The electronic structure of FeO 4 2− , RuO4, RuO 4 − , RuO 4 2− and OsO4 by the HFS-DVM method

The electronic structures of FeO ₄ ^2? , RuO₄, RuO ₄ ^? , RuO ₄ ^2? and OsO₄ have been investigated using the Hartree-Fock-Slater Discrete Variational Method. The calculated ordering of the valence orbitals is 2t ₂, 1e, 2a ₁, 3t ₂ andt ₁ with thet ₁ orbital as the highest occupied. The first five charge transfer bands are assigned as:t ₁→2e(v ₁), 3t ₂→2e(v ₂),t ₁→4t ₂(v ₃), 3t ₂→4t ₂(v ₄) and 2a ₁→4t ₂(v ₅). It is suggested that ad-d transition should be observed at 1.5 eV in RuO ₄ ^? and RuO ₄ ^2? .     

Phase equilibria in the Tl2MoO4-Nd2(MoO4)3-Hf(MoO4)2 system and the crystal structure of double molybdate TlNd(MoO4)2

The Tl₂MoO₄-Nd₂(MoO₄)₃-Hf(MoO₄)₂ system was studied in the subsolidus region using X-ray powder diffraction. New triple molybdates were found to exist in this system: Tl₅NdHf(MoO₄)₆ (5: 1: 2), TlNdHf_0.5(MoO₄)₃ (1: 1: 1), and Tl₂NdHf₂(MoO₄)_6.5 (2: 1: 4). The first TlNd(MoO₄)₂ single crystals were grown from melt solutions with spontaneous nucleation. Their crystal structure was refined from X-ray diffraction data (Bruker X8 Apex automated diffractometer, MoK _α radiation, 386 F(hkl), R = 0.0136). The tetragonal unit cell parameters are as follows: a = 6.3000(2) Å, c = 9.5188(5) Å, V = 377.80(3) ų, Z = 2, ρ_calcd = 5.876 g/cm³, space group P4/nnc. The structure is a framework built of NdO₈ and TlO₈ tetragonal antiprisms linked via shared lateral edges and alternating in the checkerboard order. Layers share oxygen vertices with MoO₄ interlayer tetrahedra and are linked into the framework.     

Structural and transport properties of compounds in the CsHSO4-KH2PO4 system with a high potassium dihydrophosphate content

The (1?x)CsHSO₄-xKH₂PO₄ system was studied in a wide range of compositions (x = 0.05?0.97). Mixed salts with different crystal structures and different transport, thermodynamic, and thermal properties were shown to form. In these mixed (1?x)CsHSO₄-xKH₂PO₄ compounds (x = 0.05?0.5), solid solutions formed on the basis of the compound with a crystal structure Cs₃(HSO₄)₂(H₂PO₄) (C2/c). As the content of KH₂PO₄ increased further, another compound with a crystal structure, CsH₅(PO₄)₂ (P2₁/c), formed and existed up to x = 0.95. At x ≥ 0.7, KH₂PO₄ existed as an individual phase along with CsH₅(PO₄)₂; its content increased considerably at x ≥ 0.9. The low conductivities and high activation energies of (1?x)CsHSO₄-xKH₂PO₄ at x = 0.6?0.95 were close to those for CsH₅(PO₄)₂. The compounds with x = 0.5–0.9 showed low thermal stability corresponding to the individual CsH₅(PO₄)₂ phase.     

Group IB organometallic chemistry: XXIX. Synthetic and structural aspects of polynuclear arylcopperlithium compounds Ar4Cu2Li2 (“arylcuprates”) and interaggregate exchange phenomena in Ar4Cu4/Ar4Li4/Ar4Cu2Li2 systems

The thermally stable arylmetal-IB-lithium compounds (2-Me₂NCHZC₆H₄)₄M₂Li₂ (M = Cu, Ag or Au; Z = H or Me) and (2-Me₂NC₆H₄)₄M₂Li₂ have been prepared by a $\text{2}\text{1}$ molar reaction of the aryllithium compounds with the corresponding metal-IB halide (Cu or Ag) or metal-lB halide phosphine complex (BrAuPPh₃). These tetranuclear complexes were also made by an interaggregate exchange reaction of the pure arylmetal-IB clusters with the aryllithium compound.The structure of these compounds in solution consists of aryl groups bridging one metal-lB and one lithium atom of a trans M₂Li₂ core. The four built-in ligands coordinate to lithium resulting in two-coordination at M and four-coordination at Li. These conclusions were based on ¹H and ¹³C NMR spectroscopic data (J(AgC(1)), J(LiC(1)) of solutions of these tetranuclear compounds as well as on the ¹⁹⁷Au Mössbauer data of solid (2-Me₂NC₆H₄)₄Au₂Li₂ (IS 5.65 mm/s and QS 12.01 mm/s).The interaggregate exchange between the tetranuclear species is discussed in terms of an associative mechanism involving formation of an octanuclear intermediate in which the aryl groups can migrate via (3c-2e)edge-(2c-2e)corner(3c-2e)edge movements without M₂Ar bond cleavage.Some aspects of the organic reactions in which organocuprates are involved as intermediates are discussed in terms of the novel structural information.     

