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1.
This paper reports a comparative study of the non-isothermal decompositions of the heteropolyacids HPM and HPVM, with structures
consisting of Keggin units (KUs). Non-isothermal analysis at low heating rates demonstrated the existence of 4 crystal hydrate
species, depending on the temperature. The stability domains of the anhydrous forms of HPM and HPVM were found to be 150–380°C,
respectively. Processing of the TG curves obtained at different heating rates by the Ozawa method revealed that the decomposition
of anhydrous HPM takes place according to a unitary mechanism, whilst for anhydrous HPVM two mechanisms are observed. Thus,
the first part of the constitution water is lost simultaneously with the departure of vanadium from the KU as VO2+, while the second part is lost at higher temperatures as in the case HPM.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
It has been established by XRD, DTA and TG methods that phases of solid solution type of MoO3 in SbVO5 are formed in the system V2O5-MoO3-a-Sb2O4. The Mo6+ ions are incorporated into the crystal lattice of SbVO5 instead of both Sb5+ and V5+, while the charge compensation occurs by a formation of cation defects (□) at Sb5+ and V5+. The phases Sb1-6x
□
xV1-6x
□
xMo10xO5 are stable in the solid-state up to 690±10°C and the limit of solubility of MoO3 in SbVO5 does not exceed 20.00 mol%.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
《Journal of Coordination Chemistry》2012,65(23):3754-3762
Two new organic–inorganic hybrid cobalt-molybdovanadates [Co(phen)3]H2[H2V2Mo6O26] · 7H2O (1) and [Co(2,2′-bipy)3][Na(H2O)7][VMo12O40] (2) have been hydrothermally synthesized and structurally characterized by elemental analyses, IR, UV, XPS spectroscopy, thermogravimetric (TG) analyses, and X-ray single crystal diffraction. The molecular structure of 1 consists of a [V2Mo6(OH)2O24]4? polyoxoanion, a [Co(phen)3]2+, two H+ and seven lattice water molecules. The structure of [V2Mo6(OH)2O24]4? consists of six MoO6 octahedra and two VO4 tetrahedra; six MoO6 octahedra are linked by edge-sharing oxygens forming a {Mo6} ring, and two VO4 tetrahedra cap opposite sides of the {Mo6} ring. The molecular structural unit of 2 is constructed from a typical Keggin-type [VMo12O40]3? polyoxoanion and a [Co(2,2′-bipy)3]2+ cation and a Na+ countercation; Co2+ is coordinated by six nitrogens from three 2,2′-bipyridines forming a distorted octahedron. 相似文献
4.
Evgeny V. Nazarchuk Oleg I. Siidra Dr. Sergey V. Krivovichev Thomas Malcherek Wulf Depmeier 《无机化学与普通化学杂志》2009,635(8):1231-1235
Two new mixed alkaline uranyl molybdates CsNa3[(UO2)4O4Mo2O8] ( 1 ) and Cs2Na8[(UO2)8O8(Mo5O20)] ( 2 ) have been obtained by high‐temperature solid state reactions. Their crystal structures have been solved by direct methods: Compound 1 : triclinic, P , a = 6.46(1), b = 6.90(1), c = 11.381(2) Å, α = 84.3(1), β = 91.91(1), γ = 80.23(1)°, V = 488.6(2) Å3, R1 = 0.06 for 2865 unique reflections with |Fo| ≥ 4σF; Compound 2 : orthorhombic, Ibam, a = 6.8460(2), b = 23.3855(7), c = 12.3373(3) Å, V = 1975.2(1) Å3, R1 = 0.049 for 2120 unique reflections with |Fo| ≥ 4σF. The structure of 1 contains complex sheets of UrO5 pentagonal bipyramids and molybdenum polyhedra. The sheets have [(UO2)2O2(MoO5)] composition. Natrium and cesium atoms are located in the interlayer space. Cesium atoms are situated between the molybdenum clusters, whereas natrium atoms are segregated between the uranyl complexes. The large Cs+ ions are localized between the Mo2O9 groups and force the molybdenum polyhedra to rotate relative to the [(UO2)2O2(MoO5)] sheets. Such rotation is impossible for U6+ polyhedra due to their rigid edge‐sharing complexes. The distance between the U6+ polyhedra vertices of neighboring layers is 3.8 Å, that allows the Na+ ion to be positioned between the uranyl groups. The crystal structure of 2 is based upon a framework consisting of [(UO2)2O2(MoO5)] sheets parallel to (010). The sheets are linked into a 3‐D framework by sharing vertices with the Mo(2)O4 tetrahedra, located between the sheets. Each MoO4 tetrahedron shares two of its corners with two MoO6 octahedra in the sheet above, and the other two with MoO6 octahedra of the sheet below. Thus four MoO6 octahedra and one MoO4 tetrahedron form chains of composition Mo5O18. The resulting framework has a system of channels occupied by the Cs+ and Na+ ions. 相似文献
5.
