Three Crystal Structures,One Chemical Formula – Barium Dihydrogen‐hypodiphosphate(IV)‐dihydrate,BaH2P2O6·2H2O

Three polymorphs of barium dihydrogen‐hypodiphosphate(IV)‐dihydrate, BaH₂P₂O₆ · 2H₂O ( A , B and C ), were obtained and structurally characterized by single‐crystal X‐ray diffraction. A crystallizes in the monoclinic space group P2₁/n (no. 14) with a = 7.459(1) Å, b = 8.066(1) Å, c = 12.460(2) Å, β = 91.27(1) ° and Z = 4. B crystallizes in the monoclinic space group C2/c (no. 15) with a = 11.049(8) Å, b = 6.486(3) Å, c = 10.956(6) Å, β = 106.89(5) ° and Z = 4. C crystallizes in the orthorhombic space group C222₁ (no. 20) with a = 9.193(3) Å, b = 6.199(2) Å, c = 12.888(4) Å and Z = 4. Discrete [H₂P₂O₆]^2– units, barium cations and water molecules, held together by intermolecular hydrogen bonds of the type O–H ··· O, build up the structures of the three polymorphs. The phase purity of A and C was verified by powder diffraction measurements.     

The Periodate‐Based Double Perovskites M2NaIO6 (M = Ca,Sr, and Ba)

The crystal structures of the M₂NaIO₆ series (M = Ca, Sr, Ba), prepared at 650 °C by ceramic methods, were determined from conventional laboratory X‐ray powder diffraction data. Synthesis and crystal growth were made by oxidizing I^– with O₂^(air) to I⁷⁺ followed by crystal growth in the presence of NaF as mineralizator, or by the reaction of the alkali‐metal periodate with the alkaline‐earth metal hydroxide. All three compounds are insoluble and stable in water. The barium compound crystallizes in the cubic space group Fm3m (no. 225) with lattice parameters of a = 8.3384(1) Å, whereas the strontium and calcium compounds crystallize in the monoclinic space group P2₁/c (no. 14) with a = 5.7600(1) Å, b = 5.7759(1) Å, c = 9.9742(1) Å, β = 125.362(1)° and a = 5.5376(1) Å, b = 5.7911(1) Å, c = 9.6055(1) Å, β = 124.300(1)°, respectively. The crystal structure consists of either symmetric (for Ba) or distorted (for Sr and Ca) perovskite superstructures. Ba₂NaIO₆ contains the first perfectly octahedral [IO₆]^5– unit reported. The compounds of the ortho‐periodates are stable up to 800 °C. Spectroscopic measurements as well as DFT calculations show a reasonable agreement between calculated and observed IR‐ and Raman‐active vibrations.     

The Crystal Structure of Ba58Ga22F180O

The crystal structure of Ba₅₈Ga₂₂F₁₈₀O is established by means of X‐ray single crystal diffraction. It is tetragonal: a = 22.033(1) Å, c = 17.626(1) Å, Z = 2. The structure is solved in the space group I4/mmm (n° 139), using 3219 independent reflections. It is mainly built from a deficient arrangement of fluorite‐type [FBa₄] tetrahedra connected by edges and vertices which constitutes the skeleton of the structure, giving rise to large cavities in which lie isolated fluorine ions in tetrahedral and octahedral barium environment, isolated [F₂Ba₆] bitetrahedra, isolated barium ions in eight‐coordination of fluorine and a complex arrangement of isolated [GaF₆] octahedra and isolated [Ga₂F₁₀O] bioctahedra.     

