Crystal structure and magnetic properties of Ce7Ni5±xGe3±xIn6 and Pr7Ni5±xGe3±xIn6

The indides Ce₇Ni_5±xGe_3±xIn₆ and Pr₇Ni_5±xGe_3±xIn₆ were synthesized from the elements by arc-melting of the components. Single crystals were grown via special annealing sequences. Both structures were solved from X-ray single crystal diffraction data: new structure type, P6/m, Z=1, a=11.385(2), c=4.212(1) Å, wR₂=0.0640, 634F² values, 25 variables for Ce₇Ni_4.73Ge_3.27In₆ and a=11.355(6), c=4.183(2) Å, wR₂=0.0539, 563F² values, 25 variables for Pr₇Ni_4.96Ge_3.04In₆. Both indides show homogeneity ranges through Ni/Ge mixing (M sites). This new structure type can be derived from the AlB₂ structure type by a substitution of the Al and B atoms by CeM₁₂ and NiIn₆Ce₃ polyhedra (tricapped trigonal prism). Magnetic susceptibility measurements on a polycrystalline sample of Ce₇Ni₅Ge₃In₆ indicated Curie-Weiss like paramagnetic behavior down to 1.71 K with the effective magnetic moment slightly reduced in relation to the value expected for trivalent cerium ions. No magnetic ordering is evident.     

Synthesis and structural characterization of A3In2Ge4 and A5In3Ge6 (A=Ca, Sr, Eu, Yb)—New intermetallic compounds with complex structures, exhibiting Ge-Ge and In-In bonding

Reported are the synthesis and the structural characterization of four new polar intermetallic phases, which exist only with mixed alkaline-earth and rare-earth metal cations in narrow homogeneity ranges. (Sr_1-xCa_x)₅In₃Ge₆ and (Eu_1-xYb_x)₅In₃Ge₆ (x≈0.7) crystallize in the orthorhombic space group Pnma with two formula units per unit cell (own structure type, Pearson symbol oP56). The lattice parameters are as follows: a=13.109(3)-13.266(3) Å, b=4.4089(9)-4.4703(12) Å, and c=23.316(5)-23.557(6) Å. (Sr_1-xCa_x)₃In₂Ge₄ and (Sr_1-xYb_x)₃In₂Ge₄ (x≈0.4-0.5) adopt another novel monoclinic structure-type (space group C2/m, Z=4, Pearson symbol mS36) with lattice parameters in the range a=19.978(2)-20.202(2) Å, b=4.5287(5)-4.5664(5) Å, c=10.3295(12)-10.3447(10) Å, and β=98.214(2)-98.470(2)°, depending on the metal cations and their ratio. The polyanionic sub-structures in both cases are based on chains of InGe₄ corner-shared tetrahedra. The A₅In₃Ge₆ structure (A=Sr/Ca or Sr/Yb) also features Ge₄ tetramers, and isolated In atoms in nearly square-planar environment, while the A₃In₂Ge₄ structure (A=Sr/Ca or Eu/Yb) contains zig-zag chains of In and Ge strings with intricate topology of cis- and trans-bonds. The experimental results have been complemented by tight-binding linear muffin-tin orbital (LMTO) band structure calculations.     

New catalytic methods for the synthesis of vitamins K: K3, K4 and Vikasol

A series of catalysts is developed for synthesis of vitamins K from easily available l-naphthol. The corresponding catalytic reactions compose the background of VIKASIB technology, which is friendly to the enviroment.     

Local structure of Cu in Cs8Na16Cu5Ge131 type II clathrate

We have used X-ray absorption spectroscopy (XAS) to investigate the local structure of Cu and Ge in the Cs₈Na₁₆Cu₅Ge₁₃₁ type II clathrate. We show that the local structure parameters for Ge (coordination number and distances) are consistent with those derived on the basis of XRD investigation of Cs₈Na₁₆Ge₁₃₆. The EXAFS data suggest that Cu either randomly substitutes for Ge on the clathrate framework or preferentially on the 96g site but not preferentially on the 32e or 8a sites (Wyckoff notation). Furthermore, we find that the Cu-Ge distance is smaller than the Ge-Ge distance by 0.13 Å, indicating a local distortion around the Cu atoms. The estimated degrees of disorder for Cu-Ge and Ge-Ge interactions indicate the Cu-Ge clathrate framework to be relatively stiff, while those for Na-Ge and Cs-Ge interactions corroborate previous observations of strong thermal disorder of the alkali guests in these materials. Our XAS results offer insight into the site substitution of Cu in this material, information unattainable from X-ray diffraction due to the lack of scattering contrast between Cu and Ge.     

