Crystal structure, electronic structure and physical properties of the new low-valent thallium silicon telluride Tl6Si2Te6 in comparison to Tl6Ge2Te6

The title compounds were prepared from the elements in the stoichiometric ratio at 800 °C under exclusion of air. Tl₆Si₂Te₆ crystallizes in the space group P1¯, isostructural with Tl₆Ge₂Te₆, with , , , α=89.158(2)°, β=96.544(2)°, γ=100.685(2)°, (Z=2). Its structure is composed of dimeric [Si₂Te₆]⁶⁻ units with a Si-Si single bond, while the Tl atoms are irregularly coordinated by five to six Te atoms. Numerous weakly bonding Tl-Tl contacts exist. Both title compounds are black semiconductors with small band gaps, calculated to be 0.9 eV for Tl₆Si₂Te₆ and 0.5 eV for Tl₆Ge₂Te₆. The Seebeck coefficients are +65 μV K⁻¹ in case of Tl₆Si₂Te₆ and +150 μV K⁻¹ in case of Tl₆Ge₂Te₆ at 300 K, and the electrical conductivities are 5.5 and 3 Ω⁻¹ cm⁻¹, respectively.     

[As(V)As(III)O6]: An uncommon anion group in the crystal structure of K2Cu3(As2O6)2

The crystal structure of K₂Cu₃(As₂O₆)₂ was determined from single-crystal X-ray data by a direct method strategy and Fourier summations [a = 10.359(4) Å, B = 5.388(2)Å, C = 11.234(4) Å, β = 110.48(2)°; space group C2/m; Z = 2; R_w = 0.025 for 1199 reflections up to sin /λ = 0.81 Å⁻¹]. In detail, the structure consists of As(V)O₄ tetrahedra and As(III)O₃ pyramids linked by a common O corner atom to [As(V)As(III)O₆]⁴⁻ groups with symmetry m. The bridging bonds As(V)---O [1.749(3) Å] and As(III)---O [1.838(2) Å] are definitely longer than the other As(V)---O bonds [mean 1.669 Å] and As(III)---O bonds [1.764(2) Å, 2×]. The angle As(V)---O---As(III) is 123.0(1)°. The Cu atoms are [4 + 2]- and [4 + 1]-, and the K atom is [9]-coordinated to oxygen atoms. The As₂O₆ groups and the Cu coordination polyhedra are linked to sheets parallel to (001). These sheets are connected by the K atoms. Single crystals of K₂Cu₃(As₂O₆)₂ suitable for X-ray work were synthesized under hydrothermal conditions.     

On the crystal structure of the germanium-based cationic clathrates [Ge38.3Sb7.7]I7.44, [Ge38.1P7.9]I8, and [Ge30.5Sn7.7P7.75]I7.88

Compounds [Ge_38.3Sb_7.7]I_7.44, [Ge_38.1P_7.9]I₈, and [Ge_30.5Sn_7.7P_7.75]I_7.88 with the clathrate type-I structure were synthesized. They crystallize in the cubic space group Pm[`3]nPm\bar 3n with the unit cell parameter a = 10.8592(9), 10.4983(12), and 10.7210(10) ? (Z = 1), respectively. Their crystal structure represents the germanium(tin)-pnictogen framework, capturing the guest iodine anions in its cavities. All compounds have no vacancies in the host substructure; however, two of them show vacancies in the guest positions. The atomic distribution over the framework sites is of the most interest as it follows trends associated with the relative electronegativities of the atoms composing the framework. The results of the band structure calculations and application of the Zintl counting scheme are also discussed in relation to potential thermoelectric properties.     

Synthesis of 1,2-ethanediylbis(diphenyl-phosphonium)-PH,P′H′ hexachloromolybdate(III) I and nonachlorodimolybdate(III) II. The crystal structure of (dppeH2)3[MoCl6]2·12h2O

Two compounds of the formulae (dppeH₂)₃[MOCl₆]₂ ·12H₂O I and (dppeH₂)₃[Mo₂Cl₉]₂II are described. For compound I, which proved to be active in olefin epoxidation, the crystal structure was determined. The rose-pink crystals are triclinic, space group P$\text{1}$ with a = 13.715(9), b₃ = 14.686(7), c = 12.512(7) Å, α = 109.56(4), β = 97,98(4) and γ = 91.27(5)°, V = 2345 Å, D_m = 1.42 and D_c = 1.44 gcm^?3, Z = 1. Block-diagonal least squares refinement of the structure has led to a final value of the conventional R factor of 0.049 for the 3914 independent reflections with I > 3σ(I). Bond distances are in the range: MoCl 2.439(2)–2.469(2) Å, and PC 1.771(9)–1.806(8) Å.     