The phase relations in the In2O3A2O3BO systems at elevated temperatures [A: Fe or Ga, B: Cu or Co]

The phase relations in the In₂O₃Fe₂O₃CuO system at 1000°C, the In₂O₃Ga₂O₃CuO system at 1000°C, the In₂O₃Fe₂O₃CoO system at 1300°C, and the In₂O₃Ga₂O₃CoO system at 1300°C were determined by means of a classical quenching method. InFeCuO₄ (a = 3.3743(4) Å, c = 24.841(5) Å), InGaCuO₄ (a = 3.3497(2) Å, c = 24.822(3) Å), and InGaCoO₄ (a = 3.3091(2) Å, c = 25.859(4) Å) having the YbFe₂O₄ crystal structure, In₂Fe₂CuO₇ (a = 3.3515(2) Å, c = 28.871(3) Å), In₂Ga₂CuO₇ (a = 3.3319(1) Å, c = 28.697(2) Å), and In₂FeGaCuO₇ (a = 3.3421(2) Å, c = 28.817(3) Å) having the Yb₂Fe₃O₇ crystal structure, and In₃Fe₃CuO₁₀ (a = 3.3432(3) Å, c = 61.806(6) Å) having the Yb₃Fe₄O₁₀ crystal structure were found as the stable ternary phases. There is a continuous series of solid solutions between InFeCoO₄ and Fe₂CoO₄ which have the spinel structure at 1300°C. The crystal chemical roles of Fe³⁺ and Ga³⁺ in the present ternary systems were qualitatively compared.     

Crystal-structure refinement, thermal expansion, and chemical distortion of Bi2Ga4O9

Single crystals of Bi₂Ga₄O₉ are grown from a solution in a bismuth oxide melt. The structure (orthorhombic, space group Pbam, a = 7.918(2) Å, b = 8.299(2) Å, c = 5.894(2) Å, Z = 2) is refined to R = 0.052 in the anisotropic approximation based on single-crystal X-ray diffraction data. The structure is a framework. The bismuth(III) atoms are sixfold coordinated; gallium(III) exists in both tetrahedral and octahedral coordinations. The thermal expansion of Bi₂Ga₄O₉ is studied by high-temperature X-ray powder diffraction method and is found to be sharply anisotropic. A structural interpretation of the anisotropy is proposed. Chemical distortion in the Bi₂M₄O₉ compounds with M = Fe(III), Al, or Ga is analyzed and compared with the thermal expansion of Bi₂Ga₄O₉.     

Structural and Raman Spectroscopic Investigations of K4BaSi3O9 and K4CaSi3O9

The crystal structures of K₄BaSi₃O₉ and K₄CaSi₃O₉ have been characterized by X‐ray diffraction techniques as well as Raman spectroscopy. The structure of K₄CaSi₃O₉ has been refined from powder diffraction data via the Rietveld method using polycrystalline material prepared from solid state reactions. The compound is isostructural with form I of K₄SrSi₃O₉. It crystallizes with 16 formula units in a cubic primitive cell (a = 15.94014(3) Å, V = 4050.20(1) ų) and adopts space group . K₄CaSi₃O₉ belongs to the group of cyclosilicates and contains highly puckered twelve‐membered [Si₁₂O₃₆]‐rings centered on the . Five of the seven crystallographically independent alkaline and alkaline earth cations are surrounded by six oxygen ligands in the form of distorted octahedra, which share opposite triangular faces and form non‐intersecting columns parallel to the body diagonals of the cubic unit cell. This arrangement corresponds to one of the cubic cylinder or rod packings. The two remaining sites have more irregular coordination environments with eight next oxygen neighbors. High temperature X‐ray powder diffraction data have been collected to determine the thermal expansion of this material: between room temperature and 700 °C the coefficient of thermal expansion has a value of α = 12.9(2) × 10^?6 [°C^?1]. Single crystals of K₄BaSi₃O₉ have been obtained from the devitrification of a glass with the same composition. The structure was determined from a single crystal diffraction data set collected at ?100 °C and refined to a final R index of 0.0298 for 1288 observed reflections (I > 2σ(>I)). The compound is isostructural with modification II of K₄SrSi₃O₉. Basic crystallographic data are as follows: space group Ama2, a = 11.0695(15) Å, b = 8.0708(10) Å, c = 11.905(2) Å, V = 1063.6(3) ų, Z = 4. With respect to the silicate anions the material can be classified as a sechser single chain silicate. The crankshaft‐like chains run parallel to [100] and are linked by K and Ba cations, which are distributed among five crystallographically independent sites. The coordination polyhedra of two of the non‐tetrahedral cations can be described by distorted octahedra sharing opposite triangular faces. They build non‐intersecting columns parallel to [011] and [0‐11], respectively. The other sites exhibit more irregular coordination spheres with 7‐9 neighbours.     

