Détermination de la structure cristalline du ferrite de baryum Ba2Fe6O11

The crystal structure of dibarium triferrite Ba₂Fe₆O₁₁ has been solved by direct methods, using intensity data collected by means of an automated diffractometer (MoKα radiation) and corrected for absorption. It crystallizes in the orthorhombic space group Pnnm: a = 23.024(10)Å, b = 5.181(3) Å, c = 8.900(4) Å, Z = 4. Program MULTAN was successfully used for locating Ba²⁺ and most of the Fe³⁺ ions. The structure was further refined by conventional Fourier and least-squares methods (full-matrix program) to a final R value of 0.045 for 1448 observed reflections. Fe³⁺ ions occur in both octahedral (FeO mean distance: 2.02 Å) and tetrahedral (FeO mean distance: 1.865 Å) coordination. Two types of Ba²⁺ ions are found, with six and seven neighboring oxygen atoms. The structure consists of sheets of edge-shared FeO₆ octahedra which are connected by means of corner-shared tetrahedra.     

Telluromolybdates of Transition Metals

The simple and double salts of hexamolybdotelluric(VI) acid, M₃[TeMo₆O₂₄] · nH₂O(NH₄)_2xM_3?x[TeMo₆O₂₄] · mH₂O, as well as substitutive telluromolybdates MTeMo_1?yO₄ and additive telluromolybdates MTe⁴⁺MoO₆, where M = Ni, Mn, Zn, Cu have been prepared. The products of the thermal decomposition of the simple salts of hexamolybdotelluric(VI) acid are the respective substitutive telluromolybdates. MoO₃, and occasionally molybdates. MMoO_4. The double salts decomposition involves the total reduction of Te⁶⁺ to Te⁴⁺ and the formation of respective molybdates or additive telluromolybdates and MoO_3. The obtained preparations have been characterized by the chemical and X-ray methods. The substitutive telluromolybdates adopt a wolframitetype structure as the high-pressure modifications of Co, Ni, Mn, and Zn molybdates reported by Young and Schwarz.     

Binary molybdates K4M2+(MoO4)3 (M2+=Mg, Mn, Co) and crystal structure of K4Mn(MoO4)3

Binary molybdates K₄M²⁺ (MoO₄)₃ (M²⁺=Mg, Mn, Co) isostructural to triclinic \ga-K₄Zn(WO₄)₃ were synthesized, and optimal conditions for their spontaneous crystallization were found. It was established by XRPA and DTA that at 530°C the structure of the compound with cobalt undergoes a transition to the orthorhombic structure of K₄Zn(MoO₄)₃. The structure of K₄Mn(MoO₄)₃ was determined from single crystal diffraction data (a=7.613, b=9.955, c=10.156 Å,α=92.28,β=106.66,γ=105.58°, Z=2, space group $P\bar 1$ , R=0.030). In this compound, Mn has a higher coordination number (CN=5+1) than that of Zn inα-K₄Zn(WO₄)₃ (CN=4+1). The main structural feature is pairs of MnO₆ octahedra linked by the bridging MoO₄ tetrahedra into ribbons stretching along the a axis. The structure is compared with related structures of binary molybdates and other members of the alluaudite family.     

Die Kristallstruktur von Kalium-trithiowolframat-chlorid K3(WOS3)Cl

A recently prepared new thiotungstate has been characterized by three-dimensional X-ray structure analysis, to be a double salt, containing K₂WOS₃ and KCl in equimolar proportions: potassium trithiotungstate chloride, K₃(WOS₃)Cl. Space group: Pca2₁ with a = 12.507, b = 6.317, c = 12,371 Å, Z = 4. The compound represents a new structure type with stoichiometry M^I₂XY₄ · M^IZ. Besides isolated tetrahedral WOS₃^2- ions (bond lengths W–O 1.760 Å, W–S 2.208, 2.197, 2.196 Å) the structure contains Cl^? ions octahedrally co-ordinated by K⁺, the K⁺ ions having 5S + 10 + 2Cl as neighbours. The dimensions of the WOS₃^2? ions in this compound show that, as in other transition metal oxo-, thio- and selenoanions, strong π bonding is present, the W–S bonds taking part in the π bond system.     

