Preparation and crystal structure of a new barium silicon nitride, Ba5Si2N6

Single crystals of a new ternary nitride, Ba₅Si₂N₆, were synthesized by slow cooling from 750°C using a starting mixture of Ba, Si, Na and NaN₃, where Na and NaN₃ were a flux and a nitrogen source respectively. It crystallizes with orthorhombic symmetry: space group P2₁2₁2₁ (No. 19), A = 6.159, B = 10.305, C = 15.292 Å, and Z = 4. The crystal structure was determined from single-crystal data and refined to R1 = 0.0495 for all 1637 observed reflections and 89 variables. A pair of SiN₄ tetrahedra contained in the structure forms a nitridometallate anion of [Si₂N₆]¹⁰ by edge sharing.     

LaMg2NiH7, a novel quaternary metal hydride containing tetrahedral [NiH4] complexes and hydride anions

A new ternary compound of composition LaMg₂Ni has been found and investigated with respect to structure and hydrogenation properties. It crystallizes with the orthorhombic MgAl₂Cu type structure (space group Cmcm, a=4.2266(6), b=10.303(1), c=8.360(1) Å; V=364.0(1) ų; Z=4) and absorbs hydrogen near ambient conditions (<200 °C, <8 bar) thereby forming the quaternary metal hydride LaMg₂NiH₇. Neutron powder diffraction on the deuteride revealed a monoclinic distorted metal atom substructure (LaMg₂NiD₇: space group P2₁/c, a=13.9789(7), b=4.7026(2), c=16.0251(8) Å; β=125.240(3)°, V=860.39(8) ų; Z=8) that contains two symmetry independent tetrahedral [NiD₄]⁴⁻ complexes with Ni–D bond lengths in the range 1.49–1.64 Å, and six D⁻anions in tetrahedral metal configuration with bond distances in the ranges 1.82–2.65 Å (Mg) and 2.33–2.59 Å (La). The compound constitutes a link between metallic ‘interstitial’ hydrides and non-metallic ‘complex’ metal hydrides.     

LiMg2RuH7, a new quaternary metal hydride containing octahedral [Ru(H)H6] complex anions

LiMg₂RuH₇ and its deuteride were synthesized by sintering mixtures of LiH, magnesium and ruthenium powders at 500–550 °C and a hydrogen (deuterium) pressure of 120–155 bar, and characterized by X-ray and neutron powder diffraction. The yellow powder crystallizes with hexagonal symmetry (space group, P6₃/mmc; hydride - A = 4.7060(1) Å, C = 10.6960(2) Å; deuteride - A = 4.6998(1) Å, C = 10.6674(3) Å). The structure is an ordered substitution variant of Mg₃ReH₇. It contains a nearly regular octahedral 18-electron [Ru(II)D₆]⁴⁻ complex with bond distances [Ru-6D1] = 1.704(7) Å, and a deuteride anion D⁻ coordinated in a trigonal bipyramidal configuration by two close magnesium and three distant lithium cations with bond distances [D2-2Mg] = 1.852(6) Å and [D2−3Li] = 2.7134(1) Å respectively.     

Synthesis and crystal structure of iron(III) selenate(IV) trihydrate, Fe2(SeO3)3 • 3H2O

The crystal structure of iron(III) selenate(IV) trihydrate, Fe₂(SeO₃)₃ • 3H₂O, space group R3c, a = 9.360(1) Å, C = 20.297(2) Å, V = 1539.98 ų, Z = 6, was determined by single-crytal X-ray diffraction methods, 926 unique data, measured up to 2θ = 70° (Mo K radiation); R, R(I)w = 0.034, 0.088. Fe₂(SeO₃)₃ • 3H₂O is isotypic with the analogues Al, Ga and Cr compounds and was synthesized under moderate hydrothermal conditions.     

