A spectroscopic and computational investigation of the vanadomolybdate local structure in the lyonsite phase Mg(2.5)VMoO(8)

The vibrational spectrum of Mg2.5VMoO8 obtained by quantum mechanical simulation is compared with the experimentally observed Raman spectrum. This simulation suggests that the observed band at 1016 cm(-1) is attributed to the Mo=O-Mg stretching from two-coordinate oxygen atoms that are adjacent to Mg2+ cation vacancies. Extended X-ray absorption fine structure spectroscopy supports the structural model used to simulate the vibrational modes in Mg2.5VMoO8 that match the observed Raman data.     

Probing the vanadyl and molybdenyl bonds in complex vanadomolybdate structures

A solid solution was found to exist in the quaternary Li(2)O-MgO-V(2)O(5)-MoO(3) system between the two phases Mg(2.5)VMoO(8) and Li(2)Mg(2)(MoO(4))(3). Both Mg(2.5)VMoO(8) and Li(2)Mg(2)(MoO(4))(3) are isostructural with the mineral lyonsite, and substitution according to the formula square(1/4-x/6)Li(4x/3)Mg(15/4-7x/6)V(3/2-x)Mo(3/2+x)O(12) (0 < or = x < or = 1.5, where square denotes a cation vacancy) demonstrates that a complete solid solution exits coupling the addition of molybdenum and lithium with the subtraction of cation vacancies, magnesium, and vanadium and vice versa. Vibrational Raman spectroscopy indicates that molybdenum-oxo double bonds preferentially associate with the cation vacancies.     

Site-specific vanadates Co4Fe3.33(VO4)6 and Mn3Fe4(VO4)6

Single crystals of Co4Fe3.33(VO4)6 and Mn3Fe4(VO4)6 were grown from equivalent CoO/Fe2O3/V2O5 and MnO/Fe2O3/V2O5 melts, respectively. The former crystallizes in the orthorhombic space group Pnma with parameters a = 4.965(1) A, b = 10.211(1) A, c = 17.188(3) A, and Z = 2 and is a homeotype of such catalysts as Mg2.5VMoO8. The latter crystallizes in the triclinic space group P1 with parameters a = 6.703(2) A, b = 8.137(1) A, c = 9.801(2) A, alpha = 105.56(1) degrees, beta = 105.58(2) degrees, gamma = 102.35(1) degrees, and Z = 1 and is a homeotype of beta-Cu3Fe4(VO4)6, the low-pressure form of alpha-Cu3Fe4(VO4)6. The cobalt analogue deviates in stoichiometry from the reactant melt to form the more dense alpha-Cu3Fe4(VO4)6 structure type comprised of partially occupied face-sharing octahedral and trigonal prismatic coordination sites.     

Synthesis, structure, and characterization of novel two- and three-dimensional vanadates: Ba2.5(VO2)3(SeO3)4.H2O and La(VO2)3(TeO6).3H2O

Two new vanadates, Ba(2.5)(VO2)3(SeO3)4.H2O and La(VO2)3(TeO6).3H2O, have been synthesized by hydrothermal methods using BaCO3, Ba(OH)2.H2O, La(NO3)3.6H2O, V2O5, TeO2, and H2SeO3 as reagents. The structures were determined by single-crystal X-ray diffraction. Ba(2.5)(VO2)3(SeO3)4.H2O exhibits a two-dimensional layered structure consisting of VO(5) square pyramids and SeO3 polyhedra, whereas La(VO2)3(TeO6).3H2O has a three-dimensional framework structure composed of VO(4) tetrahedra and TeO6 octahedra. Infrared and Raman spectroscopy, UV-vis diffuse reflectance spectroscopy, and thermogravimetric analysis are also presented. Crystal data: Ba(2.5)(VO2)3(SeO3)4.H2O, trigonal, space group P (No. 147) with a = b = 12.8279(15) A, c = 7.2631(9) A, V = 1035.1(2) A(3), and Z = 2; La(VO2)3(TeO6).3H2O, trigonal, space group R3c (No. 161) with a = b = 9.4577(16) A, c = 23.455(7) A, V = 1816.9(7) A3, and Z = 6.     

