Phase equilibria in the BaS-Cu<Subscript>2</Subscript>S-Gd<Subscript>2</Subscript>S<Subscript>3</Subscript> system

Phase equilibria in the BaS-Cu₂S-Gd₂S₃ system have been studied along the 800 K isothermal section and the CuGdS₂-BaS, Cu₂S-BaGdCuS₃, BaGdCuS₃-Gd₂S₃, and BaGdCuS₃-BaGd₂S₄ polythermal sections. Complex sulfide BaGdCuS₃ is formed in the title system; it has an orthorhombic KZrCuSe₃-type structure (space group Cmcm) with the unit cell parameters equal to a = 0.40529(2) nm, b = 1.34831(6) nm, c = 1.02940(5) nm. This sulfide melts congruently at 1685 K. BaGdCuS₃ is in equilibrium with sulfides Cu₂S, BaS, Gd₂S₃, CuGdS₂, BaGd₂S₄, BaCu₄S₃, and BaCu₂S₂ and with compositions in the C₀ solid-solution region of the Cu₂S-Gd₂S₃ system. Eutectics are formed between compounds CuGdS₂ and BaGdCuS₃ at 7.0 mol % BaS and T = 1325 K, between BaGdCuS₃ and BaS at 64.0 mol % BaS and T = 1625 K, between Cu₂S and BaGdCuS₃ at 8.0 mol % BaGdCuS₃ and T = 1125 K, between Gd₂S₃ and BaGdCuS₃ at 64.0 mol % Gd₂S₃ and 1495 K, and between BaGdCuS₃ and BaGd₂S₄ at 35 mol % BaGd₂S₄ and T = 1660 K.     

Sm<Subscript>2</Subscript>S<Subscript>3</Subscript>-Sm<Subscript>2</Subscript>O<Subscript>3</Subscript> phase diagram

The Sm₂S₃-Sm₂O₃ phase diagram was studied by physicochemical methods of analysis from 800 K up to melting. Two oxysulfides are formed in the system: Sm₁₀S₁₄O with tetragonal crystal structure (space group I41/acd; unit cell parameters: a = 1.4860 nm, c = 1.9740 nm; microhardness: H = 4700 MPa; solid decomposition temperature: 1500 K) and Sm₂O₂S with hexagonal structure (space group P-3m1; a = 0.3893 nm, c = 0.6717 nm; H = 4500 MPa; congruent melting temperature: 2370 K). Within the extent of the Sm₂O₂S-based solid solution (61–70 mol % Sm₂O₃) at 1070 K, a singular point appears at the compound composition on property-composition curves. The eutectic coordinates: 23 mol % Sm₂O₃ and 1850 K; 80 mol % Sm₂O₃ and 2290 K.     

Phase equilibria in the systems SrS-Cu<Subscript>2</Subscript>S-Ln<Subscript>2</Subscript>S<Subscript>3</Subscript> (Ln = La or Nd)

Phase equilibria in the systems SrS-Cu₂S-Ln₂S₃ (Ln = La or Nd) have been studied along the isothermal section at 1050 K and vertical sections CuLnS₂-SrS and Cu₂S-SrLnCuS₃, which are partially quasibinary joins. Compounds SrLnCuS₃ with Ln = La or Nd have been synthesized for the first time. They crystallize in orthorhombic space group Pnma, the BaLaCuS₃ structure type, with the following unit cell parameters: for SrLaCuS₃, a = 1.1157(2) nm, b = 0.41003(6) nm, c = 1.1545(2) nm; for SrNdCuS₃, a = 1.1083(1) nm, b = 0.40887(7) nm, c = 1.1477(2) nm. Noticeable homogeneity regions for SrLnCuS₃ are not found. The compounds melt congruently by the reaction SrLnCuS₃ ? SrS + L at 1365 K for SrLaCuS₃ and 1400 K for SrNdCuS₃. The tie-lines at 1050 K in the systems SrS-Cu₂S-Ln₂S₃ radiate from SrLnCuS₃ toward phases SrS, Cu₂S, CuLnS₂, and SrLn₂S₄, lying between the phases CuLnS₂ and compositions from the γ-Ln₂S₃-SrLn₂S₄ solid-solution field. Eutectics are formed between the compounds CuLaS₂ and SrLaCuS₃ at 21.0 mol % SrS, T = 1345 K; between the compounds CuNdS₂ and SrNdCuS₃ at 31.0 mol % SrS, T = 1310 K; and between the phases Cu₂S and SrLnCuS₃ at 14.0 mol % SrLaCuS₃, T = 1075 K and 8.0 mol % SrNdCuS₃, T = 1055 K.     