The crystal structure of the novel ternary silicide Sm4Pd4Si3

The crystal structure of the compound Sm₄Pd₄Si₃ was determined by the single-crystal method (KM-4 automatic diffractometer, Mo K radiation. Sm₄Pd₄Si₄ has the monoclinic Nd₄Rh₄Ge, type structure: space C2/c, mC44 (No. 15). a = 20.693(6), B = 5.584(1), C = 7.699(2) Å, β = 109.48(3)°, V = 838 Å, Z = 4, μ - 36.23 mm¹, R =_F = 0.0537, R _F = 0.0435 for 1652 unique reflections. The coordination numbers of samarium atoms are 17 and 18. For palladium and silicon atoms icosahedra and trigonal prisms with additional atoms are typical as coordination polyhedra. The structure of Sm₄Pd₄Si₄ is composed of fragments of the YPd₂Si and Y₁Rh₂Si₂ structure in a ratio 1:1.     

Structural investigation of ternary RIr3B2 compounds (R=Ce and Pr)

Structural studies were performed for the ternary RIr₃B₂ compounds (R=Ce and Pr) from as cast samples. The crystal structure of the ternary boride CeIr₃B₂ (CeCo₃B₂ structure type, space group P6/mmm, a=5.520(3) Å, c=3.066(2) Å, Z=1, V=80.91 ų, ρ_x=15.154 g cm⁻³) was refined to R₁=0.0470, wR₂=0.1240 from single-crystal X-ray diffraction data. The new ternary boride PrIr₃B₂ was found to be isostructural with the CeIr₃B₂ compound. Its lattice parameters a=5.5105(2) Å, c=3.1031(1) Å were obtained from a Rietveld refinement of X-ray powder diffraction data.     

Hydrothermal synthesis and characterization of a new layered compound Li2VGeO5

The new compound Li₂VGeO₅ with a layered structure has been synthesized at 580 °C via the hydrothermal method. The compound crystallizes in the space group P4/n of the tetragonal system with two formula units in a cell of dimensions a=6.5187(9) Å, c=4.5092(9) Å (T=298 K), V=191.61(5) Å³. The structure is composed of layers made of repeating [(VO₅)(GeO₄)]¹⁻ units. Li⁺ ions reside between the layers. The magnetic susceptibility data show an antiferromagnetic coupling below 5 K with C=0.47 emu K mol⁻¹, and θ=−13 K with μ_eff=1.89μ_B for each Li₂VGeO₅ unit.     

Synthesis and crystal structure of CaAgBi and BaAg1.837Bi2

Two ternary alkali earth silver bismuthides, CaAgBi and BaAg_1.837Bi₂, have been synthesized by solid-state reactions of the corresponding metals in welded Nb tubes at high temperature. Their structures have been established by single-crystal X-ray diffraction studies. CaAgBi crystallizes in the hexagonal space group P6₃mc (No.186) with cell parameters of a = b = 4.8113(4) Å, c = 7.8273(9) Å, V = 156.92(3) Å³, and Z = 2. BaAg_1.837Bi₂ belongs to tetragonal space group P4/nmm (No.129) with cell parameters of a = b = 4.9202(2) Å, c = 11.628(1) Å, V = 281.50(3) Å³, and Z = 2. The structure of CaAgBi is of the LiGaGe type, and features a three-dimensional four-connected (3D4C) anionic network with Ca²⁺ encapsulated in the channels formed by [Ag₃Bi₃] six-membered rings. BaAg_1.837Bi₂ is isostructural with CaBe₂Ge₂, a variant of the tetragonal ThCr₂Si₂-type structure. Its structure exhibits a three-dimensional anionic network built of (0 0 1) and (0 0 2) puckered [Ag₂Bi₂] layers interconnected via additional Ag–Bi bonds along the c-axis. BaAg_1.837Bi₂ is metallic based on band structure calculations.     

