Dimorphie von SrTa4O11 - ein Schritt von der tetragonalen Bronzestruktur zur Struktur von CaTa4O11

Dimorphism of SrTa₄O₁₁–a Step from the Tetragonal Structure of Bronzes to the Structure of CaTa₄O₁₁ Hexagonal SrTa₄O₁₁ is a new modification and isostructural with CaTa₄O₁₁. It was obtained by heating the already known SrTa₄O₁₁ in a chlorine atmosphere at 1000–1100°C. The Guinier powder pattern could be indexed with the following hexagonal unit cell: a = 6.25 Å; c = 12.33 Å. In air at 1180°C SrTa₄O₁₁(hex.) changes into the well-known TTB-modification (corresponding to the tetragonal tungsten bronzes). The transition of SrTa₄O₁₁(TTB) to SrTa₄O₁₁(hex.) was only observed in the presence of a transporting agent (Cl₂) or a mineralizer (melt of B₂O₃) at temperatures below 1100°C. This transition could not be achieved by means of a solid state reaction. In a (Ca, Sr) Ta₄O₁₁ solid solution with at least 78 At.-% Ca the hexagonal form could be stabilized even at temperatures where otherwise the TTB-modification occurred.     

Crystallization of ultraphosphates via the gas phase. The crystal structures of FeP4O11, ZnP4O11 and CdP4O11

The new ultraphosphates FeP₄O₁₁, ZnP₄O₁₁ and CdP₄O₁₁ of the CuP₄O₁₁ structure type were synthesized from the corresponding meta- or polyphosphates and P₄O₁₁. Crystallization via the gas phase has been achieved at elevated temperatures using a mixture of P (3 mg) and I₂ (50 mg) as mineralizer. The crystal structure consists of a two-dimensional phosphate network, built from four crystallographically independent 10-membered polyphosphate rings. Each ring contains four secondary and six tertiary PO₄-groups. Two crystallographically independent metal sites showing sixfold coordination by terminal oxygen atoms are located inbetween the phosphate layers. FeO₆-octahedra (2.028(3) Å < d̄ FeO₆ < 2.268(3) Å) and ZnO₆ octahedra (2.002(2) Å < d̄ ZnO₆ < 2.256(2) Å) exhibit slightly larger radial distortion than the CdO₆-octahedra (2.215(7) Å < d̄ CdO₆ < 2.383(3) Å).     

Struktur und Bildung von RbCs11O3

Structure and Formation of RbCs₁₁O₃ Formation, crystal structure, and thermal analysis of the ternary suboxide RbCs₁₁O₃ are reported. RbCs₁₁O₃ crystallizes in the orthorhombic space group Pmn2₁? C (Z = 2) with lattic constants a = 1648.4(4), b = 1371.3(5) c = 913(1) pm. It melts incongruently at +10°C and consists of an (idealized) hexagonal close packed arrangement of Cs₁₁O₃ groups, the single Rb atom occupying the quasi tetrahedral holes of this arrangement. Structural relationships to CsCs₁₁O₃ and Cs₁₁O₃ are discussed.     

Zum Aufbau von RbNa5Be8O11

On RbNa₅Be₈O₁₁ For the first time RbNa₅Be₈O₁₁ was obtained by annealing intimate mixtures of the binary oxides (Rb:Na:Be = 1.1:5.5:8, Ni-cylinder, 650°C, 21d). The compound crystallizes triclinic (P 1 ) with a = 1 063.4 pm, b = 645.6 pm, c = 948.8 pm, α = 110.2º, β = 114.9º, γ = 90.8º, Z = 2. The crystal structure was solved by four-circle-diffractometer data [Siemens AED2, 3099 I₀ (hkl), R = 5.1%, R_w = 3.8%]. The Madelung Part of Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, are calculated.     

Die Netzstruktur von RbNb4Cl11

The Network Structure of RbNb₄Cl₁₁ RbNb₄Cl₁₁ was obtained by solid state reaction of Nb powder, NbCl₅ and RbCl at 575 °C. The structure was examined by powder and single‐crystal X‐ray diffraction. RbNb₄Cl₁₁ crystallizes with the space group Pmma (No. 51), Z = 2 , a = 1621.1(1) pm, b = 690.22(4) pm, c = 657.93(3) pm, R₁ = 0.0257 and wR₂ = 0.0470, being isotypic with CsNb₄Cl₁₁. The structure contains edge bridging and face sharing [NbCl₆] octahedra forming the motif of a wave‐like net. The net‐planes are stacked parallel to the c axis direction. Rubidium ions occupy voids between the net openings of adjacent layers. The electronic properties of Nb₄‐clusters in the structure are being discussed.     

Zur Kenntnis von Ba2As6O11

Concerning Ba₂As₆O₁₁ Ba₂As₆O₁₁ was prepared by hydrothermal reaction of BaO with As₂O₃ at a temperature of 200°C. An X-ray structural analysis demonstrated that the phase contains highly condensed polyarsenate(III) anions (As₆O₁₁^4?)_n. A zweier double chain structure was observed for the anion, in which the individual chains are bridged to one another by two Ψ-AsO₃ tetrahedra, so that As₁₀O₁₀ rings are formed. The double chains are linked into “double sheets”, perpendicular to the b-axis, through relatively strong secondary O … As bonds with an average length of 2.68 Å.     