Crystal structure of Na6[(UO2)3O(OH)3(SeO4)2]2 · 10H2O

The complex Na₆[(UO₂)₃O(OH)₃(SeO₄)₂]₂ · 10H₂O (I) is synthesized and studied by X-ray diffraction. The compound crystallizes in the orthorhombic crystal system with the unit cell parameters: a = 14.2225(7) Å, b = 18.3601(7) Å, c = 16.5406(6) Å, V = 4319.2(3) ų, Z = 4, space group Cmcm, R ₁ = 0.0406. Compound I is found to be a representative of the crystal-chemical group A₃M³M² ₃T³ ₂ (A = UO²⁺ ₂, M³ = O^2?, M² = OH^?, T³ = SeO^2? ₄) of the uranyl complexes; it contains layer uranium-containing groups [(UO₂)₃O(OH)₃(SeO₄)₂]^3?. These layers linked to form a three-dimensional cage through bonds formed by the sodium atoms with the oxygen atoms of the uranyl ions and SeO₄ groups that belong to different layers.     

Synthesis and structure of a binuclear ruthenium 4-chlorobenzamidato complex

The compound Ru₂Cl(4-Cl-C₆H₄CONH)₄ was prepared by reaction of Ru₂Cl(O₂CCH₃)₄ with 4-Cl-C₆H₄CONH₂ at 180°C. Crystals of the composition Ru₂Cl(4-Cl-C₆H₄CONH)₄CH₃OH were obtained by slow diffusion of CH₃OH containing Et₄NCl into a Me₂SO solution of the compound. The structure of the crystalline product, which loses solvent of crystallization on removal from the mother liquor, was solved by X-ray crystallography by mounting a single crystal in a capillary containing the mother liquor. The crystals belong to the space group P1? (triclinic crystal system) with a = 12.731(3) Å, b = 14.389(3) Å, c = 12.604(3) Å, α = 103.41(2)°, β = 106.43(2)°, γ = 64.90(2)°, V = 1988.6(8) ų and Z = 2. There are two half ruthenium dimers linked by a Cl atom and an uncoordinated solvent CH₃OH molecule per asymmetric unit. The ruthenium dimers lie on two centers of inversion at 0, 0, 0 and 1/2, 0, 0. The chloride ions bridge dinuclear cations in the crystal, forming infinite zigzag chains. The average Ru-Ru distance is 2.296[1] Å and each ruthenium atom has a RuClN₂O₂ coordination sphere where the average Ru′-Ru-Cl angle is virtually linear (175.68[6]°). The metal oxidation states in the complex are + 2 and + 3, giving an average value of + 2.5. The arrangement of four bridging 4-Cl-benzamidato ligands is of the 2 : 2 type. The average Ru-N, Ru-O, Ru-Cl distances and Ru(1)-Cl(1)-Ru(2) angle are 2.036[6] Å, 2.044[5] Å, 2.583[2] Å and 117.26(8)°, respectively. The IR spectrum of the compound shows two N-H stretches at 3380 and 3340 cm^?1. The electronic spectrum of the compound in Me₂SO exhibits bands at 558 nm (ε = 340 M^?1 cm^?1), 425 nm (1000) and 320 nm (22,700).     