Crystal structures of <Emphasis Type="Italic">trans</Emphasis>-[Re<Subscript>6</Subscript>S<Subscript>8</Subscript>(CN)<Subscript>2</Subscript>L<Subscript>4</Subscript>] complexes,L = pyridine or 4-methylpyridine

The structures of three novel octahedral rhenium cluster compounds [Re₆S₈(CN)₂(py)₄]·H₂O (1), [Re₆S₈(CN)₂(4-Mepy)₄] (2), [Re₆S₈(CN)₂(4-Mepy)₄]·4-Mepy (3) (py = pyridine, 4-Mepy = 4-methylpyridine) are determined by X-ray crystallography. Crystal data are: C2/m space group, a = 14.813(1) Å, b = 14.772(1) Å, c = 9.2122(6) Å, β = 119.085(2)°, V = 1761.7(2) ų, d _x = 3.318 g/cm³, R = 0.0585 (1); I4₁/amd space group, a = 16.0018(3) Å, c = 14.7186(5) Å, V = 3768.81(16) ų, d _x = 3.169 g/cm³, R = 0.0489 (2); P2₁/c space group, a = 9.0452(4) Å, b = 15.8065(7) Å, c = 15.2951(6) Å, β = 103.700(2)°, V = 2124.57(16) ų, d _x = 2.957 g/cm³, R = 0.0245 (3). Molecular cluster complexes interact via π-π stacking affording 3D frameworks in 1 and 2 and chains in 3.     

Structural chemistry of mercury chalcohalides. III. Crystal structure of Hg<Subscript>3</Subscript>S<Subscript>2</Subscript>Cl<Subscript>1.5</Subscript>Br<Subscript>0.5</Subscript> polymorphs

Single crystals of two new mercury thiohalides of the composition Hg₃S₂Cl_{2? x}Br_x(x = 0.5) have been grown from gas phase and studied by X-ray crystallography. Structure refinement for monoclinic (I) and cubic (II) phases (I: a = 16.841(2) Å, b = 9.128(2) Å, c = 9.435(4) Å; β = 90.080(10)°, V = 1450.3(7) ų, space group _C2/_{m, Z} = 8, _R = 0.0528; II: a = 18.006(2) Å, V = 5837.8(11) ų, space group \(Pm\bar 3n\), Z = 32, R = 0.0503) clearly shows that they are polymorphs of the same composition Hg₃S₂Cl_1.5Br_0.5. The monoclinic modification I is similar to the synthetic phases γ-Hg₃S₂Cl₂, β-Hg₃S₂Br₂, Hg₃Se₂Br₂ and to the analogue of radtkeite mineral, Hg₃S₂ClI. The modification II is isostructural to the synthetic β-Hg₃S₂Cl₂. In both structures, each S atom coordinates three Hg atoms with the formation of pyramidal SHg₃ units (Hg-S 2.37–2.48 Å; HgSHg 93.1–97.5 ). The SHg₃ units are linked through Hg vertices into corrugated layers [Hg₁₂S₈]_∞∞ (I) and isolated cubic groups [Hg₁₂S₈] (II). Similarly to other mercury chalcohalides, the crystal structures are basically determined by the halogen atoms which form a cubic sublattice incorporating the Hg-S moieties.     