Preparation and properties of potassium pentafluorodioxo-tungstate (VI) K3WO2F5 and potassium octafluoropentaoxo-ditungstate (VI) K6W2O5F8

The potassium salts of two new hepta coordinated oxyfluoro anions of tungsten (VI) are reported in this paper. The monomer, K₃WO₂F₅ was obtained from the aqueous solution while the dimer, K₆W₂O₅F₈ was isolated from alcohol. The absorption peak of K₆W₂O₅F₈ at 830 cm^-1 has been attributed to W-O-W link. The W-O-W angle is found to be 155° and the force constant is 4.44 mdyn/A°. The d values obtained from x-ray powder diffraction studies are given.     

Structur–Composition Relations and Fractional Site Occupancy of New M5Ge4 Compounds in the System Ge–Ta–Zr

The new ternary phases Zr_4−xTa_1+xGe₄ (0.1<x<0.4) and Zr_2+xTa_3−xGe₄ (0.1<x<1.1) were prepared from the elements by arc melting and subsequent induction heating at 1400–1450°C. Single-crystal X-ray diffraction was used to determine their structures and to refine mixed site occupancies. Zr_4−xTa_1+xGe₄ was found to crystallize in the monoclinic space group P2₁/c (structure type: U₂Mo₃Si₄) and the compound Zr_2−xTa_3−xGe₄ shows orthorhombic symmetry (space group Pnma, structure type: Sm₅Ge₄). The close structural relationship between the two structures is discussed. Both phases exhibit pronounced differential fractional site occupancy of Ta and Zr on the metal sites and considerable composition ranges. Extended Hückel calculations were performed for various site occupancy models and Mulliken overlap populations for the different lattice sites of each structure were calculated for these models. The correlation of the cumulated Mulliken overlap populations and the atomic orbital populations with the actual site occupancies is discussed.     

Synthesis and Structure of a New Layered Zincophosphate Zn6(PO4)5(HPO4)·C8N5H28·5H2O, Intercalated with Quintuply Protonated Tetraethylenepentamine

A new two-dimensional zinc phosphate Zn₆(PO₄)₅(HPO₄)·C₈N₅H₂₈·5H₂O has been synthesized hydrothermally using tetraethylenepentamine (TEPA) as structure-directing agent and its structure was determined by means of single-crystal X-ray diffraction. The title compound crystallizes in the orthorhombic system, space group Pca2₁ (No.29) with lattice parameters a=18.6286(12) Å, b=8.0804(5) Å, c=22.5019(15) Å, V= 3387.1(4) ų, Z=4, R₁=0.0389 and wR₂=0.0862 [4042 observed reflections with I>2σ(I)]. The structure involves a network of ZnO₄, PO₄, and PO₃(OH) tetrahedra forming macroanionic inorganic layers with eight-membered apertures. The charge compensation is achieved by the quintuply protonated TEPA molecule in interlamellar space, which interact with the inorganic layers via hydrogen bonding.     

