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1.
Maryvonne Hervieu Bernadette Domengès Bernard Raveau 《Journal of solid state chemistry》1985,58(2):233-242
During the investigation of the phosphate bronzes (PO2)4(WO3)2m [MPTBP] and Kx(P2O4)2WO3)2m [DPTBH] crystals of a new type were observed. HREM images of these crystals showed twinned ReO3-type slabs the junction of which was parallel to the (102)ReO3 plane. The proposed model identified the twin boundary as built from P2O7 groups involving the formation of pentagonal tunnels. The structure of this new type of extended defects is quite original: it corresponds to a new structural type named “diphosphate tungsten bronzes with pentagonal tunnels” [DPTBP], for which no regular member could be synthesized. Image calculations were performed to confirm the junction model. Apart from the disordered stacking of the ReO3-type slabs, very few defects were observed and shear planes were only obtained in reduced samples. This new structural type takes its place in the large family of phosphate tungsten bronzes where all members (DPTBH, MPTBH, MPTBP) are very closely related. 相似文献
2.
The first members of the series AxP4O8(WO3)2m were studied by means of electron microscopy. These bronzes can be classified into two groups on the basis of ReO3-type block composition: even- and odd-m members. High-resolution lattice images of tungstophosphate crystals (m ≤ 10) allow us to establish a correlation between the image contrast and the framework of the structure. The structural mechanism proposed for this series is discussed and compared to the possibility of intergrowth, and to the crystallographic shear phenomena observed in tungsten and molybden oxides. 相似文献
3.
The crystal structure of KxP4W14O50 (x = 1.4) has been solved by three-dimensional single crystal X-ray analysis. The refinement in the cell of symmetry , with a = 6.660(2) Å, b = 5.3483(3) Å, c = 27.06(5) Å, and β = 97.20(2)°, Z = 1, has led to R = 0.036 and Rw = 0.039 for 2436 reflections with . This structure belongs to the structural family KxP4O8(WO3)2m, called monophosphate tungsten bronzes (MPTB), which is characterized by ReO3-type slabs of various widths connected through PO4 single tetrahedra. This bronze corresponds to the member m = 7 of the series and its framework is built up alternately of strands of three and four WO6 octahedra. The structural relationships with the P4O8(WO3)2m series, called M′PTB, are described and the possibility of intergrowth between these two structures is discussed. 相似文献
4.
The crystal structure of KP8W40O136, the tenth member of the series KxP4O8(WO3)2m, has been resolved by three-dimensional single-crystal X-ray analysis. The space group is and the cell parameters are a = 19.589(3) Å, b = 7.5362(4) Å, c = 16.970(3) Å and β = 91.864(14)°. The framework is built up from ReO3-type slabs connected through pyrophosphate groups. The structure is compared to those of the other members of the series: although the ReO3-type slabs show a different type of tilting of the WO6 octahedra, the dispersion of WO distances is always higher for the octahedra linked to one or two P2O7 groups and decreases in proportion as W is farther from these groups. The perovskite cages of the slabs are described and compared to those encountered in the structures of WO3 and of the bronzes AxWO3. 相似文献
5.
A Mo(V) oligophosphate, built up of di and triphosphate groups, Cs(MoO)4(P2O7)2(P3O10) has been synthesized for the first time. This compound crystallizes in the triclinic P−1 space group with , , , α=94.534(6)°, β=102.520(6)°, γ=103.663(4)°. This original structure can be described by the association of MoO6 octahedra, MoP2O11 units built up of one P2O7 group sharing two apices with the same MoO6 octahedron, and triphosphates groups P3O10. The resulting tridimensional framework forms large S-shaped tunnels running along c where the Cs+ cations are located. 相似文献
6.
The actual structure of the vanadium phosphate K6(VO)2(V2O3)2(PO4)4(P2O7) has been determined, using a much larger single crystal than previously used for the isostructural Rb-phase. The actual supercell is four times larger than the corresponding orthorhombic subcell with , , , α=β=γ=90°. The structure resolution, performed in the triclinic space group C-1, shows that the P2O7 groups alone are responsible for the superstructure, all the other atoms keeping the atomic positions of the orthorhombic subcell. This structural study shows a perfect ordering of the P2O7 groups in the actual structure, in contrast to the results obtained from the subcell. Concomitantly, the V4+ and V5+ are found to be ordered in the form of [110] stripes. 相似文献
7.