A novel metal chalcogenide: HgCd<Subscript>4</Subscript>S<Subscript>5</Subscript>

A novel metal chalcogenide HgCd₄S₅ (1) was synthesized from solid-state reactions and structurally characterized. Compound 1 crystallizes in the space group C222₁ of the orthorhombic system with four formula units in a cell: a = 12.5661(5) Å, b = 7.2551(5) Å, c = 10.7520(7) Å, V = 980.2(1) ų, Cd₄HgS₅, M _r = 810.49, D _c = 5.492 g/cm³, S = 1.010, μ(MoK _α) = 25.128 mm^?1, F(000) = 1408, R = 0.0611 and wR = 0.1495. Compound 1 is characterized by a 3-D cadmium sulfide framework structure with the infinite mercury sulfide chains located in the cavities.     

Synthesis and Physicochemical Properties of a Lanthanum-Containing Analog of the Mineral Berthierite FeSb<Subscript>2</Subscript>S<Subscript>4</Subscript>

Phase equilibria in the FeSb₂S₄–FeLa₂S₄ system were studied by physicochemical analysis methods (differential thermal, X-ray powder diffraction, and microstructural analyses and microhardness and density measurements), and the phase diagram of the system was constructed. The formation of quaternary sulfide FeLaSbS₄ melting congruently at 1230 K, an analog of the mineral berthierite FeSb₂S₄, was detected. The X-ray powder diffraction analysis showed that FeLaSbS₄ belongs to the berthierite structural type and crystallizes in the orthorhombic system with the unit cell parameters a = 11.424 Å, b = 14.160 Å, c = 3.782 Å, Z = 4, and space group Pbam.     

Low-temperature heat capacity and high-temperature thermal behavior of sodium lutetium molybdate phosphate Na<Subscript>2</Subscript>Lu(MoO<Subscript>4</Subscript>)(PO<Subscript>4</Subscript>)

The low-temperature heat capacity of Na₂Lu (MoO₄)(PO₄) was measured by adiabatic calorimetry in the range of 7.47–345.74 K. The experimental data were used to calculate the thermodynamic functions of Na₂Lu (MoO₄)(PO₄). At 298.15 K, the following values were obtained: C _p ⁰ (298.15 K) = 237.7 ± 0.1 J/(K mol), S ⁰(298.15 K) = 278.1 ± 0.8 J/(K mol), H ⁰(298.15 K) ? H ⁰ (0 K) = 42330 ± 20 J/mol, and Φ⁰(298.15 K) = 136.1 ± 0. 3 J/(K mol). A heat capacity anomaly was found in the range of 10-67 K with a maximum at T _tr = 39.18 K. The entropy and enthalpy of transition are ΔS = 12.39 ± 0.75 J/(K mol) and ΔH = 403 ± 16 J/mol. The thermal investigation of sodium lutetium molybdate phosphate in the high-temperature range (623–1223 K) was performed using differential scanning calorimetry. It was found that during melting in the range of 1030–1200 K, Na₂Lu(MoO₄)(PO₄) degrades to simpler compounds; the degradation scenario is verified by X-ray powder diffraction.     

Sc<Subscript>2</Subscript>S<Subscript>3</Subscript>–Cu<Subscript>2</Subscript>S phase diagram

A phase diagram is constructed for the Sc₂S₃–Cu₂S system. The system forms two incongruently melting complex sulfides: hexagonal CuScS₂ (1Cu₂S: 1Sc₂S₃): a = 0.3734 nm, c = 0.6102 nm, space group P3m1, Т_m = 1635 K, ΔH_m = 1670 kJ/mol; and cubic CuSc₃S₅ (1Cu₂S: 3Sc₂S₃), a = 1.0481 nm, space group Fd3m, Т_m = 1835 K. In the 45–62 mol % Cu2S solid solution (ss) range, there is a singular point corresponding to the composition of compound CuScS₂ (50 mol % Cu₂S). The Sc₂S₃-based solubility at 1070 K is 14 mol % Cu₂S. In the γ-Cu₂S-based solid solution range, there is a peritectic point at 7 mol % Sc₂S₃, 1423 K.     