Synthesis and structural investigation of a unique columnar phase in the Bi2O3–TeO2–V2O5 System

A new columnar phase Bi(11.65)Te(1.35)V(5)O(34-δ) (δ ～ 1.3) containing VO(4) tetrahedra has been identified for the first time in the Bi(2)O(3)-TeO(2)-V(2)O(5) system. The phase formation and the extent of substitution of Te(4+) for Bi(3+) ions in order to stabilize V(5+) in this composition have been confirmed by the single crystal analysis, combined with the powder X-ray diffraction of the solid state synthesized bulk crystalline samples. The oxide crystallizes in a monoclinic crystal system, space group P2/c, with unit cell parameters a = 11.4616(7) ?, b = 5.7131(3) ?, c = 23.5090(18) ?, β = 101.071° (6) (Z = 2). The structure retains the basic features of the columnar oxides with the presence of [Bi(10.65)Te(1.35)O(14)](n)(9.35n+) columns along the (010) direction, surrounded by (VO(4)) tetrahedra placed in the planes parallel to (100) and (001), with an isolated bismuth atom in between the columns. The composition with a limited Te(4+) substitution, Bi(11.65)Te(1.35)V(5)O(34-δ) (δ ～ 1.3), exists with a surprisingly high oxygen deficiency as compared to the stoichiometrically known columnar oxides such as Bi(13)Mo(4)VO(34), Bi(12)Te(1)Mo(3)V(2)O(34), and Bi(11)Te(2)Mo(2)V(3)O(34). The structure of this interesting member of the columnar family of oxides based on the single crystal X-ray diffraction and the Raman spectroscopic studies indicates the possibility of the distribution of the oxygen vacancies among the VO(4) tetrahedral units. Further confirmation for the formation of vanadium stabilized columnar structures has been provided by the successful preparation of Bi(11.65)Te(1.35)V(4)CrO(34-δ) (δ ～ 0.83) and Bi(11.65)Te(1.35)V(4)WO(34-δ) (δ ～ 0.83) phases. Preliminary investigation of the photocatalytic efficiencies of the oxides Bi(11.65)Te(1.35)V(5)O(34-δ), Bi(11.65)Te(1.35)V(4)CrO(34-δ), and Bi(11.65)Te(1.35)V(4)WO(34-δ) revealed moderate photocatalytic activities for the decomposition of the dyes such as Rhodamine B under UV-vis light irradiation.     

Real-Space Distribution of Local WO(4) Ordering in Negative Thermal Expansive ZrW(2)O(8)

Solids usually expand when they are heated. This is quite common behavior of solids; however, there are some exceptions. Zirconium tungstate (ZrW(2)O(8)) is a prototype material among them, because it has the highest degree of negative thermal expansion (NTE) over broad temperature range. Intensive investigation of NTE mechanisms has suggested the importance of metal-oxygen polyhedra. However, most of the studies have been done with volume-averaged techniques, and microscopic information has been lacking. Here, our electron microscopy observations have unraveled the real-space distribution of local WO(4) tetrahedra ordering for the first time. We have found that (i) the WO(4) ordering is partly inverted; (ii) WO(4) is disordered on the nanoscale; and (iii) doping with scandium enhances the WO(4) disordering. These findings led to construction of a microstructure model for ZrW(2)O(8), providing a new structural perspective for better understanding of local structure and its role in phase transitions.     

A small cavity with reactive internal shell atoms spanned by four {As(W/V)9}-type building blocks allows host-guest chemistry under confined conditions

The reaction of [H2As(III)W18O60]7- with VO2+ and SO4(2-) ions in aqueous solution leads to a V(IV)/V(V) mixed-valence cluster anion containing the {As4M40O140}-type cryptand which has a high formation tendency. An important result is that it exhibits a new type of reactive internal cavity shell. The correspondingly obtained compound Na(NH4)20[{(V(IV)O(H2O))(V(IV)O)2(SO4)2}{(As(III)W9O33)2(As(III)W7.5V(V)1.5O31)2(WO2)4}] x 40 H2O (1), which can also be synthesized from a precursor with the preorganized cryptand, was characterized by elemental and thermogravimetric analyses (determination of crystal water content), redox titrations (determination of the number of V(IV) centers), electronic absorption as well as vibrational spectra, single-crystal X-ray structure analysis (including bond valence sum calculations), and magnetic susceptibility measurements. The relatively small central cavity--formed by the linking of four {AsM9}-type lacunary units (M = W/V) by four WO6 octahedra--allows positioning of a variety of cationic as well as anionic "guests" under confined conditions according to a new approach: replacement of some of the W by V atoms leads to high reactivity of the internal cavity shell as a result of relatively weak VO bonds compared to the WO bonds. This allows an interesting "encapsulation chemistry" with new options. In the present case the cavity contains besides an arrangement of three V(IV) centers, two sulfate groups that replace O atoms of the {AsM9} units as well as an interesting hydrogen bond situation.     