Phase relations in the system K2MoO4–KPO3–MoO3–Bi2O3: A new phosphate K3Bi5(PO4)6

Phase equilibrium in the pseudo-quaternary system K₂O–MoO₃–P₂O₅–Bi₂O₃ was studied as three-component solvent K₂MoO₄–KPO₃–MoO₃ containing 15 mol% Bi₂O₃ during slow cooling and spontaneous crystallization. The results of the investigation were shown on a composition diagram, which indicates the crystallization fields of K₂Bi(PO₄)(MoO₄), K₅Bi(MoO₄)₄, BiPO₄ and K₃Bi₅(PO₄)₆. New phosphate K₃Bi₅(PO₄)₆ was characterized by single-crystal X-ray diffraction (space group C2/c, a=17.680(4), b=6.9370(14), c=18.700(4) Å, β=113.79(3)°) and FTIR spectroscopy. The possibility of lone electron pair stereoactivity of bismuth was suggested using the calculations of characteristics of the Voronoi–Dirichlet polyhedra for K₃Bi₅(PO₄)₆ and K₂Bi(PO₄)(MoO₄).     

Ca3Ni8In4—An Ordered Noncentrosymmetric Variant of the BaLi4 Type

The title compound was synthesized by reacting the elements in an arc-melting apparatus under purified argon and subsequent annealing at 870 K. Ca₃Ni₈In₄ was investigated using X-ray diffraction on both powders and single crystals: P6₃mc, a=898.9(1) pm, c=752.2(2) pm, wR2=0.0591, 327 F² values, and 35 parameters. This structure is an ordered, noncentrosymmetric variant of the BaLi₄ type. The nickel and indium atoms build a complex three-dimensional [Ni₈In₄] polyanion in which the calcium atoms fill distorted hexagonal channels. To a first approximation the formula may be written as (3 Ca²⁺)⁶⁺ [Ni₈In₄]⁶⁻. Within the polyanion the Ni1, Ni3, and Ni4 atoms form one-dimensional cluster units which extend in the c direction while the Ni2 atoms have only indium neighbors in a distorted tetrahedral coordination. The Ni–Ni distances in the cluster range from 241 to 266 pm. The cluster units are surrounded and interconnected by indium atoms. The group– subgroup relation from centrosymmetric BaLi₄ to noncentrosymmetric Ca₃Ni₈In₄ is presented. Chemical bonding in Ca₃Ni₈In₄ and the structural relation with Lu₃Co_7.77Sn₄, Ca₃Au_6.61Ga_4.39, and Co₂Al₅ is briefly discussed.     

Ab initio study of the nature of the chemical bond and electronic structure of the layered phase Ca10(Pt4As8)(Fe2As2)5 as a parent system in the search for new superconducting iron-containing materials

Ab initio calculations were used in a detailed study of chemical bonding and electronic structure of the recently discovered superconducting tetragonal phase Ca₁₀(Pt₄As₈)(Fe₂As₂)₅ (T_C 25 K). The Ca₁₀(Pt₄As₈)(Fe₂As₂)₅ phase is metal-like, mainly due to the Fe3d states of the (Fe₂As₂)₅ blocks. The electronic spectrum of the (Pt₄As₈) blocks is similar to a semi-metal with very low density of states at the Fermi level. Chemical bonding in Ca₁₀(Pt₄As₈)(Fe₂As₂)₅ may be described as a mixture of anisotropic contributions of covalent, ionic, and metallic interatomic and inter-block interactions.     

Synthesis, characterization and thermochemistry of K2B5O8(OH)·2H2O

A pure hydrated potassium borate K₂B₅O₈(OH)·2H₂O has been synthesized under mild hydrothermal conditions and characterized by single-crystal X-ray diffraction, XRD, FT-IR, Raman spectra and DTA-TG. The crystal structure consists of two K-O polyhedra and [B₅O₈(OH)]²⁻ polyborate anion. The enthalpy of formation was determined to be −4772.6 ± 4.0 kJ mol⁻¹ by solution calorimetry.     

[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.     

