Über Oxidsulfide mit Åkermanitstruktur CaLaGa3S6O,SrLaGa3S6O,La2ZnGa2S6O und Sr2ZnGe2S6O

On Oxidesulfides of Åkermanitetype-Structure CaLaGa₃S₆O, SrLaGa₃S₆O, La₂ZnGa₂S₆O, and Sr₂ZnGe₂S₆O The oxide sulfides were prepared for the first time (space group and lattice constants see “Inhaltsübersicht”). The atomic positions were refined from single crystal X-ray data for CaLaGa₃S₆O and La₂ZnGa₂S₆O. Problems concerning the metal distribution on the crystallographic positions are discussed by comparing interatomic distances. The ratio c/a of the new compounds is compared with that of isotypic compounds from literature.     

Calcium and strontium thio­sulfate,CaS2O3·6H2O and SrS2O3·5H2O

In contrast to former morphological studies, the results presented here show that calcium(II) thio­sulfate hexahydrate, CaS₂O₃·6H₂O, crystallizes centrosymmetrically in the pinacoidal class (point group ). The structure is characterized by chains, parallel to [100], of alternating S₂O₃ and Ca(H₂O)₆O₂ groups sharing common O atoms. The composition of each chain link is [Ca(H₂O)₆(S₂O₃)]. The geometry is analysed and compared in detail with the structural features of monoclinic strontium(II) thio­sulfate pentahydrate, SrS₂O₃·5H₂O, which forms layers, parallel to (100), of alternating S₂O₃ and Sr(H₂O)₄O₅ groups connected via common O atoms and O–O edges. Each layer contains [Sr(H₂O)₃O(S₂O₃)]_∞ as the unique repeat unit.     

Preparation,Crystal Structure and Vibrational Spectra of Ca2P2O6·2H2O and [Ca(H2O)3(H2P2O6)]·0.5(C12H24O6)·H2O

The calcium salts Ca₂P₂O₆ · 2H₂O ( 1 ) and [Ca(H₂O)₃(H₂P₂O₆)] · 0.5(C₁₂H₂₄O₆) · H₂O ( 2 ) were prepared and structurally characterized by single‐crystal X‐ray diffraction. Compound 1 crystallizes in the orthorhombic space group Pbca and compound 2 in the monoclinic space group P2₁/n. The crystal structure of compound 1 consists of chains of edge‐sharing [CaO₇] polyhedra linked by hypodiphosphate(IV) anions to form a three‐dimensional network. The crystal structure of compound 2 consists of alternated layers of crown ether and water molecules and respective ionic units. Within the layers of ionic units the Ca²⁺ cations are octahedrally coordinated by three monodentate dihydrogenhypodiphosphate(IV) anions and three water molecules. The IR/Raman spectra of the title compounds were recorded and interpreted, especially with respect to the [P₂O₆]^4– and [H₂P₂O₆]^2– groups. The phase purity of 2 was verified by powder diffraction measurements.     

Magnesium Hexafluoridozirconates MgZrF6·5H2O,MgZrF6·2H2O,and MgZrF6: Structures,Phase Transitions,and Internal Mobility of Water Molecules

The MgZrF₆ · n H₂O (n = 5, 2 and 0) compounds were studied by the methods of X‐ray diffraction and ¹⁹F, MAS ¹⁹F, and ¹H NMR spectroscopy. At room temperature, the compound MgZrF₆ · 5H₂O has a monoclinic C‐centered unit cell and is composed of isolated chains of edge‐sharing ZrF₈ dodecahedra reinforced with MgF₂(H₂O)₄ octahedra and uncoordinated H₂O molecules and characterized by a disordered system of hydrogen bonds. In the temperature range 259 to 255 K, a reversible monoclinic ? two‐domain triclinic phase transition is observed. The phase transition is accompanied with ordering of hydrogen atoms positions and the system of hydrogen bonds. The structure of MgZrF₆ · 2H₂O comprises a three‐dimensional framework consisting of chains of edge‐sharing ZrF₈ dodecahedra linked to each other through MgF₄(H₂O)₂ octahedra. The compound MgZrF₆ belongs to the NaSbF₆ type and is built from regular ZrF₆ and MgF₆ octahedra linked into a three‐dimensional framework through linear Zr–F–Mg bridges. The peaks in ¹⁹F MAS spectra were attributed to the fluorine structural positions. The motions of structural water molecules were studied by variable‐temperature ¹H NMR spectroscopy.     