Electronic energy structure of As<Subscript>2</Subscript>S<Subscript>3</Subscript>, AsSI,AgAsS<Subscript>2</Subscript>, and TiS<Subscript>2</Subscript> semiconductors

Quantum-mechanical calculations with the FEFF8 code were used to study the electronic energy structure of 200-atomic clusters of As₂S₃, AsSI, AgAsS₂, and TiS₂ semiconductor compounds. The calculated local partial densities of electronic states are compared with the sulfur K and L X-ray emission spectra and sulfur K absorption spectra for fine powders of these compounds. Good agreement between theory and experiment has been obtained.     

Synthesis,structure, and physicochemical properties of the Cr(<Emphasis Type="Italic">iso</Emphasis>-Bu<Subscript>2</Subscript>PS<Subscript>2</Subscript>)<Subscript>3</Subscript> chelate compound

A paramagnetic (μ_ef = 3.86 BM) complex Cr(i-Bu₂PS₂)₃ (I) has been synthesized. Single crystals I were grown, and the crystal structure of the compound was determined from X-ray diffraction data (X8 APEX diffractometer, MoK _α radiation, 4516 F _hkl , R = 0.0604). Monoclinic crystals, space group P2₁/n, unit cell parameters a = 14.2665(5) Å, b = 11.4400(4) Å, c = 23.1299(8) Å, β = 90.245(1)°, V = 3775.0(2) ų, Z = 4, d _calc = 1.196 g/cm³. The structure is based on discrete mononuclear molecules. The coordination polyhedron of the Cr atom is a distorted S₆ octahedron formed from the S atoms of three cyclic bidentate ligands — i-Bu₂PS ₂ ⁻ ions. Electron spectroscopy data correspond to the octahedral structure of the CrS₆ chromophore. Original Russian Text Copyright ? 2007 by E. A. Sankova, L. A. Glinskaya, T. E. Kokina, R. F. Klevstova, and S. V. Larionov __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 48, No. 2, pp. 374–378, March–April, 2007.     

Subsolidus phase relations in the Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-Li<Subscript>2</Subscript>O-Ta<Subscript>2</Subscript>O<Subscript>5</Subscript> (Nb<Subscript>2</Subscript>O<Subscript>5</Subscript>) systems

The phase composition has been studied and an equilibrium phase diagram has been designed for the Al₂O₃-Li₂O-R₂O₅ (R = Ta or Nb) systems in the subsolidus region up to 1000°C and 85 mol % Li₂O. New phases with the composition Li_1+x Al_1?x O_2?x , where x = 0–0.67, have been found.     

Crystal structure and properties of [M(NH<Subscript>3</Subscript>)<Subscript>5</Subscript>Cl](NO<Subscript>3</Subscript>)<Subscript>2</Subscript>, (M = Ir,Rh, Ru)

The crystal structures of compounds from the series [M(NH₃)₅Cl](NO₃)₂, (M = Ir, Rh, Ru) were described. The compounds crystallized in the tetragonal crystal system, space group I4, Z = 2. Crystal data for [Ir(NH₃)₅Cl](NO₃)₂ (I): a = 7.6061(1) Å, b = 7.6061(1) Å, c = 10.4039(2) Å, V = 601.894(16) ų, ρ_calc = 2.410 g/cm³, R = 0.0087; [Rh(NH₃)₅Cl](NO₃)₂ (II): a = 7.5858(5) Å, b = 7.5858(5) Å, c = 10.41357(7) Å, V = 599.24(7) ų, ρ_calc = 1.926 g/cm³, R = 0.0255; [Ru(NH₃)₅Cl](NO₃)₂ (III): a = 7.5811(6) Å, b = 7.5811(6) Å, c = 10.5352(14) Å, V = 605.49(11) ų, ρ_calc = 1.896 g/cm³, R = 0.0266. The compounds were defined by IR spectroscopy and XRPA and thermal analyses.     