New quaternary tellurite and selenite: synthesis, structure, and characterization of centrosymmetric InVTe2O8 and noncentrosymmetric InVSe2O8

Two new quaternary mixed metal oxide materials--InVTe(2)O(8) and InVSe(2)O(8)--have been synthesized, as crystals and pure bulk powders by standard solid-state reactions using In(2)O(3), V(2)O(5), and TeO(2) (or SeO(2)) as reagents. The crystal structures of the reported materials were determined using single-crystal X-ray diffraction. InVTe(2)O(8) crystallizes in the monoclinic centrosymmetric space group P2(1)/n (No. 14), with unit-cell parameters of a = 7.8967(16) ?, b = 5.1388(10) ?, c = 16.711(3) ?, β = 94.22(3)°, and Z = 4, and InVSe(2)O(8) crystallizes in the noncentrosymmetric space group Pm (No. 6) with unit-cell parameters of a = 4.6348(9) ?, b = 6.9111(14) ?, c = 10.507(2) ?, β = 97.77(3)°, and Z = 2. While the centrosymmetric InVTe(2)O(8) shows a two-dimensional (2D) layered structure composed of InO(6) octahedra, VO(4) tetrahedra, and TeO(4) polyhedra, the noncentrosymmetric InVSe(2)O(8) exhibits a three-dimensional (3D) framework structure with distorted InO(6) octahedra, VO(5) square pyramids, and SeO(3) polyhedra. Powder second-harmonic generation (SHG) measurements on InVSe(2)O(8), using 1064-nm radiation, indicate that the material has a SHG efficiency ~30 times that of α-SiO(2). Additional SHG measurements reveal that the material is not phase-matchable (Type 1). Infrared, ultraviolet-visible light (UV-vis) diffuse reflectance, and thermogravimetric analyses for the two compounds are also presented, as are dipole moment calculations.     

Hydrothermal synthesis and comparative coordination chemistry of new rare-earth V4+ compounds

Several new hydrated rare earth vanadates and rare earth oxy-vanadates have been synthesized using hydrothermal techniques and characterized using single crystal and powder X-ray diffraction and infrared and UV-vis absorption spectroscopies. The hydrated rare earth vanadates adopt the space group P2(1)/m with general formula A(3)VO(5)(OH)(3) (A = Y (1), Dy (2), or La (3)) and contain anionic distorted square pyramidal [VO(5)](-6) units and AO(7) and AO(8) polyhedra. The oxy-vanadates with the general formula A(2)O(VO(4)) (A = Y (4), Dy (5; 6), or Yb (7)) form two polymorphs in either P2(1)/c or C2/c space groups and contain anionic tetrahedral [VO(4)](-4) units and nonvanadium bonded O(2-) anions in distorted [OA(4)] tetrahedra. In all cases, the vanadium ion is in the tetravalent oxidation state, and its original source was the trace V(4+) impurities in YVO(4). The observed vanadyl and equatorial vanadium-oxygen bond lengths about the square pyramid in compounds 1-3 and the tetrahedral vanadium coordination found in compounds 4-7 are unusual for V(4+). The electronic and vibrational spectra are also reported and correlated with the appropriate coordination environment.     