The structure of Li3Cu2O4, a compound with formal mixed valence

The structure of Li₃Cu₂O₄ was solved from X-ray powder diffraction data and refined from a multiphase specimen using the Rietveld method. The cuprate crystallizes in C2/m with Z = 2. The compound has a small homogeneity range. Typical parameters are a = 9.946(5) Å, B= 2.778(2) Å, C = 7.260(5) Å and β = 119.10(2)°. The structure may be described as an ordered intergrowth of slabs of Li₂CuO₂ and hypothetical LiCuO₂ of NaCuO₂ type. The formula suggests a copper(II, III) mixture, but there is only one crystallographic copper site which implies a more appropriate formulation as Li₃⁺[Cu(II)O₂]₂^3/2 with parallel strands of edge-coupled CuO₄ units running along the b axis.     

Zur Kenntnis von RbBa3Ca4Cu3V7O28

Single crystals of RbBa₃Ca₄Cu₃V₇O₂₈ were prepared above the melting point of the reaction mixture. It crystallizes with hexagonal symmetry, space group C_6V⁴-P6₃mc, a 11.1751, c 12.434 Å, Z = 2. RbBa₃Ca₄Cu₃V₇O₂₈ is the second member of a new structure type of the copper-oxovanadates. Ba²⁺ shows an unusual 12-fold coordination. The two calcium positions are coordinated by trigonal prisms and octahedra respectively. The copper coordination is characterized by a stretched square pyramid. The Cu²⁺ ions are outside the centre nearly in plane of the pyramids.

Zusammenfassung

Einkristalle von RbBa₃Ca₄Cu₃V₇O₂₈ wurden oberhalb des Schmelzpunktes der Reaktionsmischung erhalten. Die Verbindung kristallisiert hexagonal, Raumgruppe C_6V⁴-P6₃mc, a 11.1751, c 12.434 Å, Z = 2. RbBa₃Ca₄Cu₃V₇O₂₈ ist das zweite Beispiel für einen neuen Strukturtyp der Kupfer-Oxovanadate, mit 12-fach koordinierten Ba²⁺ -Ionen. Die zwei Calciumpositionen sind trigonal prismatisch bzw. oktaedrisch koordiniert. Die Koordination der Cu²⁺-Ionen ist durch eine gestreckte Pyramide charakterisiert. Cu²⁺ ist auβerhalb des Polyederzentrums nahezu in der quadratischen Fläche der Pyramide angeordnet.     

High-pressure synthesis and crystal structures of two new polyphosphides, NaP5 and CeP5

Two novel polyphosphides, NaP₅ and CeP₅, were prepared in a BN crucible by the reaction of elemental components under a high pressure of 3 GPa at 800–950 °C. The X-ray structural analysis showed that NaP₅ crystallizes in an orthorhombic space group Pnma with a=10.993(2) Å, b=6.524(1) Å, c=6.903(1) Å, Z=4 and CeP₅ in the monoclinic group P2₁/m with a=4.9143(5) Å, b=9.6226(8) Å, c=5.5152(4) Å, β=104.303(6)°, Z=2. The crystal structure of NaP₅ consists of a three-dimensional framework _∞³[P₅]¹⁻ constructed by P---P bonds among four crystallographically inequivalent phosphorus sites, with large channels hosting the sodium cations, while CeP₅ is a layered compound containing _∞²[P₅]³⁻ polyanionic layers that are separated by Ce³⁺ ions. NaP₅ exhibits the diamagnetic behavior, while the temperature-dependent magnetic susceptibility of CeP₅ essentially follows the Curie–Weiss law.     

Ce(Au,Sb)2 with UHg2 structure type, a new member of the AlB2 family

A new ternary compound Ce(Au,Sb)₂, with a homogeneity range has been observed from X-ray powder diffraction of as cast alloys, a = 4.743–4.712 Å, c = 3.567–3.768 Å. Its crystal structure was investigated by X-ray diffraction from Ce(Au_1−xSb_x)₂ (x = 0.266) single crystal: CAD-4 automatic diffractometer, Mo K radiation, a = 4.7256(6) Å, c = 3.6711(6) Å, P6/mmm space group, V = 70.997(17) Å³, Z = 1, ρ = 10.732 Mg/m³, μ = 76.369 mm⁻¹, R₁ = 0.0415, wR₂ = 0.0793 for 99 reflections with I > 2σ(I₀). The coordination polyhedron of X (X = 0.734Au + 0.266Sb) atom is a full-capped trigonal prism [XCe₆X₃X₂]. Ce atom is coordinated by 14 atoms: [CeX₁₂Ce₂]. The compound is isotypic with UHg₂ structure, a deformation derivative of AlB₂ structure type. It forms isostructural compounds with La and Pr.     