Structure and some properties of [UO<Subscript>2</Subscript>CrO<Subscript>4</Subscript>{CH<Subscript>3</Subscript>CON(CH<Subscript>3</Subscript>)<Subscript>2</Subscript>}<Subscript>2</Subscript>]

A new complex [UO₂CrO₄{CH₃CON(CH₃)₂}₂] (I) was studied by thermal analysis, IR spectroscopy, and X-ray crystallography. The crystals are monoclinic: a = 13.8108(11) Å, b = 8.6804(7) Å, c = 13.0989(10) Å, β = 104.777(1)°, V = 1518.4(2) ų, space group P2₁/c, Z = 4, R = 2.39%. The structure of I contains infinite chains of the [UO₂CrO₄{CH₃CON(CH₃)₂}₂] composition running along [001]; the complex belongs to the AT¹¹M¹ ₂ crystal-chemical group (A = UO ₂ ²⁺ , T¹¹ = CrO ₄ ^2? , M¹ = CH₃CON(CH₃)₂) of uranyl complexes. The chains are linked into a three-dimensional framework due to hydrogen bonds between oxygen atoms of chromate ions and hydrogen atoms of methyl groups of the dimethylacetamide.     

Crystal structure of KPb<Subscript>2</Subscript>Cl<Subscript>5</Subscript> and KPb<Subscript>2</Subscript>Br<Subscript>5</Subscript>

The KPb₂Cl₅ and KPb₂Br₅ crystals are monoclinic (P2₁/c) with a microtwinned structure. X-ray analysis of chloride resulted in the parameters a = 8.854(2) Å, b = 7.927(2) Å, c = 12.485(3) Å; β = 90.05(3)°, d_calc = 4.78(1) g/cm³ (STOE STADI4, MoK_α, 2θ_max = 80°), R₁ = 0.0702 for 4094 F ≥ 4 σ(F) reflections. For bromide, a = 9.256(2) Å, b = 8.365(2) Å, c = 13.025(3) Å; β = 90.00(3)°, d_calc = 5.62(1) g/cm³ (Bruker P4, MoK_α, 2θ_max = 70°), R₁ = 0.0692 for 3076 F ≥ 4 (F) reflections.     

Synthesis and X-ray investigation of Rb<Subscript>2</Subscript>[Pd(NO<Subscript>3</Subscript>)<Subscript>4</Subscript>] and Cs<Subscript>2</Subscript>[Pd(NO<Subscript>3</Subscript>)<Subscript>4</Subscript>]

Powder and single crystal X-ray diffraction studies have been performed for anhydrous nitrate complexes Rb₂[Pd(NO₃)₄] (I) and Cs₂[Pd(NO₃)₄] (II). Crystal data for I: a = 7.843(1) Å, b = 7.970(1) Å, c = 9.725(1) Å; β = 100.39(1)°, V = 597.9(1) Å ³, space group P2₁/c, Z = 2, d _calc = 2.918 g/cm³; for II: a = 10.309(2) Å, b = 10.426(2) Å, c = 11.839(2) Å; β = 108.17(3)°, V = 1209.0(4) ų, space group P2₁/c, Z = 4, d ^calc = 3.408 g/cm³. The structures are formed by isolated [Pd(NO₃)₄]^2? complex anions and alkali metal cations. The plane-square environment of the Pd atom is formed from the oxygen atoms of the monodentate nitrate groups. The geometrical characteristics of the complex anions are analyzed. Compound II has a short contact Pd...Cs 3.252 Å.     

Structural investigation of [Au(en)<Subscript>2</Subscript>]Cl(ReO<Subscript>4</Subscript>)<Subscript>2</Subscript> and [Au(en)<Subscript>2</Subscript>](ReO<Subscript>4</Subscript>)<Subscript>3</Subscript> complexes

Novel complex salts [Au(en)₂]Cl(ReO₄)₂ (I) and [Au(en)₂](ReO₄)₃ (II), en = ethylenediamine, are obtained. Their crystal structures are determined by single crystal X-ray diffraction. Complex I crystallizes in the triclinic crystal system: a = 6.2172(7) Å, b = 7.1644(8) Å, c = 8.8829(8) Å, α = 96.605(4)°, β = 110.000(4)°, γ = 97.802(4)°, P-1 space group, Z = 1, d _x = 3.905 g/cm³; complex II crystallizes in the monoclinic crystal system: a = 15.244(2) Å, b = 7.6809(8) Å, c = 9.3476(12) Å, β = 127.004(3)°, C2 space group, Z = 4, d _x = 4.057 g/cm³.     