Comprehensive interpretation of a substitution effect on an order-disorder phase transition in A(1-x)MxW2O(8-y) (A = Zr, Hf; M = trivalent cations) and other ZrW2O8-based solid solutions

Hf(1-x)Lu(x)W(2)O(8-y) solid solutions up to x = 0.04, based on a negative thermal expansion material HfW(2)O(8), were synthesized by a solid state reaction method. X-ray diffraction experiments of these solid solutions from 90 to 560 K indicated thermal contraction with increasing temperature. Temperatures of order-disorder phase transition (T(trs)) associated with the orientation of WO(4) tetrahedra were determined from disappearance of a characteristic diffraction peak (310). The T(trs) of the solid solutions drastically decreased with increasing Lu content. Saturated order parameters (eta(s)) associated with the orientational order of the WO(4) pairs were estimated from the characteristic diffraction peak at sufficient low temperature. These behaviors of Hf(1-x)Lu(x)W(2)O(8-y) are consistent with those of Zr(1-x)M(x)W(2)O(8-y) (M = Sc, Y, In, Lu). The drastic suppression of T(trs) in Hf(1-x)Lu(x)W(2)O(8-y) can be interpreted in the framework of a model proposed for Zr(1-x)M(x)W(2)O(8-y), which states the existence of a local nanoregion including the WO(4) pairs having the frozen-in orientational disorder. To understand the substitution effect on the order-disorder phase transition comprehensively, classification based on the saturated order parameter eta(s) of the phase transition of AW(2)O(8) (A = Hf, Zr)-based solid solutions was carried out and discussed.     

Structure and properties of the thorium vanadyl tellurate, Th(VO2)2(TeO6)(H2O)2

The hydrothermal reaction of Th(NO3)4.xH2O with V2O5 and H6TeO6 at 200 degrees C under autogenously generated pressure results in the formation of Th(VO2)2(TeO6)(H2O)2 as a pure phase. The single-crystal X-ray data indicate that Th(VO2)2(TeO6)(H2O)2 possesses a three-dimensional structure constructed from ThO9 tricapped trigonal prisms, VO5 distorted square pyramids, VO4 distorted tetrahedra, and TeO6 distorted octahedra. Both of the vanadium polyhedra contain VO2+ vanadyl units with two short V=O bond distances. The tellurate octahedron is tetragonally distorted and utilizes all of its oxygen atoms to bond to adjacent metal centers, sharing edges with ThO9 and VO5 units, and corners with two ThO9, one VO5, and two VO4 polyhedra. Crystallographic data: Th(VO2)2(TeO6)(H2O)2, orthorhombic, space group Pbca, a = 12.6921(7), b = 11.5593(7), c = 13.0950(8) A, Z = 8 (T = 193 K). The UV-vis diffuse reflectance spectrum of Th(VO2)2(TeO6)(H2O)2 shows vanadyl-based charge-transfer absorption features. Th(VO2)2(TeO6)(H2O)2 decomposes primarily to Th(VO3)4 when heated at 600 degrees C in air.     

Probing the effect of local structure on the thermodynamic redox properties of V(+5): a comparison of V2O5 and Mg3(VO4)2

Coulometric titration, an electrochemical method for measuring oxidation isotherms, has been used to characterize the redox properties of V2O5 and Mg3(VO4)2 between 823 and 973 K. V2O5 shows distinct regions in the isotherms corresponding to equilibrium with mixtures of V2O3 and V2O4 and of V2O4 and V2O5. From this data, the enthalpies for oxidation of V2O3 to V2O4 and for V2O4 to V2O5 are shown to be -380 +/- 10 and -285 +/- 20 kJ mol-1 O2, respectively. Oxidation isotherms for Mg3(VO4)2 exhibit a single step between the oxidized sample (all V+5) and a completely reduced sample (all V+3). The enthalpy of oxidation is found to increase with the oxidation state of the sample, from -370 +/- 30 kJ mol-1 O2 at an O:V ratio of 1.5 to -460 +/- 10 kJ mol-1 O2 at an O:V ratio of 2.5.     

Raman spectroscopic study of tungsten(VI) oxosulfato complexes in WO3-K2S2O7-K2SO4 molten mixtures: stoichiometry, vibrational properties, and molecular structure

