The crystal structure of a complex cerium(III) molybdate containing a dimolybdate chain,Ce2(MoO4)2(Mo2O7)

Ce₂(MoO₄)₂(Mo₂O₇) crystallizes in the triclinic system with unit cell dimensions (from single-crystal data) a = 11.903(8), b = 7.509(5), c = 7.385(5) Å, α = 94.33(8), β = 97.41(8), γ = 88.56(7)°, and space group $\text{P}\text{1}\text{, z = 2}$. The structure was solved using Patterson (“P1 method”) and Fourier techniques. Of the 8065 unique reflections measured by counter techniques, 6314 with I ≥ 3σ(I) were used in the least-squares refinement of the model to a conventional R of 0.035 (R_w = 0.034). The structure of Ce₂(MoO₄)₂(Mo₂O₇) consists of dimolybdate chains of the K₂Mo₂O₇ and (NH₄)₂Mo₂O₇ type separated by isolated MoO₄ tetrahedra and cerium(III) polyhedra.     

The crystal structure of a complex cerium(III) molybdate; Ce6(MoO4)8(Mo2O7)

Ce₆Mo₁₀O₃₉ crystallizes in the triclinic system with unit-cell dimensions (from single-crystal data) a = 10.148(5), Å, b = 18.764(6), Å, c = 9.566(5), Å, α = 103.12(7)°, β = 78.07(7)°, γ = 107.69(7)°, and space group $\text{P}\text{1}\text{, z = 2}$. The structure was solved using direct methods with 3113 countermeasured reflections (MoKα radiation), and refined using Fourier and least-squares techniques to a conventional R of 0.039 (ωR = 0.047). Ce₆Mo₁₀O₃₉ has a structure that consists of isolated MoO₄ tetrahedra together with one corner-shared pair of tetrahedra, linked to irregular eight-coordinate Ce(III) polyhedra. The average MoO distance of 1.77 Å, and average CeO distance of 2.52 Å are in good agreement with previously reported values.     

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).     

Structural studies in the Li2MoO4MoO3 system: Part 1 the low temperature form of lithium tetramolybdate,LLi2Mo4O13

LLi₂Mo₄o₁₃ crystallizes in the triclinic system with unit-cell dimensions a = 8.578 Å, b = 11.450 Å, c = 8.225 Å, α = 109.24°, β = 96.04°, γ = 95.95° and space group $\text{P}\text{1}\text{, Z = 3}$. The calculated and measured densities are 4.02 g/cm³ and 4.1 g/cm³ respectively. The structure was solved using three-dimensional Patterson and Fourier techniques. Of the 2468 unique reflections collected by counter methods, 1813 with I ? 3σ(I) were used in the least-squares refinement of the model to a conventional R of 0.031 (ωR = 0.038). LLi₂Mo₄O₁₃ is a derivative of the V₆O₁₃ structure with oxygen ions arranged in a face-centred cubic type array with octahedrally coordinated molybdenum and lithium ions ordered into layers.     

Synthesis and crystal chemistry of NH3(MoO3)3

NH₃(MoO₃)₃ crystallizes with hexagonal symmetry, space group $\text{P6}{}_3\text{m}$, lattice constants a = 10.568 Å, c = 3.726 Å, and Z = 2. The crystal structure has been determined by Patterson synthesis and refined assuming isotropic temperature factors to a final conventional R value of 0.085. The structure shows a three-dimensional arrangement built up of double chains of distorted MoO₆ octahedra, parallel to the [001] direction. The octahedral double chains are linked among each other through common oxygen atoms. In addition to the shared oxygen atoms, each molybdenum is coordinated to one terminal oxygen. MoO distances range from 1.645 to 2.378 Å and OMoO angles from 74.3 to 114.3°. These results are consistent with the fact that molybdenum in high-valence states shows octahedral coordination with terminal oxygens.     

The crystal structure of a sodium molybdenum oxide,Na6Mo10O33, containing cross-linked chains of octahedra and square pyramids

Na₆Mo₁₀O₃₃ crystallizes in the triclinic system with unit-cell dimensions a = 8.049(4), b = 12.180(6), c = 7.576(4) Å, α = 99.96(9), β = 100.74(1), γ = 109.88(10)°, and space group $\text{P}\text{1}$ with z = 1. The structure was solved using Patterson and Fourier methods. Of the 3045 unique reflections measured by counter techniques 2758 with I ≥ 3σ(I) were used in the least-squares refinement of the model to a conventional R of 0.030 (R_w = 0.034). The structure of Na₆Mo₁₀O₃₃ consists of two different types of chains of molybdenum-oxygen polyhedra linked to one another approximately at right angles. One chain of edge- and corner-shared distorted MoO₆ octahedra is approximately parallel to [001] and the second chain, consisting of corner-shared pairs of octahedra edge-shared to pairs of edge-shared MoO₅ square pyramids (inverted with respect to one another), is approximately parallel to [100]. These linked chains form an infinite three-dimensional network in the interstices of which the sodium atoms are located. One of the chains of the Na₆Mo₁₀O₃₃ structure is the same as that found in Ag₆Mo₁₀O₃₃; the second chain, however, does not occur in Ag₆Mo₁₀O₃₃.     