Synthesis and crystal structure of the heteroleptic lanthanum(III) bis-diphosphinomethanide complex [La{CH(PPh2)2}2(I)(THF)2]

Treatment of CH₂(PPh₂)₂ with n-BuLi/t-BuOK in diethyl ether affords the potassium diphosphinomethanide complex [K{CH(PPh₂)₂}(OEt₂)_0.5] (1) in high yield. Metathesis of two equivalents of 1 with LaI₃(THF)₄ yields the heteroleptic bis-diphosphinomethanide complex [La{CH(PPh₂)₂}₂(I)(THF)₂] (2). X-ray crystallography shows the diphosphinomethanide ligands in 2 adopt different coordination modes in the solid state; one adopts a κ²-PP mode with no La-C contact, and the other adopts an η³-PCP mode, thus giving an eight-coordinate lanthanum centre.     

Polymorphisme du sulfate de thallium(I), Tl2SO4

X-Ray and DTA techniques were employed to study the thermal and structural characteristics of thallium(I) sulfate. By means of heat treatment, it has been found to evolve successively from a γ-monoclinic phase, through four (β₁, β₂, β₃, β₄) orthorhombic phases to an α-trigonal phase. According to the preparation method at room temperature, this compound can be obtained in γ or β₁ or β₂ form or in a mixture of these three phases. The predominance of one of these three forms and the reversibility of some modifications are strongly influenced by crystal size.     

Synthesis and x-ray crystal structure of [PPN]+2[RuIr4(CO)9(μ2-CO)6]2-

The dianion [RuIr₄(CO)₁₅]^2- has been obtained by reductive carbonylation of mixtures of Ir₄(CO)₁₂ and RuCl₃ · χ H²O, and the bis(triphenylphosphine)-iminium salt has been characterized by single-crystal X-ray diffraction techniques. Crystal data: [((C₆H₅)₃P)₂N]₂[RuIr₄(CO)₁₅], space group P$\text{1}$ (Z  2), a  11.425(3), b  14.141(2), c  25.979(5) Å, α  84.55(1), β  83.53(2), γ  80.71(2)°. The mixed-metal cluster has a structure with an elongated trigonal bipyramidal array of metal atoms in which Ru occupies an apical position. The anion is unstable in vacuum or in an N₂ atmosphere yielding predominantly another mixed-metal species which is not as yet fully characterized. Upon reexposure to CO, this latter species is converted back to [RuIr₄(CO)₁₅]^2-, plus additional products.     

Phase equilibria in the Tl2Te-SnTe-Bi2Te3 system

phase equilibria in the Tl₂Te-SnTe-Bi₂Te₃ system were studied by differential thermal analysis (DTA), X-ray powder diffraction, and microhardness measurements. Some polythermal sections and isothermal (at 600 and 800 K) sections of the phase diagram and a projection of the liquidus surface were constructed. It was shown that the system is characterized by the formation of solid solutions with the Tl₅Te₃ structure (δ) and solid solutions based on SnTe (γ₁), Tl₂Te (α), Bi₂Te₃ (β), and two TlBiTe₂ (γ₂ and γ′₂) phases. Their homogeneity regions were determined. The liquidus surface consists of the primary crystallization fields of the β-, γ₁-, γ′₂-, and δ phases and the compounds SnBi₂Te₄ and SnBi₄Te₇. The liquidus of the α phase is degenerate. The primary crystallization fields of phases were determined, and the types and coordinates of in- and monovariant equilibria were found.     

Synthesis and crystal structure of [Re2Cl2(CO)6(S e)]

The dinuclear complex [Re₂Cl₂(CO)₆S e] has been prepared and characterized in the solid state by X-ray crystallography. Proton NMR spectroscopy has shown the structure to be stereochemically rigid in solution.     

The crystal structure of Ca6Eu2Na2(PO4)6F2

The crystal structure of Ca₆Eu₂Na₂(PO₄)₆F₂ has been determined by single crystal X-ray diffraction. The unit cell constants are $\text{a = 9.385(2), c = 6.893(3)}\text{A}\text{?}$ and the space group is $\text{P6}{}_3\text{m}$. The structure was refined by normal full matrix least squares techniques. The final value of the refinement indicator is R = 0.065, based on 419 reflections.The structure of Ca₆Eu₂Na₂(PO₄)₆F₂ contains disordered cations in both the triangle and column positions. The occupation of the six triangle sites is $\text{1}\text{4}\text{Eu}$ and $\text{3}\text{4}\text{Ca}$ and of the four column sites $\text{1}\text{2}\text{Na}\text{,}\text{4}\text{10}\text{Ca}$, and $\text{1}\text{10}\text{Eu}$.     