SrCl2 · 1/2 H2O und SrCl2 · H2O Röntgenographische,thermoanalytische, Raman- und IR-spektroskopische Untersuchungen

SrCI₂ · 1/2 H₂O and SrCl₂ · H₂O. X-ray, Thermalanalytical, Raman, and I. R. Data The formation of the new compound SrCI₂ · 1/2 H₂O was detected with help of high-temperature X-ray and high-temperature Raman measurements. Strontium chloride hemihydrate was prepared by dehydration of the higher hydrates in a water-vapour atmosphere of 1 bar at 165 °C. The Course of dehydration of SrCI₂ · 6 H₂O, and SrCI₂ · 2 H₂O is discussed. X-ray, i.r.-and Raman data of SrCI₂ · 1/2 H₂O and SrCl₂ · H₂O are reported. SrCI₂ · H₂O crystallizes ortho-rhombic in the BaCI₂ · H₂O type (space group Pnma) with a = 1088.1(1), b = 416.2(1), and c = 886.4(1) pm. The water modes of the hydrates as well as the force constants and bond energies of the hydrogen bridges are discussed.     

Darstellung und eigenschaften von CeTe2O6 und ThTe2O6, verbindungen mit einer neuen überstruktur des fluorit-typs

Preparation and Properties of CeTe₂O and ThTe₂O₆, Compounds with a New Superstructure of the Fluorite Type It is demonstrated that in the systems MO₂/TeO₂ (with M = Ce, Th), treated in air and at 600°C, only phases of composition MTe₂O₆ are formed. They pertains to the cubic crystal system and constitutes a new type of fluorite-superstructure. Different aspects of its crystal chemistry are commented and also the infrared spectra are recorded and briefly discussed.     

Preparation,Crystal Structure,Vibrational Spectra,and Thermal Behavior of Rb2H2P2O6·2H2O

Single crystals of Rb₂H₂P₂O₆ · 2H₂O could be obtained from aqueous solutions of hypodiphosphoric acid and rubidium carbonate. Its crystal structure was determined by X‐ray diffraction and it crystallizes in the monoclinic space group P2₁/c with Z = 4. The salt‐like title compound consists of [H₂P₂O₆]^2– units in staggered P₂O₆‐skeleton conformation, Rb⁺ cations, and H₂O molecules, held together by intermolecular hydrogen bonds of the type O ··· O. The vibrational spectra (IR/FIR and Raman) of the rubidium salt were recorded and an assignment of the vibrational modes is proposed based on the point group C_2h for the P₂O₆‐skeleton of the anion. The thermal behavior of Rb₂H₂P₂O₆ · 2H₂O is dominated by a complex TG decay indicating a simultaneous H₂O delivery coupled with a disproportionation of [H₂P₂O₆]^2–, what is also supported by Raman spectra of heated samples.     

Alkalimolybdotellurate: Darstellung und Kristallstruktur von Rb6[TeMo6O24] · 10H2O und Rb6[TeMo6O24] · Te(OH)6 · 6H2O