M. Maczka W. Paraguassu P.T.C. Freire F.E.A. Melo 《Journal of solid state chemistry》2004,177(6):2002-2006
A high-pressure Raman scattering study of the tungstate Al2(WO4)3 is presented. This study showed the onset of two reversible phase transitions at 0.28±0.07 and 2.8±0.1 GPa. The pressure evolution of Raman bands provides strong evidences that both the transitions involve rotations/tilts of nearly rigid tungstate tetrahedra and that the structure of the stable phase in the 0.28-2.8 GPa range may be the same as the structure of the ambient pressure, low-temperature monoclinic (C2h5) ferroelastic phase of Al2(WO4)3. 相似文献
8.
Two new mixed valent Mo(III)/Mo(IV) diphosphates containing lead Pb2(PbO)2Mo8(P2O7)8 and PbK2Mo8(P2O7)8 have been synthesized. The [Mo8P16O56]∞ frameworks of these phosphates are closely related to that of K0.17MoP2O7: the MoO6 octahedra and P2O7 groups form two sorts of large eight-sided tunnels. They are occupied in an ordered way by PbO chains and Pb2+ cations in Pb2(PbO)2Mo8(P2O7)8 and by K+ and Pb2+ cations in PbK2Mo8(P2O7)8. It results in different symmetries of these two structures, which are tetragonal and monoclinic, respectively, showing the great flexibility of these mixed frameworks, susceptible to accommodate various species with different sizes. 相似文献
9.
Evgeny V. Alekseev Sergey V. Krivovichev W. Depmeier H. Katzke Evgeny V. Chuprunov 《Journal of solid state chemistry》2006,179(10):2977-2987
Three new uranyl tungstates, A8[(UO2)4(WO4)4(WO5)2] (A=Rb (1), Cs (2)), and Rb6[(UO2)2O(WO4)4] (3), were prepared by high-temperature solid-state reactions and their structures were solved by direct methods on twinned crystals, refined to R1=0.050, 0.042, and 0.052 for 1, 2, and 3, respectively. Compounds 1 and 2 are isostructural, monoclinic P21/n, (1): a=11.100(7), b=13.161(9), , β=90.033(13)°, , Z=8 and (2): , , , β=89.988(2)°, , Z=8. There are four symmetrically independent U6+ sites that form linear uranyl [O=U=O]2+ cations with rather distorted coordination in their equatorial planes. There are six W positions: W(1) and W(2) have square-pyramidal coordination (WO5), whereas W(3), W(4), W(5), and W(6) are tetrahedrally coordinated. The structures are based upon a novel type of one-dimensional (1D) [(UO2)4(WO4)4(WO5)2]4− chains, consisting of WU4O25 pentamers linked by WO4 tetrahedra and WO5 square pyramids. The chains run parallel to the a-axis and are arranged in modulated pseudo-2D-layers parallel to (0 1 0). The A+ cations are in the interlayer space between adjacent pseudo-layers and provide a 3D integrity of the structures. Compounds 1 and 2 are the first uranyl tungstates with 2/3 of W atoms in tetrahedral coordination. Such a high concentration of low-coordinated W6+ cations is probably responsible for the 1D character of the uranyl tungstate units. The compound 3 is triclinic, P1¯ a=10.188(2), b=13.110(2), , α=97.853(3), β=96.573(3), γ=103.894(3)°, , Z=4. There are four U positions in the structure with a typical coordination of a pentagonal bipyramid that contain uranyl ions, UO22+, as apical axes. Among eight W sites, the W(1), W(2), W(3), W(4), W(5), and W(6) atoms are tetrahedrally coordinated, whereas the W(7) and W(8) cations have distorted fivefold coordination. The structure contains chains of composition [(UO2)2O(WO4)4]6− composed of UO7 pentagonal bipyramids and W polyhedra. The chains involve dimers of UO7 pentagonal bipyramids that share common O atoms. The dimers are linked into chains by sharing corners with WO4 tetrahedra. The chains are parallel to [−101] and are arranged in layers that are parallel to (1 1 1). The Rb+ cations provide linkage of the chains into a 3D structure. The compound 1 has many structural and chemical similarities to its molybdate analog, Rb6[(UO2)2O(MoO4)4]. However, the compounds are not isostructural. Due to the tendency of the W6+ cations to have higher-than-fourfold coordination, part of the W sites adopt distorted fivefold coordination, whereas all Mo atoms in the Mo compound are tetrahedrally coordinated. Distribution of the WO5 configurations along the chain extension does not conform to its ‘typical’ periodicity. As a result, both the chain identity period and the unit-cell volume are doubled in comparison to the Mo analog, which leads to a new structure type. 相似文献
10.