New thallium iodates—Synthesis, characterization, and calculations of Tl(IO3)3 and Tl4(IO3)6, [Tl3Tl(IO3)6]

Two new thallium iodates have been synthesized, Tl(IO₃)₃ and Tl₄(IO₃)₆ [Tl⁺₃Tl³⁺(IO₃)₆], and characterized by single-crystal X-ray diffraction. Both materials were synthesized as phase-pure compounds through hydrothermal techniques using Tl₂CO₃ and HIO₃ as reagents. The materials crystallize in space groups R-3 (Tl(IO₃)₃) and P-1 (Tl₄(IO₃)₆). Although lone-pairs are observed for both I⁵⁺ and Tl⁺, electronic structure calculations indicate the lone-pair on I⁵⁺ is stereo-active, whereas the lone-pair on Tl⁺ is inert.     

The crystal structure of the cation-disordered phase (Tl0.75Pb0.25)4Cl5

The 3 : 1 compound in the TlClPbCl₂ system crystallizes in the noncentrosymmetric space group P4₁2₁2 (D₄⁴) or its enantiomorph P4₃2₁2 D₄⁶). Lattice constants are a = 8.450(1)Å and c = 14.927(1)Å. Single-crystal X-ray diffraction data were collected using AgKα radiation. The structure was determined by analysis of Patterson and difference Fourier syntheses. Least-squares refinement of 41 parameters with 402 unique data converged with R_w = 0.036. In the structure the 12 Tl(I) and 4 Pb(II) ions are disordered over two eightfold sites. The formula is therefore appropriately written as (Tl_0.75Pb_0.25)₄Cl₅. A difference in size of the two positions suggests a preferential concentration of Pb(II) in the smaller site. The disordering of aliovalent cations together with a three-dimensional network of face-sharing polyhedra of cations surrounding the anions of the structure suggests (Tl_0.75Pb_0.25)₄Cl₅ as a particularly favorable case for enhancement of chloride ion conductivity by doping with TlCl. Irregularities in the coordination polyhedra about the cations can be explained by the presence of stereochemically active lone-pair electrons of the cations. The structure of (Tl_0.75Pb_0.25)₄Cl₅ is similar to that of the alloy Zr₅Si₄.     

The crystal structure of hydrogen cerium(III) sulfate hydrate, [H3O][Ce(SO4)2] · H2O

[H₃O][Ce(SO₄)₂] · H₂O crystallizes in the monoclinic system with unit-cell dimensions (from single-crystal data) a = 9.359(4), b = 9.926(4), c = 8.444(3) Å, β = 96.53(9)° and space group P2₁/n, z = 4. The structure was solved by conventional heavy-atom methods using 1787 counter-measured reflections (MoKα radiation), and refined using full-matrix least-squares techniques to an R of 0.0465 (ωR = 0.0413). The structure consists of cerium(III) ions in irregular nine-coordination to oxygen atoms from two bidentate sulfate ions, four monodentate sulfate oxygen atoms, and one water molecule. The oxonium ions are present as isolated ions in the structure and take par in the hydrogen bonding network. The Ce-O bond lengths range from 2.454(7) to 2.626(6) Å.     

The crystal structure of a complex cerium(III) molybdate; Ce6(MoO4)8(Mo2O7)

Ce₆Mo₁₀O₃₉ crystallizes in the triclinic system with unit-cell dimensions (from single-crystal data) a = 10.148(5), Å, b = 18.764(6), Å, c = 9.566(5), Å, α = 103.12(7)°, β = 78.07(7)°, γ = 107.69(7)°, and space group $\text{P}\text{1}\text{, z = 2}$. The structure was solved using direct methods with 3113 countermeasured reflections (MoKα radiation), and refined using Fourier and least-squares techniques to a conventional R of 0.039 (ωR = 0.047). Ce₆Mo₁₀O₃₉ has a structure that consists of isolated MoO₄ tetrahedra together with one corner-shared pair of tetrahedra, linked to irregular eight-coordinate Ce(III) polyhedra. The average MoO distance of 1.77 Å, and average CeO distance of 2.52 Å are in good agreement with previously reported values.     