Alkaline Molybdotellurates: Preparation and Crystal Structures of Rb₆[TeMo₆O₂₄] · 10H₂O and Rb₆[TeMo₆O₂₄] · Te(OH)₆ · 6H₂O Single crystals of Rb₆[TeMo₆O₂₄] · 10 H₂O and Rb₆[TeMo₆O₂₄] · Te(OH)₆ · 6 H₂O, respectively, were grown from aqueous solution. Rb₆[TeMo₆O₂₄] · 10 H₂O possesses the space group P1 . The lattice dimensions are a = 963.40(13), b = 972.56(12), c = 1 056.18(13) pm, α = 97.556(10), β = 113.445(9), γ = 102.075(10)°; Z = 1, 2 860 reflections, 215 parameters refined, R_g = 0.0257. The centrosymmetrical [TeMo₆O₂₄]^6? anions are stacked parallel to [010]. Rb(2) is coordinated with one exception by water molecules only. Folded chains consisting of [TeMo₆O₂₄]^6? anions and Rb(2) coordination polyhedra which are linked to pairs represent the prominent structural feature. Rb₆[TeMo₆O₂₄] · Te(OH)₆ · 6 H₂O crystallizes monoclinically in the space group C2/c with a = 1 886.4(3), b = 1 000.9(1), c = 2 126.5(3) pm, and β = 115.90(1)°; Z = 4, 3 206 reflections, 240 parameters refined, R_g = 0.0333. It is isostructural in high extent with (NH₄)₆[TeMo₆O₂₄] · Te(OH)₆ · 7 H₂O. Hydrogen bonds between Te(OH)₆ molecules and [TeMo₆O₂₄]^6? anions establish infinite strands. The [TeMo₆O₂₄]^6? anions gather around Te(OH)₆ providing channel-like voids extending parallel to [001].     

Chromium‐based clinopyroxene‐type germanates NaCrGe2O6 and LiCrGe2O6 at 298 K

The structure analyses of sodium chromium digermanate, NaCrGe₂O₆, (I), and lithium chromium digermanate, LiCrGe₂O₆, (II), provide important structural information for the clinopyroxene family, and form part of our ongoing studies on the phase transitions and magnetic properties of clinopyroxenes. (I) shows C2/c symmetry at 298 K, contains one Na, one Cr (both site symmetry 2 on special position 4e), one Ge and three O‐atom positions (on general positions 8f) and displays the well known clinopyroxene topology. The basic units of the structure of (I) are infinite zigzag chains of edge‐sharing Cr³⁺O₆ octahedra (M1 site), infinite chains of corner‐sharing GeO₄ tetrahedra, connected to the M1 chains by common corners, and Na sites occupying interstitial space. (II) was found to have P2₁/c symmetry at 298 K. The structure contains one Na, one Cr, two distinct Ge and six O‐atom positions, all on general positions 4e. The general topology of the structure of (II) is similar to that of (I); however, the loss of the twofold symmetry makes it possible for two distinct tetrahedral chains, having different conformation states, to exist. While sodium is (6+2)‐fold coordinated, lithium displays a pure sixfold coordination. Structural details are given and chemical comparison is made between silicate and germanate chromium‐based clinopyroxenes.     

ZnTe6O13, a new ZnO–TeO2 phase

Our investigations into the ZnO–TeO₂ system have produced a new phase, zinc(II) hexatellurium(IV) tridecaoxide, ZnTe₆O₁₃, with trigonal (R) symmetry, synthesized by repeated heating and cooling to a maximum temperature of 1053 K. The asymmetric unit consists of a Zn atom coordinated in a distorted octahedral fashion by two unique tellurium(IV) oxide units that form trigonal–bipyramidal TeO₄ and TeO₃₊₁ corner‐ and edge‐shared polyhedra. Except for the Zn and an O atom, which occupy 6c positions, all atoms occupy 18f general positions.     

Enthalpies of crystallization of NaCl,KCl, LiCl·H2O,MgCl2 6H2O,CaCl2 6H2O and BaCl2·2H2O from aqueous solution at 298.15 K

The enthalpies of crystallization of NaCl, KCl, LiCl·H₂O, MgCl₂·6H₂O, CaCl₂·6H₂O and BaCl₂·2H₂O from aqueous solution were determined by means of different calculation methods on the basis of the earlier-measured differential and integral enthalpies of solution of the above salts. The obtained crystallization enthalpies are discussed and compared with the appropriate literature data.