Structural chemistry and magnetism of dicyclopentadienidehalides of lanthanides Part 8: terbiumdicyclopentadienidebromide [Tb(C5H5)2Br]2

A single-crystal X-ray structural investigation of [Tb(C₅H₅)₂Br]₂ revealed the [Sc(C₅H₅)₂Cl]₂-type structure, space group P2₁/c, with a = 1407.6(2) pm, b = 1644.7(2) pm, c = 1370.6(9) pm, β = 93.46(3)°, V = 3167(2) × 10⁶ pm³, D_c = 2.322 g cm⁻³ and Z = 6 dimers (R = 0.036 for 4627 reflections with I > 3σ(I)). The metal centres have the pseudosymmetry C_2v. Magnetic susceptibility data show Curie-Weiss behaviour between 213 and 6 K with θ_p = −4.5(3) K and a magnetic moment μ = 9.8(1) μ_B close to the Tb³⁺ free-ion value (9.72 μ_B). Below 6 K, deviations from Curie-Weiss behaviour are observed, and at 5.3 K a maximum in the susceptibility is detected which may be caused by intradimer antiferromagnetic spin coupling. The magnetic properties are compared with the prediction of various models, starting from cubic crystal fields and isotropic intramolecular exchange interactions, followed by extension to lower crystal field symmetry (orthorhombic) and anisotropic contributions to the spin coupling. However, a reasonable agreement between the measured and calculated data was not obtained. As in [Gd(C₅H₅)₂Br]₂, the low-temperature behaviour is governed by effects which cannot be described by spin coupling models in the generally accepted form.     

Crystal structure and magnetism of the Y2Pd14B5 compound

The crystal structure of the ternary boride Y₂Pd₁₄B₅, space group I4₁/amd, a=8.484(2) Å, c=16.490(3) Å, V=1186.98 ų, Z=4, was refined down to R=0.0475, wR2=0.1276 from single crystal X-ray diffraction data. Two types of coordination for boron atoms were observed: the coordination sphere for the B1 atom is a trigonal prism with one additional atom; the B2 atom has only four neighboring atoms which form a square. No boron–boron contact was observed. Analysis of the Y₂Pd₁₄B₅ crystal structure shows the existence of a correlation between this structure and the Sc₄Ni₂₉B₁₀ structure type. Magnetization and AC susceptibility measurements indicate that there is no superconducting or magnetic transition in Y₂Pd₁₄B₅ down to 2 K.     

Synthesis and structure of TlCuTiTe3

The new compound TlCuTiTe₃ has been synthesized from Tl₆Te₄ and the corresponding elements and characterized by single-crystal X-ray diffraction methods. TlCuTiTe₃ crystallizes in the space group C_2b²−P2₁/m of the monoclinic system with two formula units in a cell of dimensions a = 8.409(8) Å, B = 3.956(3) Å, C = 10.261(8) Å, β = 111.56(4)°, V = 317.5(4) ų (T = 115 K). The two-dimensional structure comprises slabs of alternating pairs of Ti octahedra and Cu tetrahedra. The slabs are separated by Tl′ cations coordinated to Te³ anions in a monocapped trigonal prismatic fashion. Whereas the structure of the individual slabs in TlCuTiTe₄, is strikingly similar to those found in the related materials NaCuTiS₃, NaCuZrSe₃, and NaCuZrTe₃, the packing of the slabs is different. Two-probe resistivity measurements indicate that TlCuTiTe₃ is a semiconductor.     