Oxyfluorinated compounds with an open structure XVI. Synthesis,structure determination and magnetic properties of Fe4F3(PO4)(HPO4)4(H2O)4(N2C3H12) [ULM-15]

Fe₄F₃(PO₄)(HPO₄)₄(H₂O)₄(N₂C₃H₁₂) (labelled ULM-15) was prepared hydrothermally (7 days, 453 K, autogenous pressure) in the presence of 1,3-diaminopropane as organic template. Its structure was determined by single crystal X-ray diffraction. ULM-15 is monoclinic (Space group C2/c (no 15)) with lattice parameters a = 24.176(1) , b = 14.558(1) , c = 7.186(1) , β = 102.3(1)°, V = 2470.8(3) ³, Z = 4. Its three-dimensional framework is constituted from corner-sharing FeX₆ (X = O, F, H₂O) octahedra and tetrahedral PO₄ and HPO₄ groups. The structure presents trans-chains of FeO₄F₂ octahedra related to ferric dimers [Fe₂O₈F₂(H₂O)₂] by tetrahedral units. They delimit 16-membered rings channels along [001] in which the diprotonated amines are inserted. ULM-15 shows 3D antiferromagnetic behaviour below T_N ≈ 22 K.     

Determination of phase fields in the CsBr-Cs2ZnBr4-Cs2CdBr4-Cs2HgBr4 quaternary system

Phase equilibria in the CsBr-Cs₂ZnBr₄-Cs₂CdBr₄-Cs₂HgBr₄ quaternary system were studied by differential thermal analysis. The CsBr-Cs₂ZnBr₄-Cs₂HgBr₄ ternary system has a ternary eutectic, E ₁, at ～83 mol % Cs₂HgBr₄, 2 mol % Cs₂ZnBr₄, and 15 mol % CsBr with a melting point of ～415°C. The CsBr-Cs₂ZnBr₄-Cs₂CdBr₄ ternary system has a ternary eutectic, E ₂, at ～53.5 mol % Cs₂CdBr₄, 1.5 mol % Cs₂ZnBr₄, and 45 mol % CsBr with a melting point of ～450°C. The polythermal section Cs₃ZnBr₅-Cs₂CdBr₄-Cs₂HgBr₄ in the CsBr-Cs₂ZnBr₄-Cs₂CdBr₄-Cs₂HgBr₄ quaternary system was constructed and investigated. This section is a quasi-ternary system and is characterized by the formation of regions of solid solutions Cs₂Zn _x Cd _y Hg_{1?x ? y} Br₄ and solid solutions based on Cs₃ZnBr₅. The liquidus surface of the quaternary system consists of three fields of primary crystallization of cesium bromide, a solid solution Cs₂Zn _x Cd _y Hg_{1?x ? y} Br₄, and a solid solution based on Cs₃ZnBr₅.     

Syntheses and single-crystal structures of CsTh(MoO4)2Cl and Na4Th(WO4)4

Colorless crystals of CsTh(MoO₄)₂Cl and Na₄Th(WO₄)₄ have been synthesized at 993 K by the solid-state reactions of ThO₂, MoO₃, CsCl, and ThCl₄ with Na₂WO₄. Both compounds have been characterized by the single-crystal X-ray diffraction. The structure of CsTh(MoO₄)₂Cl is orthorhombic, consisting of two adjacent [Th(MoO₄)₂] layers separated by an ionic CsCl sublattice. It can be considered as an insertion compound of Th(MoO₄)₂ and reformulated as Th(MoO₄)₂·CsCl. The Th atom coordinates to seven monodentate MoO₄ tetrahedra and one Cl atom in a highly distorted square antiprism. Na₄Th(WO₄)₄ adopts a scheelite superlattice structure. The three-dimensional framework of Na₄Th(WO₄)₄ is constructed from corner-sharing ThO₈ square antiprisms and WO₄ tetrahedra. The space within the channels is filled by six-coordinate Na ions. Crystal data: CsTh(MoO₄)₂Cl, monoclinic, P2₁/c, Z=4, a=10.170(1) Å, b=10.030(1) Å, c=9.649(1) Å, β=95.671(2)°, V=979.5(2) Å³, R(F)=2.65% for I>2σ(I); Na₄Th(WO₄)₄, tetragonal, I4₁/a, Z=4, a=11.437(1) Å, c=11.833(2) Å, V=1547.7(4) Å³, R(F)=3.02% for I>2σ(I).     