The dissolution reaction of WO3 in pure molten K2S2O7 and in molten K2S2O7-K2SO4 mixtures is studied under static equilibrium conditions in the XWO3(0) = 0-0.33 mol fraction range at temperatures up to 860 °C. High temperature Raman spectroscopy shows that the dissolution leads to formation of W(VI) oxosulfato complexes, and the spectral features are adequate for inferring the structural and vibrational properties of the complexes formed. The band characteristics observed in the W=O stretching region (band wavenumbers, intensities, and polarization characteristics) are consistent with a dioxo W(=O)2 configuration as a core unit within the oxosulfato complexes formed. A quantitative exploitation of the relative Raman intensities in the binary WO3-K2S2O7 system allows the determination of the stoichiometric coefficient, n, of the complex formation reaction WO3 + nS2O7(2-) --> C(2n-). It is found that n = 1; therefore, the reaction WO3 + S2O7(2-) > WO2(SO4)2(2-) with six-fold W coordination is proposed as fully consistent with the observed Raman features. The effects of the incremental dissolution and presence of K2SO4 in WO3-K2S2O7 melts point to a WO3 · K2S2O7 · K2SO4 stoichiometry and a corresponding complex formation reaction in the ternary molten WO3-K2S2O7-K2SO4 system according to WO3 + S2O7(2-) + SO4(2-) --> WO2(SO4)3(4-). The coordination sphere of W in WO2(SO4)2(2-) (binary system) is completed with two oxide ligands and two chelating sulfate groups. A dimeric [{WO2(SO4)2}2(μ-SO4)2](8-) configuration is proposed for the W oxosulfato complex in the ternary system, generated from inversion symmetry of aWO2(SO4)3(4-) moiety resulting in two bridging sulfates. The most characteristic Raman bands for the W(VI) oxosulfato complexes pertain to W(=O)2 stretching modes (i) at 972 (polarized) and 937 (depolarized) cm(-1) for the ν(s) and ν(as) W(=O)2 modes of WO2(SO4)2(2-), and (ii) at 933 (polarized) and 909 (depolarized) cm(-1) for the respective modes of [{WO2(SO4)2}2(μ-SO4)2](8-).     

Structural influences of organonitrogen ligands on vanadium oxide solids. Hydrothermal syntheses and structures of the terpyridine vanadates [V2O4(terpy)2]3[V10O28], [VO2(terpy)][V4O10], and [V9O22(terpy)3

Hydrothermal reactions of the V2O5/2,2':6':2"-terpyridine/ZnO/H2O system under a variety of conditions yielded the organic-inorganic hybrid materials [V2O4(terpy)2]3[V10O28].2H2O (VOXI-10), [VO2(terpy)][V4O10] (VOXI-11), and [V9O22(terpy)3] (VOXI-12). The structure of VOXI-10 consists of discrete binuclear cations [V2O4(terpy)2]2+ and one-dimensional chains [V10O28]6-, constructed of cyclic [V4O12]4- clusters linked through (VO4) tetrahedra. In contrast, the structure of VOXI-11 exhibits discrete mononuclear cations [VO2(terpy)]1+ and a two-dimensional vanadium oxide network, [V4O10]1-. The structure of the oxide layer is constructed from ribbons of edge-sharing square pyramids; adjacent ribbons are connected through corner-sharing interactions into the two-dimensional architecture. VOXI-12 is also a network structure; however, in this case the terpy ligand is incorporated into the two-dimensional oxide network whose unique structure is constructed from cyclic [V6O18]6- clusters and linear (V3O5(terpy)3) moieties of corner-sharing vanadium octahedra. The rings form chains through corner-sharing linkages; adjacent chains are connected through the trinuclear units. Crystal data: VOXI-10, C90H70N18O42V16, triclinic P1, a = 12.2071(7) A, b = 13.8855(8) A, 16.9832(10) A, alpha = 69.584(1) degrees, beta = 71.204(1) degrees, gamma = 84.640(1) degrees, Z = 1; VOXI-11, C15H11N3O12V5, monoclinic, P2(1)/n, a = 7.7771(1) A, b = 10.3595(2) A, c = 25.715(4) A, beta = 92.286(1) degrees, Z = 4; VOXI-12, C45H33N9O22V9, monoclinic C2/c, a = 23.774(2) A, b = 9.4309(6) A, c = 25.380(2) A, beta = 112.047(1) degrees, Z = 4.     