Phase equilibria in the Tl-TlCl-Te system and thermodynamic properties of the compound Tl<Subscript>5</Subscript>Te<Subscript>2</Subscript>Cl

The Tl-Te-Cl system was studied in the Tl-TlCl-Te composition region by differential thermal analysis, X-ray powder diffraction, and emf and microhardness measurements. A series of polythermal sections, an isothermal section at 400 K, and a projection of the liquidus surface of the phase diagram were constructed. The ternary compound Tl₅Te₂Cl characterized by a wide homogeneity region and incongruent melting by a syntectic reaction at 708 K was shown to exist. This compound was found to crystallize in tetragonal lattice (space group I4/mcm) with the parameters a = 8.921 Å, c = 12.692 Å, Z = 4. Wide phase separation regions were also found in the system, including a three-phase separation region in the Tl-TlCl-Tl₂Te subsystem. Regions of primary crystallization of phases, and the types and coordinates of in- and monovariant equilibria in the T-x-y diagram were determined. From emf measurement data, the standard thermodynamic functions of formation and the standard entropy were calculated for the compound Tl₅Te₂Cl, as follows: ?ΔG ₂₉₈ ⁰ = 355.9 ± 1.1 kJ/mol, ?ΔH ₂₉₈ ⁰ = 377.1 ± 5.0 kJ/mol, and S ₂₉₈ ⁰ = 474.1 ± 6.8 J/(mol K).     

Low-temperature heat capacity of sodium erbium molybdophosphate Na<Subscript>2</Subscript>Er(MoO<Subscript>4</Subscript>)(PO<Subscript>4</Subscript>)

Adiabatic calorimetry is used to measure the low-temperature heat capacity of Na₂Er(MoO₄)(PO₄)from 6.41 to 347.87 K. Experimental data are used to calculate the thermodynamic functions of Na₂Er(MoO₄)(PO₄), which at 298.15 K are as follows: C _p ⁰ (298.15 K) = 243,3 ± 0.4 J/(K mol), S ⁰(298.15 K) = 312.8 ± 0.8 J/(K mol), H ⁰(298.15 K) ? H ⁰(0 K) = 45280 ± 90 J/mol, and Φ⁰(298.15 K) = 136.1 ± 0.3 J/(K mol). A diffuse heat-capacity anomaly associated with splitting of the Stark levels (Schottky anomaly) is discovered in the low-temperature region.     

Crystal Structure of New One-Dimensional Triple Molybdate Na<Subscript>2</Subscript>K<Subscript>2</Subscript>Cu(MoO<Subscript>4</Subscript>)<Subscript>3</Subscript>

The title compound (disodium dipotassium copper(II) tris-[molybdate (VI)]) is prepared by form melt and characterized by single crystal X-ray diffraction and UV-vis spectroscopy. It crystallizes in the triclinic space group P-1 with a = 7.4946(8) Å, b = 9.3428(9) Å, c = 9.3619(9) Å, α = 92.591(7)°, β = 105.247(9)°, γ = 105.496(9)°, V = 604.7 ų, and Z = 2. Its structure is isotypic with that of Na₄Mn(MoO₄)₃. It is formed by Cu₂O₁₀ distorted bi-octahedral dimers linked by two bridging bidentate Mo₂O₄ tetrahedra and, additionally, two monodentate Mo₁O₄ tetrahedra to form Cu₂Mo₄O₂₀ units. These units are linked by the insertion of Mo₃O₄ tetrahedra to build infinite ribbons disposed along the c axis. All of these ribbons form a one-dimensional framework. Both K1 and K3 cations are located in the inversion center, and all the other atoms are at general positions. The structure model is supported by the bond valence sum (BVS) and charge distribution CHARDI methods. The Cu²⁺ cations adopt the [4+2] CuO₆ Jahn-Teller distortion giving rise to an intense d–d transition in the UV-vis absorption spectra.