Preparation of 4-nitrostyrene

The interaction of D,L-1-(4-nitrophenyl)ethanol with SOCl₂ and P₄O₁₀ has been studied. In the reaction of D,L-1-(4-nitrophenyl)ethanol with SOCl₂ a mixture of 1-(4-nitrophenyl)-1-chloroethane, 1,1′-bis-(4-nitrophenyl)diethyl ether, and 4-nitrostyrene (yield 21%) has been formed. The direction of reaction of D,L-1-(4-nitrophenyl)ethanol with P₄O₁₀ in toluene has been affected significantly by the order of reagents addition and the solution concentration. 4-Nitrostyrene has been obtained in the only case: the addition of P₄O₁₀ to diluted solution of D,L-1-(4-nitrophenyl)ethanol and subsequent refluxing. Also the procedure of 4-nitrostyrene preparation via the cleavage of 2-(4-nitrophenyl)ethyl nitrate with alkoxy anion in the alcoholic solution has been upgraded.     

Synthesis,crystal structure,and magnetic properties of K4Mn3(HPO4)4(H2PO4)2

A new layered compound, K₄Mn₃(HPO₄)₄(H₂PO₄)₂ (1), has been synthesized under hydrothermal conditions. It crystallizes in the monoclinic space group P2₁/n with a = 8.874(2) Å, b = 6.554(1) Å, c = 18.075(4) Å, and β = 93.39(3)°. The structure consists of zigzag [Mn₃O₁₄]_n chains of edge-sharing MnO₆ octahedrons and MnO₇ pentagonal bi-pyramids, which form layers of formula [Mn₃(HPO₄)₄(H₂PO₄)₂]^4? in the ab plane via H₂PO₄ and HPO₄ units with vertex-sharing. Potassium ions lie between these layers. Magnetic measurements indicate Curie–Weiss behavior above 6 K for 1. A Heisenberg model, with alternating exchange interactions J₁J₁J₂… within the chain and exchange interactions J₃J₃… between the chains, is proposed to describe the magnetic behavior.     

Synthesis and structures of two hydrazone compounds derived from 4-methylbenzohydrazide

Two hydrazone compounds N′-(2,4-dichlorobenzylidene)-4-methylbenzohydrazide monohydrate (1) and 2-chloro-5-nitro-N′-(4-methylbenzylidene)benzohydrazide (2) derived from 4-methylbenzohydrazide with different benzaldehydes are synthesized and characterized by physicochemical methods and single crystal X-ray diffraction. Compound 1 crystallizes in the orthorhombic space group P2₁2₁2₁ with unit cell parameters a = 4.714(2) Å, b = 13.093(3) Å, c = 24.754(3) Å, V = 1527.9(8) ų, Z = 4, R ₁ = 0.0812, and wR ₂ = 0.1623. Compound 2 crystallizes in the monoclinic space group Cc with unit cell parameters a = 11.564(2) Å, b = 13.271(2) Å, c = 9.462(2) Å, β = 96.860(2)°, V = 1441.7(4) ų, Z = 4, R ₁ = 0.0461, and wR ₂ = 0.0896. The crystals of the compounds are stabilized by intermolecular hydrogen bonds as well as π…π stacking interactions.     