Crystal structure of the pyrovanadate K4V2O7

The crystal structure of anhydrous K₄V₂O₇ (I) is determined by powder X-ray diffraction. The compound crystallizes in the monoclinic system (a = 10.222(1) Å, b = 6.2309(8) Å, c = 7.282(1) Å, β = 101.31(1)°, space group C2/m, Z = 2). The structure contains layers of isolated V₂O₇ pyrovanadate groups separated by layers of potassium cations. The hydration and dehydration of I are studied by thermal analysis and high-temperature X-ray diffraction. The dehydration is accompanied by decomposition of the starting crystal hydrate to give intermediate compounds. Anhydrous compound I undergoes a reversible phase transition at 740°C. The high-temperature phase is assumed to have a hexagonal unit cell (a = 6.169(4) Å, c = 15.72(1) Å, Z = 2).     

Syntheses,Characterizations, and Crystal Structures of Two New Organically Templated Borates

Two new organically templated borates, [H₂DAB][B₇O₉(OH)₅]·2H₂O ( 1 ) and [H₂DAB][B₇O₁₀(OH)₃] ( 2 ), have been synthesized under mild conditions in the presence of DAB acting as structure‐directing agent (DAB = 1,4‐diaminobutane). The structures were determined by single crystal X‐ray diffraction and further characterized by FTIR, elemental analysis, and thermogravimetric analysis. Both 1 and 2 crystallize in the same triclinic system, space group (No. 2); 1: a = 8.238(4) Å, b = 8.348 (5) Å, c = 14.574(8) Å, a = 101.050(3)°, β = 92.313(7)°, γ = 112.694(5)°, V = 900.3(8) ų, Z = 2; 2: a = 8.8769(3) Å, b = 9.3204(2) Å, c = 10.2204(5) Å, α = 74.474(2)°, β = 85.292(5)°, γ = 72.730(2)°, V = 778.01(5) ų, Z = 2. The structure of 1 consists of [B₇O₉(OH)₅]^2? groups, which represents the first example of organically templated heptaborate. The structure exhibits interesting hydrogen‐bonded network formed by borate polyanion [B₁₄O₂₀(OH)₆]^4?, which can be regarded as being constructed from the dehydration of the FBBs in 1 . The diprotonated organic amines are filled in the free space of the hydrogen‐bonded network and interact with the inorganic framework by extensive hydrogen bonds.     

Ca2Ga3MgN5 – A Highly Condensed Nitridogallate

The nitridogallate Ca₂Ga₃MgN₅ was obtained from reaction of the elements in sodium flux with Na‐azide at 760 °C in weld shut niobium ampoules. Crystal structure solution and refinement was carried out on the basis of single‐crystal X‐ray diffraction data. Ca₂Ga₃MgN₅ [space group C2/m (no. 12), a = 11.160(2), b = 3.2965(7), c = 8.006(2) Å, and β = 109.93(3)°, Z = 2] shows an anionic substructure made up of mixed (Mg/Ga)N₄ tetrahedra, which are sharing both common vertices and edges building a three‐dimensional network. The crystal structure of Ca₂Ga₃MgN₅ is related to known alkaline earth nitridosilicates (M^II₂Si₅N₈, M^II = Sr, Ba), but is significantly higher condensed due to additional edge‐sharing in the anionic substructure.     

Synthesis and Crystal Structure of SrFe[BP2O8(OH)2]

SrFe[BP₂O₈(OH)₂] was synthesised under mild hydrothermal conditions. The crystal structure was determined from single–crystal X–ray diffraction data: triclinic, space group P (No. 2), a = 6.6704(12) Å, b = 6.6927(13) Å, c = 9.3891(19) Å, α = 109.829(5)°, β = 102.068(6)°, γ = 103.151(3)°, V = 364.74(12) ų and Z = 2. The crystal structure of SrFe[BP₂O₈(OH)₂] contains isolated borophosphate oligomers, [BP₂O₈(OH)₂]^5–, which are interconnected by Fe^IIIO₄(OH)₂ coordination octahedra. The resulting three–dimensional framework is characterised by elliptical channels running along [011]. Strontium takes positions inside the channels.     