The dissociation state of the solutes M2MoO4, M2Mo3O10, M2Mo4O13, M2Mo5O16 (MRb or Cs), Na2CrO4·MoO3, K2CrO4·2 MoO3, Cr2Mo3O12 and V2MoO8 was studied cryoscopically in molten K2 Cr2O7 and KNO3 solvents. The freezing point depression, ΔT, of the solvents was obtained by measuring the cooling curves of the binary salt mixtures over unlimited range of solute concentration. The number of foreign ions obtained ν, showed that the solutes were either simply dissociated in the melt into the probable stable species (MoO4)2?, (Mo3O10)2?, (Mo4O13)2? and (Mo5O16)2? or, in some cases after reactions and rearrangements, into (CrMo2O10)2? heteropolyions. The solute V2MoO8, on the other hand, was found to dissolve without any apparent dissociation. An agreement between the experimental and calculated values of activity, a, based on the Temkin and Random Mixing models and that of Van't Hoff's equation support the proposed simple dissocia- tion scheme for K2Cr2O7Cs2MoO4 system. 相似文献
6.
Thermal studies on various oxalato complexes have been of immense interest as they yield finely divided, highly reactive oxides which are usually obtained at a much lower temperature than that required in the conventional method of preparation, i.e., heating a mixture of two or more constituents [1]. A survey of the literature reveals that the compounds having the general formula A2[Mo2O5(C2O4)2(H2O)2], where A = K+, NH+4[2] and A = Cs+ [3], have been prepared and their thermal decomposition is studied, but no such information is available regarding the preparation and characterisation of Na2[Mo2O5(C2O4)2(H2O)2] (SMO), which forms the subject of study of this paper. Sodium dimolybdate (Na2Mo2O7), the decomposition product of SMO, is obtained at 280°C, a temperature much lower than that required in the conventional method of preparation of heating a mixture of Na2MoO4 and MoO3 [4]. 相似文献
7.
The V4+ content in V2O5 doped with MoO3 is measured by a spectroscopic method. The influence of the oxygen pressure is also considered. Up to roughly 3.5 at.-% Mo/(Mo+V) the V4+ fraction is equal to the Mo6+ fraction for samples sintered in air. Increase of PO2 gives a decrease in the measured values of the V4+ fraction for the 5, 10 and 33 at.-% Mo-doped samples. 相似文献
8.
Investigation on the Ternary System V/Mo/O During chemical transport reactions mixtures of pseudo-binary line of intersection V2O5/MoO3 are separated into two phases, the V2O5-(α) phase, which MoO3-content depends on the oxygen partial pressure during the deposition and the MoO3 phase which contains no more than 1% (n/n) V2O5. Ternary compounds do not exist on the pseudo-binary line. V9Mo6O40 is formed by the reaction of V2O5 and MoO3 (3:2) under exclusion of oxygen. The compound may be chemically transported under the own oxygen coexistence pressure. It was shown by total pressure measurements of V2O5/MoO3 starting mixtures that the insertion of MoO3 in the α-phase and the formation of the V9Mo6O40 phase respectively is connected with elimination of oxygen and the reduction of VV to VIV in equivalence of the quantity of incorporated MoO3. 相似文献
9.
Lee Martin Anthony Christian Hiroki Akutsu 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(6):m157-m159
The title compound, Cs3[Cr(C2O4)3]·2H2O, has been synthesized for the first time and the spatial arrangement of the cations and anions is compared with those of the other members of the alkali metal series. The structure is built up of alternating layers of either the d or l enantiomers of [Cr(oxalate)3]3−. Of note is that the distribution of the [Cr(oxalate)3]3− enantiomers in the Li+, K+ and Rb+ tris(oxalato)chromates differs from those of the Na+ and Cs+ tris(oxalato)chromates, and also differs within the corresponding BEDT‐TTF [bis(ethylenedithio)tetrathiafulvalene] conducting salts. The use of tris(oxalato)chromate anions in the crystal engineering of BEDT‐TTF salts is discussed, wherein the salts can be paramagnetic superconductors, semiconductors or metallic proton conductors, depending on whether the counter‐cation is NH4+, H3O+, Li+, Na+, K+, Rb+ or Cs+. These materials can also be superconducting or semiconducting, depending on the spatial distribution of the d and l enantiomers of [Cr(oxalate)3]3−. 相似文献
10.