Systems Tl2MoO4-E(MoO4)2, where E = Zr or Hf, and the crystal structure of Tl8Hf(MoO4)6

Systems Tl₂MoO₄-E(MoO₄)₂ (E = Zr, Hf) are studied using X-ray powder diffraction, DTA, and IR spectroscopy. Compounds Tl₈E(MoO₄)₆ and Tl₂E(MoO₄)₂ are found in these systems. T-x diagrams for the Tl₂MoO₄-Zr(MoO₄)₂ system are designed. Single crystals are grown and structure is solved for Tl₈Hf(MoO₄)₆. The compound crystallizes in a monoclinic structure with the unit cell parameters a = 9.9688(6) Å, b = 18.830(1) Å, c = 7.8488(5) Å, β = 108.538(1)°, Z = 2, space group C2/m. The main structural fragment is a [HfMo₆O₂₄]^8? isle group. Three crystallographically independent types of Tl polyhedra uniformly fill spaces between [HfMo₆O₂₄]^8? fragments to form a three-dimensional framework.     

Zur Kenntnis des Natriumthioferrates(III)

The mixed valency compound Na₃Fe₂S₄, which is also formed in iron-sodium polysulfide melts, is oxidized and hydrated to NaFeS₂·H₂O (x ≈ 2) on air. It is shown by TGA that this hydrate loses the water reversibly between 80–140 °C. A crystal structure model for the water free phase NaFeS₂ is proposed (space group I 222,a=6.25 Å,b=10.83 Å,c=5.40 Å). The formation of NaFeS₂·xH₂O from Na₃Fe₂S₄ and the reversible phase transformation between NaFeS₂·xH₂O and NaFeS₂ are topotactic. Na⁺ ions in NaFeS₂·xH₂O are easily exchanged against K⁺, Rb⁺, Cs⁺, Tl⁺, Ca²⁺, Sr²⁺, and Ba²⁺. The high chemical reactivity of the sodium thioferrates is discussed and their crystal structures are compared with the other alkali metal thioferrate structures.     

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.     

Synthesis and structure determination of MIL-10: A monodimensional metallodiphosphonate formulated MIVO{O3P-CH2-PO3}(NH4)2 (M = Ti,V)

In the view of synthesizing microporous composite compounds, the ternary systems NH₄VO₃: alkyldiphosphonic acid:H₂O were hydrothermally investigated. Using the methylendiphosphonic acid, the mixture corresponding to the molar ratio 1:0.3:500 heated three days at 200 °C, leads to small platelets whose structure was determined by single crystal X-ray diffraction. Their symmetry is orthorhombic (space group Pnma (n° 62)) with lattice parameters: a = 7.3182(1) Å, b = 16.5633(1) Å, c = 7.5225(2) Å, V = 911.83(4) ų, Z = 4. The compound labelled MIL-10, is formulated V^IVO{O₃P-CH₂-PO₃}(NH₄)₂, and shows a monodimensional structure characterized by the presence of polyhedral chains between which ammonium cations are located. The isostructural titanium compound was also hydrothermally synthesized. Its structure was solved from single crystal data; its symmetry is orthorhombic (space group Cmcm (n° 63)) with lattice parameters: a = 16.462(1) Å, b = 7.7671(6) Å, c = 7.2830(6) Å, V = 931.2(1) ų, Z = 4.     

Synthesis and crystal structure of new complex sodium lanthanide phosphate molybdates Na2MIII(MoO4)(PO4)(MIII = Tb, Dy, Ho, Er, Tm, Lu)

New complex sodium lanthanide phosphate molybdates Na₂M^III(MoO₄)(PO₄)(M^III=Tb, Dy, Ho, Er, Tm, Lu) have been synthesized by the ceramic method (T = 600°C, τ = 48 h), and their unit cell parameters have been determined. The structures of Na₂M^III(MoO₄)(PO₄)(M^III = Dy, Ho, Er, Lu) were refined by the Rietveld method. The compounds are isostructural: they are orthorhombic (space group Ibca, Z = 8) and have layered structures. In the structures of phosphate molybdates, chains of M^IIIO₈ polyhedra and MoO₄ tetrahedra are linked by PO₄ tetrahedra to form layers. The MoO ₄ ^2? anions are involved in dipole-dipole interaction. The sodium ions are arranged in the interlayer space. The compounds melt incongruently at 850–870°C.     