Synthesis and structure of a potassium nitridoditungstenate (K6W2N4O3), a potassium digermanate (K6Ge2O7) and a rubidium digermanate (Rb6Ge2O7)

Light yellow single crystals of potassium nitridoditungstate (K₆W₂N₄O₃) and pale single crystals of potassium digermanate (K₆Ge₂O₇) were obtained by the reaction of the metal oxides WO₃ (molar ratio, 1 : 15.7) or GeO₂ (molar ratio, 1 : 2) in alkali metal amide melts in an autoclave at 530–600 °C for 6–8 days. Colourless single crystals of rubidium digermanate (Rb₆Ge₂O₇) were prepared by the reaction of GeO₂ with rubidium amide (molar ratio, 1 : 2) in ammonia at 350 °C in a high-pressure autoclave (H. Jacobs and D. Schmidt, in E. Kaldis (ed.), High-pressure Ammonolysis in Solid State Chemistry, Current Topics in Materials Science, Vol. 8, North Holland, Amsterdam, 1981, p. 379) (p(NH₃) = 5.5 kbar) for 10 days. In all three cases other nitrogen-containing products were present.

The structures of the title compounds were determined on the basis of single-crystal data. They are isotypic or structurally closely related to each other: K₆W₂N₄O₃: P2₁/n, a = 6.720(2) Å, b = 9.473(1) Å, c = 9.581(2) Å, β = 91.99(2)°, Z = 2, R/R_w = 0.040/0.048, N(I) > 3σ(I) 2057, N(Var.) = 71. K₆Ge₂O₇: Pn, a = 6.529(2) Å, b = 9.079(4) Å, c = 9.162(6)Å, β = 91.85(4)°, Z = 2, R/R_w = 0.022/0.024, N(I) 3σ(I) = 1486, N(Var.) = 135. Rb₆Ge₂O₇: P2₁/n, a = 6.839(4) Å, b = 9.437(6) Å, c = 9.460(6) Å, β = 91.53(5)°, Z = 2, R/R_w = 0.061/0.074, N(I) 3σ(I) = 1055, N(Var.) = 71.     

Two polymorphs of Ba3Sn2P4: Single crystal and electronic structures

Two polymorphs (I and II) of Ba₃Sn₂P₄ have been found in the same preparative batch. Both compounds crystallize in the centrosymmetric monoclinic space group P2₁/c (#14, a = 7.8669(2) Å, b = 19.2378(5) Å, c = 7.8472(2) Å, β = 112.77(1)°, V = 1095.06(5) Å³, Z = 4, and R/wR = 0.0303/0.0710 for I; a = 7.8771(3) Å, b = 19.4099(7) Å, c = 7.7040(3) Å, β = 112.44(1)°, V = 1088.67(7) Å³, Z = 4, and R/wR = 0.0224/0.0415 for II). Both structures consist of one-dimensional chains separated by Ba²⁺ cations. The isolated chain consists of condensed ethane-like [Sn₂P₆] units. In polymorphs I and II, the condensation and connectivity of the [Sn₂P₆] units are quite different. While [Sn₂P₆] units form four- and six-membered rings in I, they form the five-membered rings in II. The electronic structure calculations indicate that semiconducting behavior is expected for both compounds.     

Synthese und kristallstruktur von KCr0,8Al0,2Mo2O8

Single crystals of KCr_0.8Al_0.2Mo₂O₈ were prepared and investigated by the X-ray diffractometer technique. It shows a structure type related to trigonal KAIMo₂O₈, monoclinic NaCrMo₂O₈ or orthorhombic KInMo₂O₈, space group C_2h⁶—C2/c; a=17.445 Å, b=5.649 Å, c=8.997 Å, β=119.37°; Z=4. KCr_0.8Al_0.2Mo₂O₈ is characterized by isolated MoO₄ tetrahedra, isolated (Cr/Al)O₆ octahedra and a distorted square antiprism around K⁺. The crystal structure is discussed with respect to those of related compounds.