Mittlere Schwingunsamplituden von SF4O

Mean amplitudes of vibration for SF₄O have been calculated from known spectroscopic data in a wide temperature range. The results are briefly discussed and some comparisons with related species are made.

     

Kristallstruktur von LiHC2O4-H2O

LiHC₂O₄ · H₂O crystallizes in space group P 1 with a₀ = 4.99, b₀ = 6.16, c₀ = 3.45 Å; α₀ = 96.3°, β₀ = 98.0°, γ₀ = 80.4° and Z = 1. The crystal structure has been determined by direct methods. Refinement by least squares methods resulted to R₁ = 8,3%. In the structure the oxalate group is not planar. The angle between the two O? C? O planes is 2.9°.     

Die Kristallstruktur von LiEu3O4

The crystal structure of LiEu₃O₄ which represents a new structure type was solved by usual methods with the aid of integrated WEISSENBERG photographs (MoK_α radiation, 787 reflexions) and refined to a reliability index of 4.3%. In LiEu₃O₄ just as in the first known europium(II, III)-oxide, Eu₃O₄, a clear distinction is possible between the divalent and trivalent europium ions. The given assignment which is based on crystal chemical arguments has been verified indirectly by means of the isostructural compound LiSr₂EuO₄, the cation distribution of which was established experimentally. The structure of LiEu₃O₄ is discussed in connection with the related oxides EuO and Eu₃O₄. The geometrical relations to the latter are of special interest, as LiEu₃O₄ undergoes a topotactical transformation into Eu₃O₄ by heating it in a high vacuum. There is an astonishing close structural relationship between LiEu₃O₄ and Yb₃S₄: except for lithium all the atoms are correlated as for isostructural compounds.     

Zur Verbindungsbildung von MeO:M2O3. VI. Darstellung und Strukturaufklärung von Sr1,33 Pb0,67 Al6O11

Compound Formation MeO: M₂O₃. VI. Synthesis and Structure Determination of Sr_1,33 Pb_0,67 Al₆O₁₁ Single crystal of Sr_1,33Pb_0.67Al₆O₁₁ could be prepared with a PbO flux. (Space group D–Pnnm, a = 22.13, b = 4.88, c = 8.42 Å, Z = 4) Sr²⁺ and Pb²⁺ are statistically intercalated into a framework of AlO₆ octahedra and AlO₄ tetrahedra. The typical coordination of Sr²⁺ and Pb²⁺ is realized by occupying different positions in the same cavern.     

Beiträge zum Koordinationsverhalten von Oxidionen in anorganischen Feststoffen. IV [1] Darstellung,Kristallstruktur und spektroskopische Charakterisierung von NiP4O11 und CaNiP2O7

Synthesis, Crystal Structures, and Spectroscopic Characterization of NiP₄O₁₁ and CaNiP₂O₇ From melts single crystals of NiP₄O₁₁ and CaNiP₂O₇ have been grown. These allowed refinement of the crystal structures (NiP₄O₁₁: C1¯, Z = 8, a = 12, 753(4)Å, b = 12.957(3)Å, c = 10.581(4)Å, α = 89.42(2)°, β = 116.96(2)°, γ = 90.20(2)°, R1 = 0.027, wR2 = 0.072 for 3058 I_o > 2σ (I_o), 3291 independent reflections, 290 parameters; CaNiP₂O₇: P1¯, Z = 2, a = 6.433(3)Å, b = 6.536(4)Å, c = 6.515(2)Å, α = 66.4(2)°, β = 87.5(2)°, γ = 82.7(2)°, R1 = 0.026, wR2 = 0.062 for 1624 I_o > 2σ (I_o), 2189 independent reflections, 101 parameter) and measurement of polarized electronic absorption spectra in the uv/vis/nir region (6000—32000 cm^—1). NiP₄O₁₁ is isotypic to the series of ultraphosphates MP₄O₁₁ (M = Mn, Fe, Co, Cu, Zn, Cd) that exhibit a two‐dimensional network formed from ten‐membered phosphate rings. CaNiP₂O₇ completes the series of diphosphates AMP₂O₇ (A: Ca, Sr, Ba; M = Cr — Zn) and is isotypic to CaCoP₂O₇. Ni²⁺ ions in both phosphates show distorted octahedral coordination. The electronic transitions associated with the chromophores [Ni²⁺O₆] are nicely reproduced by calculations within the framework of the angular overlap model (AOM). The parametrisation scheme leads to e_{σ, norm}(2.0Å) = 3690 cm^—1 and B = 896 cm^—1 (C/B = 4.2) for CaNiP₂O₇ and e_{σ, norm}(2.0Å) = 4150 cm^—1 and B = 948 cm^—1 (C/B = 4.5) for NiP₄O₁₁ (Δ_o(CaNiP₂O₇) = 6800 cm^—1; Δ_o(NiP₄O₁₁) = 7100 cm^—1).     

Darstellung und Struktur von Ag2C4O4

Preparation and Structure of Ag₂C₄O₄ Ag₂C₄O₄ occurs in a yellow and a colourless modification. Both forms decompose to metallic silver upon heating. Ag⁺ is coordinated in two different fashions in the yellow Ag₂C₄O₄. Ag(1) shows distorted tetrahedral coordination, Ag(2) is coordinated in an unusual distorted square planar manner. The connection of Ag⁺ and C₄O₄^2? leads to a complicated three-dimensional framework. C₄O₄^2? is planar with C? O and C? C bonds lengths typical of complete delocalization of the π-electron system.