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.     

Etude structurale de combinaisons sulfurees et seleniees du molybdene. II. Structure cristalline de Ni0,33Mo3Se4

The crystals of Ni_0,33Mo₃Se₄, are triclinic, space group $\text{P}\text{1}$, with two formula units in a cell: a = 6,727 (9) Å, b = 6,582 (11) Å, c = 6,751 (6) Å, α = 90.61° (10), β = 92.17° (10), γ = 90.98° (12.) The structure was solved by analogy with Mo₃Se₄ and refined by a full-matrix least squares program to R = 0,093 for 822 independent reflexions. The channels present in Mo₃Se₄ are occupied by Ni so that Ni_0,33Mo₃Se₄ is always a metallic compound.     

Crystal growth and X-ray data of the lead phosphates Pb4P2O9 and Pb8P2O13

Single crystals of the title compounds have been grown by the Czochralski technique. Pb₄P₂O₉ crystallizes in the space group $\text{P2}{}_1\text{c}$ with the parameters a = 9.4812 Å, b = 7.1303 Å, c = 14.390 Å, β = 104.51° and Pb₈P₂O₁₃ in $\text{C2}\text{m}$ with a = 10.641 Å, b = 10.206Å c = 14.342 Å, β = 98.34°.     

Crystal structures of phosphomolybdyl salts: Pb(MoO2)2(PO4)2 and Ba(MoO2)2(PO4)2

Crystal structures of Pb(MoO₂)₂(PO₄)₂ and Ba(MoO₂)₂(PO₄)₂ were determined. Both compounds contain the molybdyl group MoO₂. The monoclinic unit-cell parameters are a = 6.353(7), b = 12.289(4), c = 11.800 Å, β = 92°56(6), and Z = 4 for the lead salt and a = 6.383(8), b = 7.142(7), c = 9.953(8) Å, β = 95°46(8), and Z = 2 for the barium salt. $\text{P2}{}_1\text{c}$ is the common space group. The R values are respectively R = 0.027 and R = 0.031 for 1964 and 1714 independent reflections. The frameworks built up by a three-dimensional network of monophosphate PO₄ and molybdyl MoO₂ groups are similar, characterized mainly by corner-sharing PO₄ and MoO₆ polyhedra. Two oxygen atoms of each MoO₆ group are bonded to the molybdenum atom only as in other molybdyl salts.     

Oxysulfure de scandium Sc2O2S

Sc₂O₂S is hexagonal, $\text{P6}{}_3\text{mmc}\text{, a = 3.5196(4)}$ Å, c = 12.519(2) Å, Z = 2, Dc = 3.807 g cm^?3, Dm = 4.014 g cm^?3, μ(MoKα) = 55.51 cm^?1. The final R value is 0.038 for 205 symmetry-independent reflections. This scandium oxysulfide has c = 12.52 Å, twice the value found in rare earth oxysulfides. An La₂O₂S cell combined with its reflection in a (001) mirror gives the Sc₂O₂S cell.     

Electrochemical crystal growth in the cesium molybdate-molybdenum trioxide system

A systematic investigation of crystal growth in the cesium molybdate/molybdenum trioxide system is described. A previously unknown blue cesium molybdenum bronze phase has been prepared as well as the known red bronze, Cs_0.33MoO₃, and high-quality crystals of the Magneli-phase compound, γ-Mo₄O₁₁. This new blue bronze, with empirical formula, Cs_0.19MoO_2.85, is monoclinic with cell constants, a = 19.198(4) Å, b = 5.519(2) Å, c = 12.213(2) Å, and β = 119.44(2)°. Measurements of the susceptibility and of the resistivity vs temperature are reported. As is the case for other alkali molybdenum bronzes, the product formed is determined by the molar ratio of alkali molybdate to molybdenum trioxide and the melt temperature.     

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.     

The compound Cr2TiO5 in the system Cr2O3TiO2

The compound Cr₂TiO₅ could be synthesized as a stoichiometric single phase above 1660°C in air. Application of selected area electron diffraction, high resolution electron microscopy and powder X-ray diffraction studies showed that Cr₂TiO₅ is isomorphous with CrFeTiO₅, with V₃O₅ type structure. It is monoclinic, a = 7.020(1)Å, b = 5.025(1)Å, c = 9.945(2)Å and β = 111.43(2)°. It was found that Cr₂TiO₅ is unstable relative to a mixture of Cr₂O₃ (ss) and a so-called “E” phase, below 1660°C.     