Darstellung,Kristallstruktur und Eigenschaften von Ln3AuO6 (Ln = Sm,Eu, Gd)

Syntheses, Crystal Structures, and Properties of Ln₃AuO₆ (Ln = Sm, Eu, Gd) The title compounds have been prepared from amorphous Au₂O₃ · x H₂O (x = 1–3) and Ln₂O₃ (Ln = Nd, Sm, Eu) via solid state reaction under elevated oxygen pressure adding KOH as mineralizing agent. They crystallize in a new structure type (triclinic, P1, Z = 1, Sm₃AuO₆: a = 3.7272(2) Å, b = 5.6311(2) Å, c = 7.0734(3) Å, α = 90.32(2)°, β = 103.983(3)°, γ = 90.822(2)°, 125 powder intensities, R_p = 2.57%, Eu₃AuO₆: a = 3.7012(2) Å, b = 5.6134(2) Å, c = 7.0652(4) Å, α = 90.838(3)°, β = 102.956(3)°, γ = 90.909(2)°, 122 powder intensities, R_p = 3.16%, Gd₃AuO₆: a = 3.6720(2) Å, b = 5.5977(2) Å, c = 7.0636(2) Å, α = 90.509(2)°, β = 102.889(3)°, γ = 91.068(2)°, 3424 reflections, R₁ = 12.90%). The crystal structure was solved and refined from single crystal data of Gd₃AuO₆. The structures of Sm₃AuO₆ and Eu₃AuO₆ were refined from powder diffraction data. The isolated square planar AuO₄ units are stacked along the a‐axis and are linked by LnO₆‐ and LnO₆₊₁‐polyhedra. One of the oxygen atoms is exclusively coordinated by trivalent lanthanides, in tetrahedral geometry. The lanthanoid aurates decompose between 700 and 900 °C into Ln₂O₃, Au and O₂. The magnetic moments μ_eff(Gd₃AuO₆) = 7.9 μ_B and, at 20 °C respectively, μ_eff(Sm₃AuO₆) = 1.55 μ_B as well as μ_eff(Eu₃AuO₆) = 3.5 μ_B confirm that the lanthanides are trivalent. The UV/VIS absorption spectra can be interpreted at assuming free ions.     

Synthesis,Single Crystal Growth and Crystal Structure of Ta7Cu10Ga34 – a 8 × 4 × 2 Super Structure of CsCl

Single crystals of Ta₇Cu₁₀Ga₃₄ were grown from the elements in a Cu/Ga melt. Ta₇Cu₁₀Ga₃₄ represents the first ternary compound of the system Ta/Cu/Ga. The crystal structure (Cmmm, oC102, Z = 2, a = 23.803(1), b = 12.2087(4), c = 5.7487(2) Å, 1291 refl. 78 parameters, R₁ = 0.037, wR₂ = 0.070). The crystal structure is characterized by rods of pentagonal prisms MGa₁₀, which are alternatingly occupied by Ta and Cu. Four of these rods are connected to columns running in direction (001). These columns are linked by cubic units TaGa₈, CuGa₈, and GaGa₈. According to the characteristic structural elements and the size of the unit cell Ta₇Cu₁₀Ga₃₄ represents a 8 × 4 × 2 super structure of CsCl or bcc. With respect to the underlying CsCl structure the formula can be written as [Ta₇Cu₁₀Ga₂□₁₃]Ga₃₂, i.e. a cubic primitive packing of 32 Ga atoms with Ta, Cu, and Ga in cubic voids and 13 vacancies. The pentagonal‐prismatic coordination of Ta and Cu can formally be obtained from the cubic primitive packing of Ga atoms by a 45° rotation of a part of the Ga₈ cubes. There is a close similarity to the binary compounds Ta₈Ga₄₁ and Ta_2–xGa_5+x. The first one is also related to a CsCl‐like structure, the latter one contains rods of pentagonal prisms, which form the same columns. There are also relations to the ternaries V₂Cu₃Ga₈ and V₁₁Cu₉Ga₄₆, whose cubic structures are more or less complex variants of CsCl.     