About a New Copper Molybdate: Cu4Mo5O17 Single crystals of Cu4Mo5O17 were prepared by solid state reaction of Cu2O and MoO3 in the absence of oxygen. Single crystal X-ray investigations lead to triclinic symmetry (space group P1, a = 6.782, b = 9.573, c = 10.948 Å; α = 107.03, β = 88.40, γ = 111.02°, Z = 2). Cu4Mo5O17 shows crystal chemical differences in respect to the CuII-oxomolybdates. The differences concern the coordination of Mo6+. Cu+ formes not a linear O? Cu? O group but is surrounded by oxygen tetrahedrally and octahedrally. The crystal structure is described and discussed. 相似文献
11.
Ting-Yan Lan Jian-Xin Chen Xiu-Qing Lü Yuan-Biao Huang Zhong-Shui Li Chun-Xia Wei Zhi-Chun Zhang 《Structural chemistry》2006,17(1):35-41
Two Keggin-type phosphododecamolybdate compounds [Cd(2,2′-bpy)3]2[PMoVMoVI
11O40] (1) and [H3PMo12O40]·3(4,4′-bpy)·4H2O (2) (bpy=bipyridine) were prepared by the hydrothermal method for the first time and characterized by elemental analyses, X-ray
single-crystal diffraction, ESR spectra, and IR spectra, showing that compound 1 consists of a mixed valence Keggin polyanion [PMoVMoVI
11O40]4− and two isolated coordinated cations [Cd(2,2′-bpy)3]2+, while compound 2 is an intermolecular compound based on organic substrate 4,4′-bpy and heteropoly acid unit H3PMo12O40. Furthermore, both the compounds show strong photoluminescence properties in the solid state at room temperature. The catalytic
activities of the two compounds were also determined by the oxidation of benzaldehyde to benzoic acid using H2O2 as oxidant in a liquid–solid triphase system. 相似文献
12.
The results concerning the synthesis, structure and thermal properties of V2O5-MoO3-Ag2O samples in the molybdenum rich region of ternary system are presented in the form of quasi-binary systems: β-AgVO3-β-Ag2MoO4, AgVMoO6-MoO3, AgVMoO6-Ag2Mo4O13, AgVMoO6-Ag2Mo2O7, AgVMoO6-β-Ag2MoO4 and also of the system in which at V2O5/MoO3 molar ratio 3:7 the content of Ag2O was variable. The ternary phase AgVMoO6 was not described earlier in the literature. 相似文献
13.
I. V. Mironov 《Russian Chemical Bulletin》1998,47(10):1864-1867
The influence of the ion background (NaClO4, LiClO4, and HClO4) on the kinetics of the reaction PtdientH2O2++X−→PtdientX++H2O(X=Cl, Br, I, SCN, and N3) was studied at 25°C by spectrophotometry. Changes in the rate constant with increase in the ionic strength are described
by the Debye-Hückel and Gosh-Bjerrum equations. The reaction PtdienCl++H2O→PtdientH2O2++Cl− was studied by potentiometry and its rate constant was established to depend weakly on variations of the medium.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1918–1921, October, 1998. 相似文献
14.
A Contribution on CuPrMo2O8 and CuTbMo2O8 Single crystals of (I): CuPrMo2O8 and (II): CuTbMo2O8 were prepared by solid state reactions in closed copper tubes. They crystallize with orthorhombic symmetry, space group D-Pbca, (I): a = 10.4114, b = 9.8917, c = 14.8287 Å, (II): a = 10.2243, b = 9.7385, c = 14.6000, Z = 8. Both compounds are isotypic to CuYMo2O8, showing isolated MoO4 tetrahedra, square antiprismatic coordination of Ln3+ and Cu+ besides one edge of an O2? triangle. Calculations of the coulombterm of lattice energy support the oxidation state Cu2+ in combination with mixed valences of Mo6+ and Mo5+ on the molybdenum point positions. 相似文献
15.