A CNDO-MO calculation of VCl4

The electronic structure of the tetrahedral molecule VCL₄ is investigated within the CNDO-MO approximations. The metal and ligand valence orbitals, 3d, 4s, 4p; and 3s, 3p; respectively, have been systematically varied in an attempt to minimize the total energy; “optimum” V 4s(χ₄ = 1.10) and 4p(d ³ p ²) orbitals have been established, but V 3d(d ⁿ ) and Cl(-δ) valence orbitals are only seen to favor lower energy for expanded orbitals. Since determining the one-electron molecular orbital level which is occupied by the vanadium lone electron is a major aspect of this investigation, all calculations have been performed in triplicate: calculations assuming the unpaired electron occupies the 3a ₁, 2 _e and 4t ₂ molecular orbital (ground state electronic configurations² A ₁,² E, and² T ₂, respectively). The Hartree-Fock equations have been solved by Roothaan's SCF method for open shells, but off-diagonal multipliers between filled and partly filled molecular orbitals of the same symmetry have been neglected. As a qualitative estimate of the error introduced by this simplification, the pertinent overlap integrals between the eigenfunctions from calculations for the three possible configurations,² A ₁,² E, and² T ₂, are investigated as functions of the component 3d(d ⁿ ) and Cl(-δ) valence orbitals. The overlap integrals from the relevant² A ₁ and² T ₂ calculations are reasonably small, but the neglect of off-diagonal multipliers in calculations on the² E state is found to be a poor approximation. An ordering of the non-filled molecular orbitals in VCl₄ of 4t ₂ < 3a ₁ < 2e < 5t ₂ seems most consistent with the numerous calculations. This suggested ground state electronic configuration of² T ₂ introduces new aspects to the consideration of a (dynamic) Jahn-Teller effect in VCl₄. Experimental data pertinent to the electronic structure of VCl₄ has been briefly summarized, but unfortunately it is inadequate to confirm or deny the present calculations.     

Crystal Structures of Hydrochlorides of 2,3-Pentamethylene-3, 4-dihydroquinazolin-4-one

The crystal structures of hydrate (1) and anhydrate (2) forms of 2,3-pentamethylene-3,4-dihydroquinazolin-4-one hydrochloride have been determined by X-ray structure analysis. Crystal data of 1 are 2(C₁₃H₁₄N₂O)*3(HCl)*4.5 (H₂O), triclinic P?1, Z=2, a=8.004(5), b=13.129(7), c=15.725(7) Å, α=106.45(4), β=92.61(4), γ=97.98(5), R=0.0652 and 2 are C₁₃H₁₄N₂O*HCl, monoclinic C2/c, Z=8, a=21.360(4), b=5.954(1), c=21.263(4), β=117.89(3), R=0.0556. The crystal of the hydrate form 1is unstable. This form collapses easily with evaporation of H₂O and part of HCl molecules from crystals. By recrystallizing destroyed form has been obtained stable crystal form 2.     

Rhodium catalyzed hydroacylation of ethylene with 4-pentenals. reactions of 4-hexenal-1-d

A catalyst derived from 2,4-pentanedionatobis(ethylene)rhodium(I), I, promoted the addition of 4-pentenal to ethylene. The reaction was accompanied by the formation of double bond migration products derived from the 4-pentenal reactant and from the 6-hepten-3-one primary product. Compound I accomplished the addition of 4-hexenal to ethylene to afford high yields of 6-octen-3-one. The fate of the aldehyde hydrogen in this transformation has been determined in experiments employing 4-hexenal-1-d as reactant. Treatment of 4-hexenal-1-d with I in CHCl₃ and CDCl₃ afforded 6-octen-3-one possessing >50% d_o molecules while the isotopic composition of recovered unexpended 4-hexenal remained >96% d₁. 6-Octen-3-one products with isotopic compositions of >66% d_o were afforded when ethylene was introduced to reaction mixtures. The location of deuterium in 6-octen-3-one, derived from treatment of 4-hexenal-1-d with I in the absence of added C₂H₄, was determined to be distributed at C-1 and C-2 and at the CC bond by analysis of the ¹H and ²H NMR spectra. Unexpended ethylene was recovered and was found to contain a substantial amount of deuterium. Mechanistic implications of these results are discussed.     

Behavior of Co4+ ion in K2NiF4-type (Ca1+xSm1−x)CoO4

Orthorhombic K₂NiF₄-type (Ca_1+xSm_1−x)CoO₄ (0.00 ≤ x ≤0.15) with space group Bmab has been synthesized by the polymerized complex route. The cell parameters (a and b) decrease, while the cell parameter (c) increases with increasing Co⁴⁺ ion content. The global instability index (GII) indicates that the crystal stability of (Ca_1+xSm_1−x)CoO₄ is not influenced by the Co⁴⁺ ion content. (Ca_1+xSm_1−x)CoO₄ is a p-type semiconductor and exhibits hopping conductivity in the small-polaron model at low temperatures. The magnetic measurement indicates that (Ca_1+xSm_1−x)CoO₄ shows paramagnetic behavior above 5 K, and that the spin state of both the Co³⁺ and Co⁴⁺ ions is low. The Co⁴⁺ ion acts as an acceptor, and the electron transfer becomes active through the Co³⁺–O–Co⁴⁺ path as the Co⁴⁺ ions increase.     