Complex three-dimensional platinum-indium networks in the ternary indides Dy2Pt7In16 and Tb6Pt12In23

Well crystallized samples of Dy₂Pt₇In₁₆ and Tb₆Pt₁₂In₂₃ were synthesized by an indium flux technique. Arc-melted precursor alloys with the starting compositions ∼DyPt₃In₆ and ∼TbPtIn₄ were annealed with a slight excess of indium at 1200 K followed by slow cooling (5 K/h) to 870 K. Both indides were investigated by X-ray diffraction on powders and single crystals: Cmmm, a=1211.1(2), b=1997.8(3), c=439.50(6) pm, wR2=0.0518, 1138 F² values, 45 variable parameters for Dy₂Pt₇In₁₆ and C2/ma=2834.6(4), b=440.05(7), c=1477.1(3) pm, β=112.37(1)°, wR2=0.0753, 2543 F² values, 126 variable parameters for Tb₆Pt₁₂In₂₃. The platinum atoms in the terbium compound have a distorted trigonal prismatic coordination. In Dy₂Pt₇In₁₆, trigonal and square prismatic coordination occur. The shortest interatomic distances are observed for Pt-In followed by In-In contacts. Considering these strong interactions, both structures can be described by complex three-dimensional [Pt₇In₁₆] and [Pt₁₂In₂₃] networks. The networks leave distorted pentagonal channels in Dy₂Pt₇In₁₆, while pentagonal and hexagonal channels occur in Tb₆Pt₁₂In₂₃. The crystal chemistry and chemical bonding of the two indides are briefly discussed.     

Low-temperature luminescence of Eu3+ in K2EuCl5

The luminescence associated with the Eu³⁺ ion in K₂EuCl₅ has been studied at cryogenic temperatures under conditions of high resolution. Emission was observed to originate from both the ⁵D₀ and ⁵D₁ excited states, and transitions to the ${}^7\text{F}{}_0\text{,}{}^7\text{F}{}_1\text{,}{}^7\text{F}{}_2\text{,}{}^7\text{F}{}_3$, and ⁷F₄ ground levels were observed. The fine structure observed within these emission bands was found to be consistent with the existence of an effective C₄ site symmetry for the emitting Eu(III) species, even though the crystal structure does not indicate the presence of a true or pseudo C₄ axis.     

An inorganic complex of silver (III): K5Ag(IO5OH)2 · 8H2O

The chemical preparation and crystal structure of the trivalent silver salt K₅Ag(IO₅OH)₂ · 8H₂O are described (monoclinic, space group Cc; a = 21.79(4), b = 6.320(3), c = 15.16(3) Å, β = 96.14(4); four formula units per unit cell). The structure is refined until R = 0.033 for 2718 reflections. Isolated Ag(IO₅OH)^5?₂ units occur, which contain trivalent silver ions surrounded by four oxygen atoms from two IO₆ octahedra in rectangular configuration. The differences in the IO bond lengths, as well as the small deviations of the crystal structure from centrosymmetry, are in agreement with an antiperiplanar position of the OH groups in both octahedra.     

Synthesis and Structure of Ba8Cu3In4N5 with Nitridocuprate Groups and One-Dimensional Infinite Indium Clusters

Single crystals of the quaternary compound Ba₈Cu₃In₄N₅ were prepared by heating Ba, Cu, and In in a Na flux at 1023 K under 7 MPa of N₂, and by slow cooling from this temperature. The crystal structure was analyzed by single-crystal X-ray diffraction. It crystallizes in an orthorhombic cell (space group Immm (No. 71), Z=2) with a=4.0781(6), b=12.588(2), and c=19.804(3) Å at 298 K. The structural formula is expressed as Ba₈[CuN₂]₂ [CuN]In₄. Nitridocuprates of one-dimensional chains ¹_∞[CuN_2/2] and isolated units ⁰[CuN₂], and one-dimensional indium clusters ¹_∞[In₂In_4/2] are contained in the structure. A split-site model applied for the arrangement of ¹_∞[CuN_2/2] chains suggested that there is a short-bond, long-bond alternation of the Cu-N bondings. The electrical resistivity of Ba₈Cu₃In₄N₅ was 3.44 mΩ·cm at 298 K. A metallic temperature dependence of the resistivity was observed down to 10 K.     