Crystal structures of three complexes structurally similar to KTbW(CN)8 · 7H2O

Three complexes that crystallize into structures like KTbW(CN)₈ · 7H₂O (triclinic crystal system, space group P $ \bar 1 $ ) were structurally characterized by X-ray diffraction: KYMo(CN)₈ · 7H₂O, a = 7.6371(5), b = 9.2569(6), c = 14.4976(2) Å, α = 80.782(6)°, β = 87.644(5)°, γ = 77.645(5)°, V = 988.23(11) ų, Z = 2, ρ_calcd = 1.876 g/cm³; KHoW(CN)₈ · 7H₂O, a = 7.5887(4), b = 9.2232(5), c = 14.4479(9) Å, α = 80.709(5)°, β = 87.525(5)°, γ = 77.457(5)°, V = 974.12(10) ų, Z = 2, ρ_calcd = 2.462 g/cm³; KErW(CN)₈ · 7H₂O, a = 7.6180(5), b = 9.2356(6), c = 14.4903(11) Å, α = 80.655(6)°, β = 87.492(6)°, γ = 77.557(6)°, V = 982.29(13) ų, Z = 2, ρ_calcd = 2.449 g/cm³. The coordination polyhedra of the d element atoms [M(CN)₈] (M⁴⁺ = Mo and W) are dodecahedra; the coordination polyhedra of the rare-earth metal atoms [RN₄(OH₂)₄] (R³⁺ = Y, Ho, and Er) are tetragonal antiprisms. Four bridging cyano groups are coordinated to the W/Mo and rare-earth metal atoms through the C and N atoms, respectively, to form a polymeric 3D structure involving potassium atoms. The coordination polymers can be formulated as {[K(H₂O)][R(H₂O)₄][M(CN)₈] · 2H₂O} _n (R³⁺ = Y, M⁴⁺ = Mo; R³⁺ = Ho and Er, M⁴⁺ = W).     

Synthesis and structural characterization of a polar Os(II,III) complex,Os2(fhp)4Cl

The title compound was prepared by prolonged reaction of Os₂(CH₃COO)₄Cl₂ with Hfhp (Hfhp = 6-fluoro-2-hydroxypyridine) in refluxing toluene in the presence of LiCl. The product, Os₂(fhp)₄Cl (1), is a result of ligand displacement with a concomitant core reduction of Os₂⁶⁺ to Os₂⁵⁺. Crystals were grown by slow diffusion of hexane into a dichloromethane solution of 1. Crystallographic data are as follows: tetragonal crystal system, space group I4mm (No. 107), a = b = 11.000(3) Å, c = 13.142(2) Å, V= 1590(1) ų, Z = 2. The molecule possesses crystallographic 4mm symmetry, with the OsOs bonds lying along the four-fold axes. The four fhp ligands are arranged in a polar fashion around the diosmium core, blocking one axial site. The second axial position is occupied by a chloride ion. The principal distances in 1 are: Os(1)Os(2) = 2.341(1) Å, Os(1)N = 2.027(12) Å, Os(2)O = 2.014(5) Å, Os(2)Cl = 2.487(7) Å. The title compound was also investigated by several physical methods. The electrochemistry as determined by cyclic voltammetry revealed two processes: a reversible, one-electron reduction at E_ox = −0.63 V in dichloromethane and an irreversible oxidation at E_ox = +0.95 V in dichloromethane vs Ag-AgCl at room temperature. The electronic spectrum shows strong bands at 413 nm (ε = 4290 M⁻¹ cm⁻¹), 309 nm (ε = 23,560 M⁻¹ cm⁻¹) and at 294 nm (ε = 26,500 M⁻¹ cm⁻¹) as well as shoulders at 334 and 261 nm.     