Homogeneity regions of double molybdates in the Na2MoO4-MgMoO4 system and structures of triclinic Na1.51Mg2.245(MoO4)3 and Na1.66Mn2.17(MoO4)3

In the samples of the Na₂MoO₄-MgMoO₄ system quenched in the air at above 600°C, by powder X-ray diffraction two double molybdates of variable composition are detected: monoclinic alluaudite-like Na_4?2x Mg_1+x (MoO₄)₃ (0.05 ≤ x ≤ 0.35) and triclinic Na_2?2y Mg_2+y (MoO₄)₃ (0.10 ≤ y ≤ 0.40) isostructural to previously studied Na₂Mg₅(MoO₄)₆. Sodium-magnesium molybdate of the Li₃Fe(MoO₄)₃ structure type is not revealed in this system. By spontaneous flux crystallization, the crystals are obtained and the structures of two triclinic double molybdates of the Na₂Mg₅(MoO₄)₆ structure type (space group $P\bar 1$ , Z = 1) containing magnesium and manganese are determined. The results of the refinement of site occupancies made it possible to determine the composition of the studied crystals: for the compound with magnesium (Na)_0.5(Na_0.255□_0.745)(Na_0.755Mg_0.245)Mg₂(MoO₄)₃ or Na_1.51Mg_2.245(MoO₄)₃ (a = 6.9577(1) Å, b = 8.6330(2) Å, c = 10.2571(2) Å, α = 106.933(1)°, β = 104.864(1)°, γ = 103.453(1)°, R = 0.0188); for the compound with manganese (Na)_0.5(Na_0.33□_0.67)(Na_0.83Mn_0.17)Mn₂(MoO₄)₃ or Na_1.64Mn_2.17(MoO₄)₃ (a = 7.0778(2) Å, b = 8.8115(2) Å, c = 10.4256(2) Å, α = 106.521(1)°, β = 105.639(3)°, Γ = 103.233(1)°, R = 0.0175). The Na₂Mg₅(MoO₄)₆ structure is redetermined and it is shown that actually it corresponds to the composition Na_1.40Mg_2.30(MoO₄)₃.     

Phase equilibrium in the Cs2MoO4-Bi2(MoO4)3-Zn(MoO4)2 system and the crystal structure of new triple molybdate Cs5BiZr(MoO4)6

The subsolidus region of the Cs₂MoO₄-Bi₂(MoO₄)₃-Zr(MoO₄) system was studied by X-ray powder diffraction. Quasi-binary sections were elucidated, and triangulation performed. Triple molybdates with the component ratios 5: 1: 2 (S ₁) and 2: 1: 4 (S ₂) were prepared for the first time. Crystals of cesium bismuth zirconium molybdate of the 5: 1: 2 stoichiometry (Cs₅BiZr(MoO₄)₆) were grown from fluxed melts with spontaneous nucleation. The composition and crystal structure of this triple molybdate were refined using X-ray diffraction data (collected on X8 APEX automated diffractometer, MoK _α radiation, 2348 F(hkl), R = 0.0226). The trigonal unit cell parameters were as follows: a = b = 10.9569(2), c = 39.804(4) Å, V = 4138.4(4) ų, Z = 6, space group R $ \bar 3 The subsolidus region of the Cs₂MoO₄-Bi₂(MoO₄)₃-Zr(MoO₄) system was studied by X-ray powder diffraction. Quasi-binary sections were elucidated, and triangulation performed. Triple molybdates with the component ratios 5: 1: 2 (S ₁) and 2: 1: 4 (S ₂) were prepared for the first time. Crystals of cesium bismuth zirconium molybdate of the 5: 1: 2 stoichiometry (Cs₅BiZr(MoO₄)₆) were grown from fluxed melts with spontaneous nucleation. The composition and crystal structure of this triple molybdate were refined using X-ray diffraction data (collected on X8 APEX automated diffractometer, MoK _α radiation, 2348 F(hkl), R = 0.0226). The trigonal unit cell parameters were as follows: a = b = 10.9569(2), c = 39.804(4) ?, V = 4138.4(4) ?³, Z = 6, space group R c. The mixed-metal three-dimensional framework in this structure is built of Mo tetrahedra and two sorts of (Bi,Zr)O₆ octahedra. Large interstices accommodate two sorts of cesium atoms. The Bi³⁺ and Zr⁴⁺ cation distributions over two positions were refined during structure solution. Original Russian Text ? B.G. Bazarov, T.V. Namsaraeva, R.F. Klevtsova, A.G. Anshits, T.A. Vereshchagina, R.V. Kurbatov, L.A. Glinskaya, K.N. Fedorov, Zh.G. Bazarova, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 9, pp. 1585–1589.     