Unusual Disordering of Potassium Ions in the Structures of Cluster Rhenium Thiohalides K3[Re6S7Br7] and K4[Re6S8Cl6]

New cluster compounds — rhenium and potassium thiohalides K₃Re₆S₇Br₇ (I) and K₄Re₆S₈Cl₆ (II) — have been synthesized. Their crystal structures have been determined by single crystal X-ray diffraction. The compounds are monoclinic; (I): space group P2₁/c, a = 9.32(1) Å, b = 13.528 Å, c = 12.413 Å, β = 110.21°, Z = 2, R = 0.038; (II): space group C2/m, a = 10.614 Å, b = 17.268 Å, c = 10.448 Å, β = 110.755°, Z = 2, R = 0.042. In both structures, the potassium ions are considerably distorted. The occupancies of the potassium sites are 0.17-0.34 (I) and 0. 01-0.26 (II), correlating well with the coordination numbers (c.n. 7-10 and 2-7 for I and II, respectively). In I, adjacent positions of potassium atoms are aggregated into discrete tetrahedral and angular clusters; in II, the individual (four-and six-membered) cyclic clusters of potassium sites are present along with bent chains of vertex-and edge-sharing tetrahedral “potassium clusters.” The shortest K-K distances in these “clusters” vary from 1.31 Å to 1.54 Å (I) and from 0.66 Å to 1.65 Å (II). The “instability” of the potassium site suggests that I and II are ion conductors.Original Russian Text Copyright © 2004 by S. F. Solodovnikov, S. S. Yarovoi, Yu. V. Mironov, A. V. Virovets, and V. E. Fedorov__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 5, pp. 909–917, September–October, 2004.     

Order in the disordered state: local structural entities in the fast ion conductor Ba2In2O5

The structural features of Ba₂In₂O₅ at high temperatures are discussed based on a thorough study of the full energy hypersurface of a 36 atoms supercell by periodic density functional theory. The results obtained for this cell are furthermore used for considering stacking-sequences and connectivity-patterns present only in larger supercells. The distribution of oxygen vacancies is far from random and relatively few configurations, associated with different arrangements of tetrahedral InO₄, square pyramidal InO₅ and octahedral InO₆ entities, are thermally accessible at most temperatures. Our results call into the question of commonly used defect models for such grossly disordered materials in which oxygen vacancies are distributed at random over a number of lattice sites. The energetic preference for certain structural entities also has important implications for ionic transport due to restraints imposed by local symmetry.     

Phase formation in the K2MoO4-Lu2(MoO4)-Hf(MoO4)2 system and the structural study of triple molybdate K5LuHf(MoO4)6

Interactions in the ternary system K₂MoO₄-Lu₂(MoO₄)₃-Hf(MoO₄)₂ have been studied by X-ray powder diffraction and differential thermal analysis. A new triple (potassium lutetium hafnium) molybdate with the 5: 1: 2 stoichiometry has been found. Single crystals of this molybdate have been grown. Its X-ray diffraction structure has been refined (an X8 APEX automated diffractometer, MoK _α radiation, 1960 F(hkl), R = 0.0166). The trigonal unit cell has the following parameters: a = 10.6536(1) ?, c = 37.8434(8) ?, V = 3719.75(9) ?, Z = 6, space group R c. The mixed 3D framework of the structure is built of Mo tetrahedra sharing corners with two independent (Lu,Hf)O₆ octahedra. Two sorts of potassium atoms occupy large framework voids. Original Russian Text ? E.Yu. Romanova, B.G. Bazarov, R.F. Klevtsova, L.A. Glinskaya, Yu.L. Tushinova, K.N. Fedorov, Zh.G. Bazarova, 2007, published in Zhurnal Neorganicheskoi Khimii, 2007, Vol. 52, No. 5, pp. 815–818.     

New compounds A 3+ Te6+M 33+ X 25+ O14 (A = Na, K; M = Ga, Al, Fe; X = P, As, V) with the Ca3Ga2Ge4O14 structure

Compounds A₃⁺Te⁶⁺M₃³⁺X₂⁵⁺O₁₄ (A = Na, K; M = Ga, Al, Fe; X = P, As, V) with the Ca₃Ga₂Ge₄O₁₄ structure (sp. gr. P321) were prepared by solid-phase synthesis at 600–850°C in air. The compounds melt incongruently or decompose in the solid state.