New luminescent solids in the Ln-W(Mo)-Te-O-(Cl) systems

Solid-state reactions of lanthanide(III) oxide (and/or lanthanide(III) oxychloride), MoO3 (or WO3), and TeO2 at high temperature lead to eight new luminescent compounds with four different types of structures, namely, Ln2(MoO4)(Te4O10) (Ln = Pr, Nd), La2(WO4)(Te3O7)2, Nd2W2Te2O13, and Ln5(MO4)(Te5O13)(TeO3)2Cl3 (Ln = Pr, Nd; M = Mo, W). The structures of Ln2(MoO4)(Te4O10) (Ln = Pr, Nd) feature a 3D network in which the MoO4 tetrahedra serve as bridges between two lanthanide(III) tellurite layers. La2(WO4)(Te3O7)2 features a triple-layer structure built of a [La2WO4]4+ layer sandwiched between two Te3O72- anionic layers. The structure of Nd2W2Te2O13 is a 3D network in which the W2O108- dimers were inserted in the large tunnels of the neodymium(III) tellurites. The structures of Ln5(MO4)(Te5O13)(TeO3)2Cl3 (Ln = Pr, Nd; M = Mo, W) feature a 3D network structure built of lanthanide(III) ions interconnected by bridging TeO32-, Te5O136-, and Cl- anions with the MO4 (M = Mo, W) tetrahedra capping on both sides of the Ln4 (Ln = Pr, Nd) clusters and the isolated Cl- anions occupying the large apertures of the structure. Luminescent studies indicate that Pr2(MoO4)(Te4O10) and Pr5(MO4)(Te5O13)(TeO3)2Cl3 (M = Mo, W) are able to emit blue, green, and red light, whereas Nd2(MoO4)(Te4O10), Nd2W2Te2O13, and Nd5(MO4)(Te5O13)(TeO3)2Cl3 (M = Mo, W) exhibit strong emission bands in the near-IR region.     

Hydrothermal Synthesis, Structural Characterization and Properties of Mixed Valent Decavanadium Oxide [Co_2Cl_8V_(10) O_(18)(H_2O)]Cl_2·6H_2O with Novel Three-dimensional Framework

IntroductionPolyoxometalates constitute an enormous classof compounds whose unusual versatility and reac-tivity afford practical applications to many fields,such as catalysis,biology,medicine,and materialsciences[1— 4] .In recent years,hydrothermal tech-nique has become a vital tool in self- assemblychemistry.This technique,in combination with or-ganic templates,has been demonstrated to be wellsuited for the synthesis and the crystal growth ofpolyoxometalates with novel structures[5— 9] .Amo…     

Solid state coordination chemistry of the copper(ii)-terpyridine/oxovanadium organophosphonate system: hydrothermal syntheses, structural characterization and magnetic properties

The hydrothermal reactions of CuSO4.5H2O, Na3VO4, 2,2':6':2'-terpyridine (terpy), and the appropriate organophosphonate ligand yield a series of materials of the Cu(ii)-terpy/oxovanadium organophosphonate family. The complexes exhibit distinct structures spanning one-, two- and three-dimensions and exhibiting diverse oxovanadium building blocks. Thus, [{Cu(terpy)}(V2O4)(O3PPh)(HO3PPh)2] (1) is one-dimensional and constructed from binuclear units of corner-sharing V(v) square pyramids. While [{Cu(terpy)}VO(O3PCH2PO3)] (2), [{Cu(terpy)}2(V4O10)(O3PCH2CH2PO3)] (3), and [{Cu(terpy)}(V2O4){O3P(CH2)3PO3}].2.5H(2)O (4.2.5H2O) are similarly one-dimensional, the V/O structural components consist of isolated V(iv) square pyramids, tetranuclear V(v) units of three tetrahedra and one square pyramid in a corner-sharing arrangement, and isolated V(v) tetrahedra and square pyramids, respectively. The second propylenediphosphonate derivative, [{Cu(terpy)}(V2O4){O3P(CH2)3PO3}] (5) is three-dimensional and exhibits isolated V(v) tetrahedra as the vanadate component. The two-dimensional structure of [{Cu(terpy)(H2O)}(V3O6){O3P(CH2)4PO3}] (6) is mixed valence with isolated V(iv) square pyramids and binuclear units of corner-sharing V(v) tetrahedra providing the V/O substructures.     