Tien The Nguyen Thang Minh Le Duc Duc Truong Rasmus Fehrmann Anders Riisager Isabel Van Driessche 《Research on Chemical Intermediates》2012,38(3-5):829-846
In this work, the possible synergy effects between Bi2O3, MoO3 and V2O5, and between Bi2Mo3O12 and BiVO4, were investigated. The catalytic activity of the ??mechanical mixture?? of these compounds was measured. The mixture containing 36.96?mol% Bi2O3, 39.13?mol% MoO3 and 23.91?mol% V2O5 (21.43?mol% Bi2Mo3O12 and 78.57?mol% BiVO4), corresponding to the compound Bi1?x/3V1?x Mo x O4 with x?=?0.45 (Bi0.85V0.55Mo0.45O4), exhibited the highest activity for the selective oxidation of propylene to acrolein. The mixed sample prepared chemically by a sol?Cgel method possessed higher activity than that of mechanical mixtures. 相似文献
16.
New mixed valent molybdenum monophosphates AMo3P2O14 have been synthesized for A = Ag, Rb, Na, Sr. The single crystal X-ray diffraction study of two of them (A = Ag, Sr) shows that they belong to the layer structure type KMo3P2O14. Their structure consists of [Mo3P2O14]∞ layers involving MoO6 octahedra and MoO5 bipyramids, interleaved with A cations forming bicapped trigonal prisms AO8. Bond valence calculations show a localisation of the MoV and MoVI species according to the formula A1MoVoct1MoVIoct2MoVIbipyP2O14 for A = Ag, Na and SrMoVoct1MoVoct2MoVIbipyP2O14. A comparison between the different MoV? MoVI phosphates is made. 相似文献
17.
Sofiane Bouazza Diala Salloum Régis Gautier Patrick Gougeon Michel Potel Didier Hauchard 《Journal of Cluster Science》2009,20(1):133-143
Owing to the high lability of cations in the three-dimensional framework of K1+x
Mo12S14 (0 ≤ x ≤ 1.6), first-principles calculations and electrochemical methods have been carried out to study the insertion of cations
in the empty channels of this compound. The cavity microelectrode that is a suitable electrode for powder material analysis
has been used in voltammetric experiments. Results obtained for Li+, Na+, Rb+, K+, Cs+ and NH4
+ cations are presented and discussed. 相似文献
18.
Jiqing Xu Renzhang Wang Chunxiao Guo Guoyu Yang Qingxin Zeng Weiming Bu Ling Ye Yuguo Fan Guangdi Yang 《中国科学B辑(英文版)》2001,44(2):137-146
A nickel-1,10-phenanthroline complex supported on an octamolybdate, [(Ni(phen)2
2(ξ-Mo8O26)], has been hydrothermally synthesized with MoO3, H2MoO4, Ni(OAc)2 6H3O and 1,10-phenathroline (1,10-phen) as raw materials. The crystals of the compound belong to monoclinic P21/n space group,a = 1.2952(2),b = 1.6659(10),c = 1.3956(12) nm, β =106.273(8)°,V = 2.8906(5) nm3,Z = 2. 5604 observable reflections (I >2σ(I)) were used for structure resolution and refinements to converge to finalR
1 = 0.0414,wR
2 = 0.0815. The result of structure determination shows that the compound contains octamolybdate possessing a novel structure
type (named as ξ-isomer). The feature of ξ-[Mo8O26]4- is that it is composed of Mo6O6 ring and two MoO6 octahedral located at cap positions on opposite faces. The Mo6O6 ring contains two octahedral and four trigonal-bipyramidal MoVI atoms. Each ξ-[Mo8O26]4- unit is bonded with two [Ni(phen)2]2+ through terminal oxygen atoms of octahedral and neighbouring trigonal-bipyramidal Mo atom in the Mo6O6 ring. IR and UV-Vis spectra of the compound were measured and its electronic structure was studied by EHMO method. 相似文献
19.
The depression of freezing point of molten K2Cr2O7 and KNO3 as solvents was measured after addition of small concentrations of the following compounds: to K2Cr2O7: MoO3, CrO3, (NH4)2CrO4, K2MoO4, Na2MoO4, Li2MoO4, and Na2Mo2O7, respectively; to KNO3: CrO3, (NH4)2Cr2O7 K2Cr2O7, K2CrO4 and MoO3, (NH4)6(Mo7O24) · 4 H2O, K2Mo2O7, K2MoO4, Na2MoO4 and Li2MoO4, respectively. It could be concluded from the measured values of the freezing point depression if a reaction between solvent and solute took place. 相似文献