Zusammenfassung

Einkristalle von KCr_0.8Al_0.2Mo₂O₈ wurden synthetisiert und mit Vierkreisdiffraktometertechnik röntgenographisch untersucht. Sie zeigen einen mit trigonal-KA1Mo₂O₈, monoklin-NaCrMo₂O₈ oder orthorhombisch-KlnMo₂O₈ verwandten Strukturtyp, Raumgruppe C_2h⁶—C2/c; a=17,445 Å, b=5,649 Å, c=8,997 Å, β=119,37°; Z=4. KCr_0.8Al_0.2Mo₂O₈ zeichnet sich durch isolierte MoO₄-Tetraeder, isolierte (Cr/Al)O₆-Oktaeder und ein verzerrtes quadratisches Antiprisma um K⁺ aus. Die Kristallstruktur wird mit solchen verwandter Verbindungen diskutiert.     

The ternary system Au---Co---Sn and the crystal structure of AuCo2(1−a)Sn4

The phase relations in the ternary system Au---Co---S have been studied by powder X-ray diffraction, metallography, electron microprobe analysis, and thermal analysis. The condensed phases occurring, tie-lines and tie-triangles are presented for an isothermal section of the phase diagram at 380°C. A hitherto unknown genuine ternary phase AuCo_2(1−a)Sn₄ is found, with 0.167 u 0.180, and as indicated by the formula, the non-stoichiometry is of the subtractional kind (confirmed by density measurements). The unit cell is monoclinic (space group C2/m) with a = 1260.3(3), B = 421.3(1), C = 522.9(1) pm and β = 104.62(2)° for u = 0.167. Au in 2a: (0.833) Co, Sn(I) and Sn(II) in 4i with x = 0.2116(2), Z = 0.3331(5) for Co, x = 0.41759(9), Z = 0.6493(2) for Sn(I) and x = 0.18489(9), Z = 0.8142(2) for Sn(II). The structure of AuCo_2(1−a)Sn₄ is of the Ni_3−xSn₄ type and its atomic arrangement is discussed in relation to that of the prototype. AuCo_2(1−a)Sn₄ behaves as a virtually ideal Curie paramagnet with μ_p = 1.191(3) μ_u per Co atom.     

X-ray investigations of ternary R3Pd4Ge4 samples

Ternary R₃Pd₄Ge₄ samples (R=Nd, Eu, Er) were investigated by means of X-ray single crystal (four circle diffractometer Philips PW1100, MoK radiation) and powder diffraction (MX Labo diffractometer, CuK radiation). The Er₃Pd_3.68(1)Ge₄ compound belongs to the Gd₃Cu₄Ge₄ structure type, space group Immm, a=4.220(2) Å, b=6.843(2) Å, c=14.078(3) Å, R₁=0.0484 for 598 reflections with F_o>4σ(F_o) from X-ray single crystal diffraction data. No ternary R₃Pd₄Ge₄ compound when R is Nd or Eu was observed. The Nd and Eu containing samples appeared to be multiphase. Ternary phases observed in the Nd₃Pd₄Ge₄ and Eu₃Pd₄Ge₄ alloys and their crystallographic characteristics are the following: NdPd₂Ge₂, CeGa₂Al₂ structure type, space group I4/mmm, a=4.3010(2) Å, c=10.0633(2) Å (X-ray powder diffraction data); NdPd_0.6Ge_1.4, AlB₂ structure type, space group P6/mmm, a=4.2305(2) Å, c=4.1723(2) Å (X-ray powder diffraction data); Nd(Pd_0.464(1)Ge_0.536(1))₂, KHg₂ structure type, space group Imma, a=4.469(2) Å, b=7.214(2) Å, c=7.651(3) Å, R₁=0.0402 for 189 reflections with F_o>4σ(F_o) (X-ray single crystal diffraction data); Eu(Pd,Ge)₂, AlB₂ structure type, space group P6/mmm, a=4.311(2) Å, c=4.235(2) Å; EuPdGe, EuNiGe structure type, space group P2₁/c, and ternary compound with unknown structure (X-ray powder diffraction data).