Ivan V. Ogorodnyk Igor V. Zatovsky Vyacheslav N. Baumer 《Journal of solid state chemistry》2006,179(12):3681-3687
The single crystals of caesium magnesium titanium (IV) tri-oxo-tetrakis-diphosphate bis-monophosphate, Cs3.70Mg0.60Ti2.78(TiO)3(P2O7)4(PO4)2, crystallize in sp. gr. P-1 (No. 2) with cell parameters a=6.3245(4), b=9.5470(4), c=15.1892(9) Å, α=72.760(4), β=85.689(5), γ=73.717(4), z=1. The titled compound possesses a three-dimensional tunnel structure built by the corner-sharing of distorted [TiO6] octahedra, [Ti2O11] bioctahedra, [PO4] monophosphate and [P2O7] pyrophosphate groups. The Cs+ cations are located in the tunnels. The partial substitution of Ti positions with Mg atoms is observed. The negative charge of the framework is balanced by Cs cations and Mg atoms leading to pronounced concurrency and orientation disorder in the [P2O7] groups, which coordinate both. 相似文献
11.
采用从头计算MP2和CIS方法分别优化等电子双核d8配合物[Pt2(P2O4H2)4]4-和[Pt2(P2O4CH4)4]4-的基态和激发态结构。结果表明基态Pt-Pt距离分别为0.290 5和0.298 7 nm,与实验的0.292 5和0.298 0 nm符合。NBO计算的Pt-Pt键级以及Pt原子间伸缩振动说明Pt-Pt相互作用具有吸引本质。CIS计算揭示电子激发到Pt-Pt的σ(pz)成键轨道使得相互作用增强。保持激发态几何,含时密度泛函理论(TD-DFT)计算的溶液发射分别为449和475 nm,与实验值512和510 nm接近。 相似文献
12.
Nandini Garg Vinod Panchal Surinder M. Sharma 《Journal of solid state chemistry》2005,178(4):998-1002
The high pressure behavior of aluminum tungstate [Al2(WO4)3] has been investigated up to ∼18 GPa with the help of Raman scattering studies. Our results confirm the recent observations of two reversible phase transitions below 3 GPa. In addition, we find that this compound undergoes two more phase transitions at ∼5.3 and ∼6 GPa before transforming irreversibly to an amorphous phase at ∼14 GPa. 相似文献
13.
用液相反应-前驱物烧结法制备了Cr2(WO4)3和Cr2(MoO4)3粉体。298~1 073 K的原位粉末X射线衍射数据表明Cr2(WO4)3和Cr2(MoO4)3的晶胞体积随温度的升高而增大, 本征线热膨胀系数分别为(1.274±0.003)×10-6 K-1和(1.612±0.003)×10-6 K-1。用热膨胀仪研究了Cr2(WO4)3和Cr2(MoO4)3在静态空气中298~1 073 K范围内热膨胀行为,即开始表现为正热膨胀,随后在相转变点达到最大值,最后表现为负热膨胀,其负热膨胀系数分别为(-7.033±0.014)×10-6 K-1和(-9.282±0.019)×10-6 K-1。 相似文献
14.
Single crystals of the new Bi(III) phosphates, Rb6Bi4(PO4)2(P2O7)3, have been isolated and their structure has been determined by X-ray diffraction techniques. This compound crystallizes in the monoclinic space group P21/c with a=9.077(1)Å, b=9.268(2)Å, c=36.418(6)Å, β=95.75(1)° and Z=8. The crystal structure is made up of BiO5 and BiO6 polyhedra sharing the corners with PO4 tetrahedra and P2O7 diphosphate groups. The structure can be described as infinite anionic layers with composition [Bi4(PO4)2(P2O7)3]∞6− parallel to the [301] plane, connected via P-O-Bi bridges to form a three-dimensional open framework. This framework delimits tunnels running along [100] and [010] directions, where the rubidium ions reside. This compound exhibits a rubidium ion conduction but with rather low conductivity value at 640 K. 相似文献
15.
The mixed-valence oxide P4W10O38, which can be considered as the nonintegral member n = 2.5 of the series P4W4nO12n+8, crystallizes in the monoclinic system with unit-cell dimensions a = 6.5656(25), b = 5.2850(15), c = 20.573(15) Å, β = 96.18(4)°, and space group P21. The crystal structure was solved by conventional Patterson and Fourier techniques using 2339 counter-measured reflections that obeyed the condition I > 3σ(I) and refined to an R factor of 0.074 (Rw = 0.077). Basically, the framework of the structure built up from ReO3-type slabs connected through PO4 tetrahedra looks like that of P4W8O32 previously described. Unlike P4W8O32, two successive ReO3-type slabs have a different width corresponding to two and three WO6 octahedra so that the structure can be considered as an intergrowth of the integral members n = 2 and n = 3 of the series P4W4nO12n+8. 相似文献
16.