新型环形聚阴离子[{WO(H_2O)}_3(AsW_8O31)_3]~21-的结构及表征

在pH=3.0的水溶液中，Na_2WO_4·2H_2O与NaAsO_2·6H_2O和NH_4Cl反应，得 到了新的杂多钨酸盐(MH_4)_19Na_2[{WO(H_2O)}_3(AsW_8O31)_3]·45H_2O单晶， 用X射线单晶衍射法及元素分析确定了其结构，晶体属单斜晶系，空间群C2/c，晶 胞参数为：a=3.1165(11)nm, b=1.7388(7)nm, c=2.2789(9)nm, β=97.342(6)°, V=12.248(8)nm~3, Z=4, R_1=0.0571,wR_2=0.0741[I＞2σ(I)]. 环型聚阴离子 [{WO(H_2O)}_3(AsW_8O31)_3]~21-是由三个{WO(H_2O)}桥连三个新发现的 {AsW_8O31}单元构成的，环聚离子[{WO(H_2O)}_3(AsW_8O31)_3]~21-具有近似D_ (3h)对称性。对该化合物还进行了~183W NMR, IR和TG表征。     

Oxygen Abstraction Reactions of N-Substituted Hydroxamic Acids with Molybdenum(V) and Vanadium(III) and -(IV) Compounds

A wide range of N-substituted mono- and dihydroxamic acids undergo oxygen abstraction on reaction with V(III), V(IV), and Mo(V) compounds to form hydroxamates of V(V) and Mo(VI) respectively together with the corresponding amides and diamides. The molybdenyl and vanadyl hydroxamates form metal-oxygen clusters under FABMS conditions. The X-ray crystal structures of [MoO(2){CH(3)(CH(2))(n)()C(O)N(C(6)H(5))O}(2) (1 and 2) (n = 4, 5) show monomeric structures with structural trans effects and consequent weakening of the Mo-O(ligand) bonds which may account for the tendency to form clusters in FABMS. In constrast, the electrospray MS of the vanadyl dihydroxamates, VO(OH)[PhN(O)C(O)(CH(2))(n)()C(O)N(O)Ph] (n = 3, 5) and VO(OH)[p-CH(3)C(6)H(4)N(O)C(O) (CH(2))(n)()C(O)N(O)C(6)H(4)-CH(3)) (n = 2, 4) show the presence of dimers in solution.     

Syntheses and crystal structures of a series of alkaline earth vanadium selenites and tellurites

Six new novel alkaline-earth metal vanadium(V) or vanadium(IV) selenites and tellurites, namely, Sr(2)(VO)(3)(SeO(3))(5), Sr(V(2)O(5))(TeO(3)), Sr(2)(V(2)O(5))(2)(TeO(3))(2)(H(2)O), Ba(3)(VO(2))(2)(SeO(3))(4), Ba(2)(VO(3))Te(4)O(9)(OH), and Ba(2)V(2)O(5)(Te(2)O(6)), have been prepared and structurally characterized by single crystal X-ray diffraction analyses. These compounds exhibit six different anionic structures ranging from zero-dimensional (0D) cluster to three-dimensional (3D) network. Sr(2)(VO)(3)(SeO(3))(5) features a 3D anionic framework composed of VO(6) octahedra that are bridged by SeO(3) polyhedra. The oxidation state of the vanadium cation is +4 because of the partial reduction of V(2)O(5) by SeO(2) at high temperature. Ba(3)(VO(2))(2)(SeO(3))(4) features a 0D [(VO(2))(SeO(3))(2)](3-) anion. Sr(V(2)O(5))(TeO(3)) displays a unique 1D vanadium(V) tellurite chain composed of V(2)O(8) and V(2)O(7) units connected by tellurite groups, forming 4- and 10-MRs, whereas Sr(2)(V(2)O(5))(2)(TeO(3))(2)(H(2)O) exhibits a 2D layer consisting of [V(4)O(14)] tetramers interconnected by bridging TeO(3)(2-) anions with the Sr(2+) and water molecules located at the interlayer space. Ba(2)(VO(3))Te(4)O(9)(OH) exhibits a one-dimensional (1D) vanadium tellurite chain composed of a novel 1D [Te(4)O(9)(OH)](3-) chain further decorated by VO(4) tetrahedra. Ba(2)V(2)O(5)(Te(2)O(6)) also features a 1D vanadium(V) tellurites chain in which neighboring VO(4) tetrahedra are bridged by [Te(2)O(6)](4-) dimers. The existence of V(4+) ions in Sr(2)(VO)(3)(SeO(3))(5) is also confirmed by magnetic measurements. The results of optical diffuse-reflectance spectrum measurements and electronic structure calculations based on density functional theory (DFT) methods indicate that all six compounds are wide-band gap semiconductors.