Synthesis and crystal structure of gallosilicate- and aluminogermanate tetrahydroborate sodalites Na8[GaSiO4]6(BH4)2 and Na8[AlGeO4]6(BH4)2

Tetrahydroborate enclathrated sodalites with gallosilicate and aluminogermanate host framework were synthesized under mild hydrothermal conditions and characterized by X-ray powder diffraction and IR spectroscopy. Crystal structures were refined in the space group P-43n from X-ray powder data using the Rietveld method. Na₈[GaSiO₄]₆(BH₄)₂: a=895.90(1) pm, V=0.71909(3)×10⁻⁶ nm³, R_P=0.074, R_B=0.022, Na₈[AlGeO₄]₆(BH₄)₂: a=905.89(2) pm, V=0.74340(6)×10⁻⁶ nm³, R_P=0.082, R_B=0.026. The tetrahedral framework T-atoms are completely ordered in each case and the boron atoms are located at the centre of the sodalite cages. The hydrogen atoms of the enclathrated anions were refined on x, x, x positions, restraining them to boron-hydrogen distances of 116.8 pm as found in NaBD₄.The IR-absorption spectra of the novel phases show the typical bands of the tetrahedral group as found in the spectrum of pure sodium boron hydride.The new sodalites are discussed as interesting -containing model compounds which could release pure hydrogen.     

The structure type of Re2Te5, a new [M6X14] cluster compound

Re₂Te₅ crystallizes in a new structure type, having space group Pbca (No. 61) with a = 13.003(5), b = 12.935(7), c = 14.212(5) Å, Z = 12. All atoms are in the general positions 8(c), apart from one Te atom which occupies the special position 4(a) in a center of symmetry. The Re atoms are arranged in octahedral [Re₆] clusters and all the atoms in general positions can be grouped as {[Re₆Te₈]Te₆} complexes. The centers of these units and the Te atom in 4(a) are arranged like a slightly distorted rock salt structure. The Te atoms can be replaced by Se atoms up to at least 40%. Re₂Te₅ and Re₂Se₂Te₃ reveal a semiconductor-like electric behavior which is accounted for by the chemical bonding.     

Synthesis and crystal structure of Ru-supported tungstoantimonate [Sb2W20Ru2(H2O)2(dmso)6O68]

The first Ru^III-supported tungstoantimonate [Ru^II(bpy)₃]₂[Sb₂W₂₀Ru^III₂(H₂O)₂(dmso)₆O₆₈]·3dmso (bpy=bi-pyridine) (1a) has been successfully isolated as [Ru(bpy)₃]²⁺ (Rubpy) salt by routine synthetic reaction in mixed solutions with dmso and water. Single-crystal X-ray analysis was carried out on 1a, which crystallizes in the triclinic system space group P-1 with a=16.804 (6), b=16.988 (6), c=17.666 (6) Å, α=107.397 (13)°, β=106.883 (13)°, γ=103.616 (12)°. V=4309 (3) Å³, Z=1 with R1=0.0773. The compound 1a reveals the following features: (1) Rubpy is firstly used as an alternative ruthenium-source for the synthesis of Ru-substituted heteropolytungstate; (2) the structure of 1a consists of four Ru^III-O-S(CH₃)₂ and two W-O-S(CH₃)₂ bonds resulting in an assembly with C₂ symmetry; (3) the Ru^III ions are linked to two dmso groups via two Ru^III-O-S(CH₃)₂ bonds, which represents the other dmso-coordination mode to Ru^III in POM chemistry. The cyclic voltammetry studies of 1a in dmso/H₂SO₄ (3/1 v/v) at pH 2.5 medium using the glassy carbon electrode as a working electrode show the respective electrochemical behaviors of the W-centers and the Ru-centers within 1a, which could be separated clearly. In addition, the compound 1a exhibits photoluminescence arising from π*−t_2g ligand-to-metal transition of Rubpy.     

Crystal structure of [Co(N2C2H8)3] [AuBr4]2Br bis(tetrabromoaurate(III))tris(ethylenediamine) cobalt(III) bromide

A double complex salt [Co(N₂C2H₈)₃][AuBr₄]₂Br is obtained and characterized using single crystal X-ray diffraction analysis. The crystallographic data of C₆H₂₄Au₂Br₉CoN₆ are as follows: a = 21.6479(17) ?, b = 14.9085(12) ?, c = 8.2676(7) ?, β = 110.820(2)°, V = 1538.92(12) ?³, C2/c space group, Z = 4, d _x = 3.602 g/cm³. Square planar coordination of the gold atom in the complex anion is completed to a tetragonal pyramid by an additional bromine atom of the adjacent complex anion at the Au... Br distance of 3.677 ?.     

Thermogravimetry of the analytical precipitates M2Pb[Co(NO2)6] AND MPb[Co(NO2)6]

Thermogravimetric studies are reported for analytical precipitates of the types MPb[Co(NO₂)₆] and M₂Pb[Co(NO₂)₆], where M represents the univalent cations NH⁺₄, K⁺, Rb⁺, Cs⁺, and Tl⁺. Compounds of the latter series are consitently more stable to higher temperatures. For either series increasing the radius of M increases thermal stability. Decomposition to temperatures approaching 500°C involves some four separate processes.