Synthèse et structures cristallines de Cs3MI4NO3 (M = Zn,Co, Cd): Un exemple de substitution sélective

The compounds Cs₃MX₅ (M is a bivalent metal, and X an halogen) consist of Cs⁺, I⁻, and distorted (MI₄)²⁻ ions. The separate X⁻ ion suggests a possible substitution by another monovalent anion. The new compounds Cs₃MI₄NO₃ (M = Zn, Co, Cd) have been synthesized and characterized by X-ray diffraction. They are orthorhombic Pnma, a = 10.114(4), b = 11.601(5), c = 14.290(9) Å for Cs₃ZnI₄ NO₃; a = 10.078(8), b = 11.621(4), c = 14.262(6) Å for Cs₃CoI₄NO₃; a = 10.177(4), b = 11.784(5), c = 14.336(7) Å for Cs₃CdI₄NO₃; Z = 4. The crystal structures are described. The NO₃ groups surrounded by six Cs⁺ cations occupy the same sites as the separate I⁻ ion in the Cs₃MI₅ compounds.     

Structure de La2Fe2S5 et de La2Fe1.87S5

The compound La₂Fe₂S₅ is orthorhombic. Cell parameters are: a = 3.997(2)Å; b = 16.485(5)Å; c = 11.394(4)Å. Space group is Cmc2₁ (Z = 4. In the cell, chains of polyedra comprised of sulfur atoms tetrahedrally or octahedrally coordinating centrally located iron atoms give a monodimensional character to the structure. This one is refined to R = 0.037. To complete the study of these chains, in the La₂Fe_2?xS₅ system, vacancies are introduced on iron atom sites. The ordered compound, La₂Fe_1.87S₅, having such vacancies, is an orthorhombic superstructure of the stoechiometric compound. Cell parameters are: a = 3.9996(5)Å; b = 49.508(3)Å; c = 11.308(3)Å. Space group is Cmc2₁ and Z = 12. The structure is refined to R = 0.068. Only two iron atom sites have vacancies. One is tetrahedral, the other octahedral. In this last case the chain deformations are the more important. The chain becomes a sort of tunnel made of atoms of sulfur, with in its center the short iron-iron separation of 2.82 Å.     

Synthesis,Crystal Structures,and Magnetic Properties of Three New Iron Complexes Derived from 3,5‐Bis(pyridin‐2‐yl)‐1,2,4‐triazole

Two new iron(III) complexes and one iron(II) complex have been synthesized from the solvothermal reactions of FeCl₃·6H₂O with 3,5‐bis(pyridin‐2‐yl)‐1,2,4‐triazole (Hbpt) in methanol or acetonitrile. KSCN acted as the reducing agent in the synthesis of iron(II) complex of 3 . [FeCl₃(Hbpt)(H₂O)]·H₂O ( 1 ) crystallizes in the triclinic space group with a = 7.475(1), b = 9.468(2), c = 12.309(2) Å, α = 73.880(2), β = 74.746(2), γ = 81.849(2)°, V = 805.2(2) ų, Z = 2. [Fe₂(bpt)₂Cl₄] ( 2 ): orthorhombic space group Pnnm with a = 9.895(2), b = 10.632(2), c = 13.195(2) Å, V = 1388.1(4) ų, Z = 2. [Fe₂(bpt)₂(MeOH)₂Cl₂] ( 3 ): orthorhombic space group Pbca with a = 14.4204(16), b = 9.8737(11), c = 19.792(2) Å, V = 2818.1(5) ų, Z = 4. 1 features the first structurally characterized metal complex of the neutral Hbpt ligand in which the Hbpt ligand adopts an unprecedented zwitterionic form. 2 shows a neutral dinuclear iron(III) complex and the [Fe₂(bpt)₂]⁴⁺ unit is ideally planar. The two iron(III) ions separated by a distance of 4.408(2) Å are doubly triazolate‐bridged. Each dimeric unit is connected with six other dimeric ones via the bifurcated C‐H···Cl hydrogen bonds, these connections extend the dimeric moieties into a three‐dimensional molecular architecture. 3 is a neutral centrosymmetric dinuclear Fe^II complex, in which intermolecular moderate O‐H···N hydrogen bonding interactions between the methanol molecules and 4‐position nitrogen atoms of the triazolato groups extend the dinuclear species into a two‐dimensional supramolecular architecture of (4,4) topology. Magnetic studies indicate there exists an antiferromagnetic spin coupling in Fe^III₂ and Fe^II₂ units via the double triazolate bridges in 2 and 3 .     