Resonance Raman spectrum of the complex [(C2H5)4N] AuBr4

A resonance Raman spectrum of the complex [(C₂H₅)₄N] AuBr₄ has been observed by use of 457.9 nm Ar⁺ excitation. Three progressions in the totally symmetric stretching fundamental ν₁ (a_1g) have been observed, viz. nν₁ (as far as n = 9), ν₂ + nν₁ (as far as n = 1), and ν₄ + nν₁ (as far as n = 6). The spectroscopic constants ω₁ and x₁₁ have been determined from an analysis of the nν₁ and ν₄ + nν₁ progressions.     

Phase equilibria in the systems Rb2MoO4-R2(MoO4)3-Hf(MoO4)2 (R = Al, In, Sc, Fe(III)) and the crystal structure of double molybdate RbFe(MoO4)2

The systems Rb₂MoO₄-R₂(MoO₄)₃-Hf(MoO₄)₂ have been investigated in the subsolidus region by X-ray powder diffraction, DTA, and IR spectroscopy. Triple molybdates of the composition 5: 1: 2 are formed in the systems with R = Al, In, Sc, and Fe. Molybdates of composition 5: 1: 3 and 1: 1: 1 are found in the iron(III)-containing system in addition to the 5: 1: 2 molybdate. Single crystals of the double molybdate RbFe(MoO₄)₂, which is formed in the Rb₂MoO₄-Fe₂(MoO₄)₃ system, have been grown. The structure of this double molybdate has been refined using X-ray diffraction data (X8 APEX automated diffractometer, MoK _α radiation, 373 F(hkl), R = 0.0287). The trigonal unit cell parameters are the following: a = b = 5.6655(2) Å, c = 7.5061(4) Å, V = 208.65(1) ų, Z = 1, ρ_calc = 3.670 g/cm³, space group R3m1. The structure is formed by layers of FeO₆ octahedra sharing corners with MoO₄ tetrahedra and RbO₁₂ icosahedra.     

Phase formation in the Ag2MoO4-CoMoO4-Al2(MoO4)3 system

The subsolidus region of the Ag₂MoO₄-CoMoO₄-Al₂(MoO₄)₃ ternary salt system was studied by X-ray powder diffraction analysis. New compounds Ag_1?x Co_1?x Al_{1 + x} (MoO₄)₃ (0 ≤ x ≤ 0.4) and AgCo₃Al(MoO₄)₅ were detected to form. The variable-composition phase Ag_1?x Co_1?x Al_{1 + x} (MoO₄)₃ is of the NASICON structure type (space group \(R\bar 3c\) ). AgCo₃Al(MoO₄)₅ crystallizes in the triclinic symmetry (space group \(P\bar 1\) Z = 2) with the unit cell parameters a = 6.9101(6), b = 17.519(1), c = 6.8241(6) Å, α = 87.356(7)°, β = 101.078(7)°, and γ = 91.985(9)°. The compounds are thermally stable until 770–780 and 760°C, respectively.     

Phase relations in the systems M2MoO4-Cr2(MoO4)3-Zr(MoO4)2 (M = Li, Na, or Rb)

Phase equilibria in the systems M₂MoO₄-Cr₂(MoO₄)₃-Zr(MoO₄)₂ (M = Li, Na, or Rb) were investigated by X-ray powder diffraction analysis, DTA, and IR spectroscopy. The subsolidus structure of the phase diagrams of the systems under study was established. Two phases are formed in the Rb₂MoO₄-Cr₂(MoO₄)₃-Zr(MoO₄)₂ system with the molar ratios of the starting components equal to 5: 1: 1 (S ₂) and 1: 1: 1 (S ₁). Proceeding from that the isostructurality of Rb₅FeHf(MoO₄)₆ and S ₂ the unit cell, parameters are determined for S ₂.