Evidence for the Solid State Structural Transformation of the Network-Type Decavanadate (NC7H14)4[H2V10O28] into a Lamellar Topology (NC7H14)[V4O10]

The hydrothermal synthesis and the structural determinations of two vanadium oxides interleaved by quinuclidinium cations are described; (NC₇H₁₄)₄[H₂V₁₀O₂₈] is an anhydrous diprotonated decavanadate (triclinic, P 1 (n° 2), a = 9.701(1) Å, b = 10.839(1) Å, c = 12.7566(2) Å, α = 109.13(1)°, β = 112.09(1)°, γ = 92.17(2)°) and (NC₇H₁₄)[V₄O₁₀] a layered compound (orthorhombic, C mcm (n° 63), a = 18.4461(5) Å, b = 6.6619(2) Å, c = 11.7967(2) Å). Thermodiffractometry shows that the decavanadate irreversibly transforms at 230 °C into the layered compound without any amorphous intermediate state.     

Die isotypen Verbindungen BaRh2Si2, BaIr2Si2 und BaPt2Ga2 – eine monokline Verzerrungsvariante der CaRh2B2-Struktur

The Isotypic Compounds BaRh₂Si₂, BaIr₂Si₂, and BaPt₂Ga₂ – a Monoclinic Distortion Variant of the CaRh₂B₂ Structure The new compounds BaRh₂Si₂ (monoclinic, P2₁/c, a = 792.6(1) pm, b = 664.5(7) pm, c = 767.9(4) pm, β = 91.2(1)°, Z = 4, 2867 reflexions, 47 parameters, R = 0.024), BaIr₂Si₂ (monoclinic, P2₁/c, a = 792.47(6) pm, b = 664.28(6) pm, c = 772.22(6) pm, β = 92.181(7)°, Z = 4, 1939 reflexions, 47 parameters, R = 0.037) and BaPt₂Ga₂ (monoclinic, P2₁/c, a = 850.4(1) pm, b = 647.3(1) pm, c = 819.8(1) pm, β = 95.97(1)°, Z = 4, 1506 reflexions, 47 parameters, R = 0.038) were prepared by reaction of the elements. Their structures were determined from single crystal data. The compounds crystallize isotypically with a distortion variant of the CaRh₂B₂ type of structure.     

Crystal Structures of Alkali Metal Peroxodiphosphates

Peroxodiphosphates of alkali metals can be prepared from K₄P₂O₈, which is synthesized by electrolysis, in metathesis reactions with the corresponding perchlorates. Single crystals have been obtained by diffusion of methanol into aqueous solutions of the peroxodiphosphates. The crystal structures of Li₄P₂O₈·4H₂O (P2₁/n; a = 8.057(2) Å, b = 5.074(1) Å, c = 12.288(3) Å, β = 100.53(2)°; V = 493.9(2) ų; Z = 2), Na₄P₂O₈·18H₂O (at 130 K: P6₁; a = 9.0984(14) Å, c = 49.926(13) Å; V = 3579.2(12) ų; Z = 6) and K₄P₂O₈ (P2₁/c; a = 5.9041(15) Å, b = 10.254(2) Å, c = 7.356(2) Å, β = 99.05(3)°; V = 439.79(18) ų; Z = 2) have been determined by X‐ray diffraction. In the Li salt the cations are tetrahedrally coordinated by one water molecule and three oxygen atoms of the anions, whereas the Na salt is characterized by binuclear [Na₂(H₂O)₉]²⁺ complexes. At low temperatures, the latter undergoes a phase transition from a structure with disordered anions to a completely ordered phase. K₄P₂O₈ is solvent‐free and exhibits irregular cation coordination. The structure of the peroxodiphosphate anion is very similar in all compounds; the mean O–O distance is 1.49(1) Å. In addition, the structure determination of K₄(HPO₄)₂·3H₂O₂ (P2₁/n; a = 6.076(1) Å, b = 6.579(1) Å, c = 17.215(2) Å, β = 99.73(1)°; V = 678.26(17) ų; Z = 2), which can be mistaken for K₄P₂O₈, is presented.     

