Å, b = 10.039(8) Å, and c = 3.808(2)Å. The “WO₃” framework is built up from corner-sharing WO₆ octahedra forming pentagonal tunnels where the barium ions are located. Structural relationships with hexagonal tungsten bronze and tetragonal tungsten bronze structures are discussed.