Some reduced ternary and quaternary oxides of molybdenum. A family of compounds with strong metal-metal bonds

Several new, reduced ternary and quaternary oxides of molybdenum are reported, each containing molybdenum in an average oxidation state <4.0. All are prepared by reactions between a molybdate salt; metal oxide, if needed; and MoO₂ sealed in Mo tubes held at 1100°C for ca. 7 days. Refinement of the substructure of the new compound Ba_0.62Mo₄O₆ was based on an orthorhombic cell, witha = 9.509(2), b = 9.825(2), c = 2.853(1)Å, Z = 2 in space groupPbam; weak supercell reflections indicate the true structure hasc = 8(2.853) Å. The chief structural feature is closely related to that of NaMo₄O₆ (C. C. Torardi, R. E. McCarley,J. Amer. Chem. Soc.101, 3963 (1979)), which consists of infinite chains of Mo₆ octahedral clusters fused on opposite edges, bridged on the outer edges by O atoms and crosslinked by MoOMo bonding to create four-sided tunnels in which the Ba²⁺ ions are located. The structure of Ba_1.13Mo₈O₁₆ is triclinic,a = 7.311(1), b = 7.453(1), c = 5.726(1)Å, α = 101.49(2), β = 99.60(2), γ = 89.31(2)°,Z = 1, space groupP1¯. It is a low-symmetry, metal-metal bonded variant of the hollandite structure, in which two different infinite chains, built up from Mo₄O^2?₈ and Mo₄O^0.26?₈ cluster units, respectively, are interlinked via MoOMo bridge bonding to create again four-sided tunnels in which the Ba²⁺ ions reside. Other compounds prepared and characterized by analyses and X-ray powder diffraction data arePb_xMo₄O₆(x ～ 0.6), LiZn₂Mo₃O₈, CaMo₅O₈, K₂Mo₁₂O₁₉, and Na₂Mo₁₂O₁₉.     

The crystal structure of Ba2V2O7

Ba₂V₂O₇ is triclinic with a = 13.571(3), b = 7.320(2), c = 7.306(2) Å, α = 90.09(1), β = 99.48(1), β = 99.48(1), γ = 87.32(1)°, V = 7.15.1 ų, Z = 4, and space group $\text{P}\text{1}$. The crystal structure was solved by Patterson and Fourier methods and refined by full-matrix least-squares analysis to a R_w of 0.034 (R = 0.034) using 2484 reflections measured on a Syntex $\text{P}\text{1}$ automatic four-circle diffractometer. The structure has two unique divanadate groups that are repeated by the b and c lattice translations to form sheets of divanadate groups parallel to (100). These sheets are linked by four unique Ba atoms that lie between these sheets. Ba(1) and Ba(3) are coordinated by eight oxygens arranged in a distorted biaugmented triangular prism and a distorted cubic antiprism, respectively. Ba(2) is coordinated by 10 oxygens arranged in a distorted gyroelongated square dipyramid and Ba(4) is coordinated by nine oxygens arranged in a distorted triaugmented triangular prism. These coordination numbers are substantiated by a bond strength analysis of the structure, and the variation in 〈BaO〉 distances is compatible with the assigned cation and anion coordination numbers. Both divanadate groups are in the eclipsed configuraton with 〈VO(br)〉 bond lengths of 1.821(4) and 1.824(4) Å and VO(br)V angles of 125.6(3) and 123.7(3)°, respectively. Examination of the divanadate groups in a series of structures allows certain generalizations to be made. Longer 〈VO(br)〉 bond lengths are generally associated with smaller VO(br)V angles. When VO(br)V < 140°, the divanadate group is generally in an eclipsed configuration; when VO(br)V > 140°, the divanadate group is generally in a staggered configuration. Nontetrahedral cations with large coordination numbers require more oxygens with which to bond, and hence O(br) is more likely to be three coordinate, with the divanadate group in the eclipsed configuration. In the eclipsed configuration, decrease in VO(br)V promotes bonding between O(br) and nontetrahedral cations, and hence smaller nontetrahedral cations are generally associated with smaller VO(br)V angles.     

La6Mo8O33: a new ordered defect scheelite superstructure

The structure of La₆Mo₈O₃₃ has been determined from a triple pattern powder diffraction analysis. Two high-resolution neutron diffraction patterns collected at 1.594 and 2.398 Å and one X-rays were used. This molybdate crystallizes in a non-centrosymmetric monoclinic space group P2₁(N°4), Z=2,a=10.7411(3) Å, b=11.9678(3) Å, c=11.7722(3) Å, β=116.062 (1)°. La₆Mo₈O₃₃ is an unusual ordered defect Scheelite. Hence, it should be described with cation vacancies and an extra oxygen atom following the formula: La₆□₂Mo₈O₃₂₊₁. This extra oxygen atom leads to a pyramidal environment, whereas the other molybdenum atoms present tetrahedral environment. A molybdenum tetrahedral is connecting to the pyramid, forming an [Mo₂O₉] unit.     

Crystal structure of Fe2P2O7

Fe₂P₂O₇ crystallizes in the $\text{C}\text{1}$ space group with lattice parameters a = 6.649(2)Å, b = 8.484(2)Å, c = 4.488(1)Å, α = 90.04°, β = 103.89(3)°, γ = 92.82(3)°, and ?_cal = 3.86 g/cc. It is essentially isostructural with β-Zn₂P₂O₇. As in the Zn compound, the bridging oxygen atom in the P₂O₇ group shows a high anisotropic thermal motion. It appears that the P-O-P bond angle is linear as a result of extensive π bonding with the p orbitals on the bridging oxygen atom. The high thermal motion is vibration of the atom into cavities in the structure.