Influence of the Counterions on the Structures of Ternary Zn/Sn/Se Anions: Synthesis and Properties of [Rb10(H2O)14.5][Zn4(μ4‐Se)2(SnSe4)4] and [Ba5(H2O)32][Zn5Sn(μ3‐Se)4(SnSe4)4]

Reactions of rubidium or barium salts of the ortho‐selenostannate anion, [Rb₄(H₂O)₄][SnSe₄] ( 1 ) or [Ba₂(H₂O)₅][SnSe₄] ( 2 ) with Zn(OAc)₂ or ZnCl₂ in aqueous solution yielded two novel compounds with different ternary Zn/Sn/Se anions, [Rb₁₀(H₂O)_14.5][Zn₄(μ₄‐Se)₂(SnSe₄)₄] ( 3 ) and [Ba₅(H₂O)₃₂][Zn₅Sn(μ₃‐Se)₄(SnSe₄)₄] ( 4 ). 1 – 4 have been determined by means of single crystal X‐ray diffraction: 1 : triclinic space group lattice dimensions at 203 K: a = 8.2582(17) Å, b = 10.634(2) Å, c = 10.922(2) Å, α = 110.16(3)°, β = 91.74(3)°, γ = 97.86(3)°, V = 888.8(3) ų; R₁ [I > 2σ(I)] = 0.0669; wR₂ = 0.1619; 2 : orthorhombic space group Pnma; lattice dimensions at 203 K: a = 17.828(4) Å, b = 11.101(2) Å, c = 6.7784(14) Å, V = 1341.5(5) ų; R₁ [I > 2σ(I)] = 0.0561; wR₂ = 0.1523; 3 : triclinic space group ; lattice dimension at 203 K: a = 17.431(4) Å, b = 17.459(4) Å, c = 22.730(5) Å, α = 105.82(3)°, β = 99.17(3)°, γ = 90.06(3)°, V = 6563.1(2) ų; R₁ [I > 2σ(I)] = 0.0822; wR₂ = 0.1782; 4 : monoclinic space group P2₁/c; lattice dimensions at 203 K: a = 25.231(5) Å, b = 24.776(5) Å, c = 25.396(5) Å, β = 106.59(3)°, V = 15215.0(5) ų; R₁ [I > 2σ(I)] = 0.0767; wR₂ = 0.1734. The results serve to underline the crucial role of the counterion for the type of ternary anion to be observed in the crystal. Whereas Rb⁺(aq) stabilizes a P1‐type Zn/Sn/Se supertetrahedron in 3 like K⁺, the Ba²⁺(aq) ions better fit to an anionic T3‐type Zn/Sn/Se cluster arrangement as do Na⁺ ions. It is possible to estimate a radius:charge ratio for the stabilization of the two structural motifs.     

CRYSTAL STRUCTURE OF THE ISOMORPHOUS COMPLEXES TETRAAQUABIS(2,6-DIHYDROXY-BENZOATO-O)(2,6-DIHYDROXY-BENZOATO-O,O)TERBIUM(III) AND HOLMIUM(III) DIHYDRATE

Abstract

The structures of isomorphic Tb(III) and Ho(III) complexes with 2,6-dihydroxybenzoic acid of formula [Tb(C₇H₅O₄] 2H₂O and [Ho(C₇H₅O₄)₃ 4H₂O] 2H₂O has been determined by X-ray diffraction and refined to a residual R = 0.030 for 5376 observed reflections and R = 0.0284 for 5660 observed reflections, for Tb(III) and Ho(III) complexes, respectively. Crystals are triclinic, space group P1 with a= 10.748(2), b=11.309(2), c = 12.452(2)Å, α = 82.28(3), ? = 73.05(5), γ = 68.27(3)° for Tb(III) and a= 10.731(2), b=11.269(2), c = 12.436(2)Å, α = 82.25(3), β = 72.92(3), γ = 68.46(3)° for Ho(III).