The nature of the protonation reaction of (
o(CO)3 (M = Mo, W; R = Me, Ph, p-MeC6H4) (2) (obtained from (CO)3CpMCH2CCR (1) and Co2(CO)8) to give (CO)3
Cp(CO)2 (3) was further investigated by a crossover experiment. Thus, reaction of an equimolar mixture of 2b (M = W, Cp = η5-C5H5, R = Ph) and 2e (M = W, Cp = η5-C5H4Me; R = p-MeC6H4) with CF3COOH affords only 3b (same M, Cp, and R as 2b) and 3e (same M, Cp, and R as 2e) to show an intramolecular nature of this transformation. Reaction of (CO)3CpWCH2CCPh (1b) with Co4(CO)12 was also examined and found to yield 2b exclusively. Treatment of 1 with Cp2Mo2(CO)4 at 0–5°C provides thermally sensitive compounds, possibly (CO)2Cp
oCp(CO)2 (5), which decompose at room temperature to give Cp2Mo2(CO)6 as the only isolated product. 相似文献
Full-size image (1K)
Full-size image (1K)
17.
Nb4W13O47, a member of the solid solution series Nb8−nW9+nO47 (0?n?5), crystallizes in a threefold superstructure of the tetragonal tungsten bronze structure. While the oxidation of this reduced phase at TOX=1200 °C leads to a separation into the thermodynamically stable phases, lower oxidation temperatures result in products that comprise new structural elements and ordering variants. The characterization of the oxidation products obtained at TOX=1000 °C was performed by scanning transmission electron microscopy applying a high-angle annular dark field detector. At the selected imaging conditions (Z contrast), not only the metal positions are revealed by this technique but valuable additional information about the elemental distribution can be obtained simultaneously. 相似文献
18.
D. P. Domonov S. I. Pechenyuk N. L. Mikhailova A. T. Belyaevskii 《Russian Journal of Inorganic Chemistry》2007,52(7):1027-1032
The thermolysis of the complexes [Co(NH3)6]2C2O4[Cu(C2O4)2]2 (I) and [Co(NH3)6]Cl[Cu(C7H4O3)2] (II) in air and hydrogen at 200, 350, and 500°C and the composition and properties of the thermolysis products are considered.
The oxidative thermolysis of the complexes yields mixtures of cobalt and copper oxides, including mixed ones. The reductive
thermolysis of the complexes yields a Co + Cu bimetallic powder in the case of compound I and a Co + Cu + C powder in the
case of compound II. The thermal behavior of the complexes is governed by the nature of the ligand coordinated to the copper
atom. The observed data are explicable in terms of the properties of this ligand. The chemistry of the oxidative and reductive
thermolysis is discussed.
Original Russian Text ? D.P. Domonov, S.I. Pechenyuk, N.L. Mikhailova, A.T. Belyaevskii, 2007, published in Zhurnal Neorganicheskoi
Khimii, 2007, Vol. 52, No. 7, pp. 1104–1110. 相似文献
19.
The crystal structure of Na7Mg4.5(P2O7)4 has been solved by direct methods from the three-dimensional X-ray data. The space group is . The crystal structure consists of Mg2+, Na+, and P2O4?7 ions. One magnesium atom at symmetry center (0,0,0) and two sodium atoms at ±(?0.0421, ?0.0596, 0.2230) display occupation factors 0.5 each. A short interatomic distance between these Na+ and Mg2+ ions (1.80 ± 0.01 Å) excludes the occupation of both sites in the same unit cell. The crystal structure of Na7Mg4.5(P2O7)4 consists of unit cells containing Na8Mg4(P2O7)4 or Na6Mg5(P2O7)4 with a statistical occurrence 1:1.Each Mg2+ ion is octahedrally coordinated by six O2? ions at distances 1.979 – 2.270 Å. The coordination polyhedra around the Na+ ions are ill-defined. The bond angles POP in the P2O4?7 groups are 126.6 and 133.6° (±0.3°). The final reliability factor R is 7.1%. 相似文献
20.
It is argued that the mixed-valence interpretation of the X-ray photoelectron spectrum of the 4f levels of tungsten in Nax WO3 is more plausible than those based on final-state effects. 相似文献