Formation laws for scheelite-like triple molybdates LiMLn2(MoO4)4

The size factor is shown to be decisive in the structure formation of triple molybdates LiMLn₂(MoO₄)₄. The LiMLn₂(MoO₄)₄ compounds (where M is a large alkali metal) are formed when 0.48 Å ≤ r _M ⁺ ? r _Ln ³⁺ ≤ 0.60 Å.     

Structural study of Ba11Fe8Ti9O41 by X-ray diffraction

The crystal structure of Ba₁₁Fe₈Ti₉O₄₁ was determined using single crystal and powder X-ray diffraction methods. This new phase crystallizes in the hexagonal space group P6₃/mmc (No 194) (a=5.7506(3) Å, c=61.413(2) Å; Z=2; ρ_calc.=5.75 g cm⁻³) and exhibits a 26-layer structure built from close-packed [O,(Ba,O)] layers with a stacking sequence (chcchchchcchc)₂. Octahedral sites are occupied by a mixture of Fe³⁺ and Ti⁴⁺, with some preferential ordering of the Fe ions, and tetrahedral sites are occupied by Fe³⁺. The magnetic Fe ions were observed to concentrate within four contiguous cp layers around z=1/4 and 3/4. Unusual structural features, including cation disorder associated with unreasonably short cation–cation separations, were observed to occur within these magnetic sections of the structure. Indexed X-ray powder diffraction data for polycrystalline Ba₁₁Fe₈Ti₉O₄₁ are given. Complementary structural studies of this compound using neutron and electron diffraction are underway and will be described elsewhere along with the results of dielectric and magnetic property measurements.     

Structure of bis(hexamethylenetetramine) hexaaquanickel(II)hexafluorotitanate(IV) monohydrate — [Ni(OH2)6][TiF6](Ur)2·H2O

The X-ray diffraction study of a single crystal with the composition NiTiF₆(Ur)₂·7H₂O is performed, where Ur = C₆H₁₂N₄ is an urotropine (hexamethylenetetramine) molecule. The compound crystallizes in the triclinic P-1 space group: a = 8.7220(5) Å, b = 9.1004(5) Å, c = 17.533(1) Å, α = 75.074(1)°, β = 88.530(1)°, γ = 62.558(1)°, Z = 2, d _x = 1.756 g/cm³, μ = 1.228 mm^?1, R = 0.0351. The crystalline compound is ionic. The structural unit consists of [Ni(OH₂)₆]²⁺ and [TiF₆]^2? ions and Ur and H₂O molecules. The structural formula of the compound is [Ni(OH₂)₆][TiF₆](Ur)₂·H₂O. Hydrogen bonds in the compound are studied and analyzed.     

A new refinement of the crystal structure of the inverse weberite Fe2F5(H2O)2

Fe₂F₅(H₂O)₂ is related to the weberite structure, whose space group is not clearly defined. A careful reexamination of the structure confirms and refines the previous results: Fe₂F₅(H₂O)₂ belongs to the space group Imma with cell parameters a = 7.477(1) Å, b = 10.862(2) Å, c = 6.652(1) Å (Z = 4). The structure has been refined from 379 reflections to R = 0.029 (R_w = 0.034). Fe₂F₅(H₂O)₂ must be considered as an antiweberite structure since M²⁺ and M³⁺ positions are inverse of those of the weberite structure.