In the structure of these monomelic complexes the metal ions are coordinated by oxygen atoms of one bidentate chelating and two monodentate carboxylate groups and four molecules of water. Tb-O distances are in the range 2.323(3)-2.506(3) Å and Ho-0 2.297(3)-2.486(3) Å. The crystal structure, consisting of discrete units of neutral complexes with two molecules of water of crystallization is stabilized by intra-and intermolecular hydrogen bonds.     

The Crystal Structure of InGaO3(ZnO)4: A Single Crystal X‐ray and Electron Diffraction Study

The crystal structure of the mixed oxide InGaO₃(ZnO)₄ has been determined from electron diffraction and single‐crystal X‐ray diffraction data. The compound crystallises in a hexagonal space group (P6₃/mmc; No. 194), deduced from convergent beam electron diffraction (CBED). Single crystals of InGaO₃(ZnO)₄ were grown from a K₂MoO₄ flux in sealed platinum tubes. Single crystal structure refinement from XRD data [a = 3.2850(2) Å; c = 32.906(3) Å; Z = 2; 4232 data, R₁ = 0.0685] reveals a compound with oxygen anions forming a closest‐packed arrangement. Within this packing In³⁺ cations occupy octahedral interstices, forming layers of edge sharing octahedra. In between these layers are regions with composition [Zn₄GaO₅]⁺ forming a wurtzite type of structure. Inversions of the ZnO₄ tetrahedra occurs (i) at the InO₆ octahedral layer and (ii) halfway in the wurtzite type region, where the inversion boundary is built by Ga³⁺ in trigonal bipyramidal coordination with a long Ga–O_apical distance of 2.19(1) Å. The site occupation of Zn²⁺ and Ga³⁺, respectively, was confirmed by bond valence sum calculations. The compounds described here have the same structural charactistics as other known members with general formula ARO₃(ZnO)_m with m = integer.     

Rietveld Analysis of a High Pressure Modification of Monocalcium Oxogallate (CaGa2O4)

A high‐pressure modification of monocalcium gallate (CaGa₂O₄) has been prepared in a piston‐cylinder apparatus at 700 °C and 4.0 GPa. The compound is orthorhombic (space group Pnam, a = 9.12476(15) Å, b = 10.56093(18) Å, c = 2.98547(4) Å, V = 287.70(1) ų, Z = 4, D_calc = 5.62 g/cm³) and belongs to the CaFe₂O₄‐type structure family. The structure was refined by the Rietveld method using laboratory X‐ray powder diffraction data. Two crystallographically independent GaO₆‐octahedra forming edge‐sharing double chains can be distinguished. The shared edges exhibit a considerable shortening. The chains are running parallel to the c‐axis and are linked by corner‐sharing. They enclose tunnels in which the calcium atoms are located for charge compensation. Each calcium cation has eight nearest oxygen neighbors. The coordination environment can be described as a bicapped trigonal prism.     

Synthesis and Crystal Structure of K6.5H4.5[CeK2(SiW11O39)2]·26H2O

The title compound, K_6.5H_4.5[CeK₂(SiW₁₁O₃₉)₂]·26H₂O was prepared and its structure characterized by IR and single crystal X-ray structural analysis. It belongs to triclinic, space group P1 with a = 12.719(3) Å, b = 16.658(4) Å, c = 23.075(6) Å, α = 94.41(2)°, β = 98.90(2)°, γ = 92.40(2)°; V = 4809(2) Å^?3, Z = 2, Dc = 4.344 g cm^?3, μ = 27.170 mm^?1, F (000) = 5519. The results show that the cerium and two potassium atoms link the two anionic units SiW₁₁O^8? ₃₉ through O-Ce-O and O-K-O bridges and construct the double 1 : 11 series heteropolytungstate. Furthermore, cerium is coordinated to eight oxygen atoms (four O_c and four O_b) from two tetradentate SiW₁₁O^8? ₃₉ ligands forming a square anti-prism. The coordination numbers for K1 and K2 are 8 and 7, respectively.