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Zusammenfassung Es wurden die Kristallisationenthalpien des NaCl, KCl, LiCl·H₂O, MgCl₂·6H₂O, CaCl₂·6H₂O und BaCl₂·2H₂O aus wässerigen Lösungen bestirnt. Es wurden vorher gemessene differenzierte und integrale Enthalpien von oben genannten gelösten Salze ausgenutzt, bei denen verschiedene Berechnungsmethoden angewandt wurden. Die gewonenen Kristallisationenthalpien wurden mit entsprechenden Literaturangaben erörtert und vergliechen.

     

Ein ungewöhnliches H-Brückenbindungssystem in Rubidium-hydroxiddihydrat,RbOH · 2 H2O

An Unusual System of Hydrogen Bonds in Rubidium Hydroxide Dihydrate, RbOH · 2 H₂O RbOH · 2H₂O was obtained by the reaction of Rb with H₂O and dehydration of the resulting solution by concentrated sulfuric acid. The compound melts at 310 K. The structure was determined by X-ray single crystal methods: The H positions of H₂O were found. The structure consists of a threedimensional H-bonded network of H₂O molecules and OH^?ions. Hydroxide ions are acceptors for four protons of four adjacent water molecules with d(O? O) = 2×2.59 Å and 2×2.82 Å. Oxygen of OH-ions is disordered over a distance of 1.27 Å. Rb has 8 H₂O molecules as nearest neighbours, d(Rb? O) = 3.03 Å to 3.07 Å, OH^?ions are further removed with d(Rb? O) ≥ 3.45 Å.     

ZnTa2O6, ein neuer Vertreter des tri-α-PbO2-Typs (mit ergänzenden Daten über ZnNb2O6)

ZnTa₂O₆, a New Member of tri-α-PbO₂-Type (with Supplement Data about ZnNb₂O₆) For the first time single crystals of ZnTa₂O₆ were prepared and investigated by single crystal X-ray work. a = 4.702, b = 17.094, c = 5.070 Å, space group D?Pbcn. ZnTa₂O₆ shows [MO₆]-octahedra-chains with a typical metal distribution. 2/3 of these chains contain alternating Zn²⁺- and Ta⁵⁺-ions. For that reason ZnTa₂O₆ does not belong to the Columbitstructure but to the tri-α-PbO₂-type.     

Mössbauer-Messungen an Sn2O3

Mössbauer Studies on Sn₂O₃ Mössbauer data for ¹¹⁹Sn in Sn₂O₃ show this compound to contain bivalent and tetravalent tin. Whereas tin(IV) is coordinated in a similar way in Sn₂O₃ and SnO₂, a rather large quadrupole splitting indicates an environment of low symmetry for tin(II).     

Facile synthesis of O6-alkyl-, O6-aryl-, and diaminopurine nucleosides from 2'-deoxyguanosine

The 3',5'-bis-O-TBDMS derivative of 2'-deoxyguanosine can be converted to its O6-alkyl and O6-aryl ethers as well as to N6-substituted diaminopurine nucleosides in two simple steps. Also described is a novel, nonaqueous, one-step O6-desulfonylation method that leads to deprotection of the carbonyl moiety of 2'-deoxyguanosine.     

Three hexafluoridoiridates(IV), Ca[IrF6]·2H2O,Sr[IrF6]·2H2O and Ba[IrF6]

The structures of the hexafluoridoiridates(IV) of calcium, Ca[IrF₆]·2H₂O [calcium hexafluoridoiridate(IV) dihydrate], strontium, Sr[IrF₆]·2H₂O [strontium hexafluoridoiridate(IV) dihydrate], and barium, Ba[IrF₆] [barium hexafluoridoiridate(IV)], have been determined by single‐crystal X‐ray analysis. The first two compounds are isomorphous. Their metal cations are eight‐coordinated in a distorted square‐antiprismatic coordination environment, and their anions are represented by an almost ideal octahedron. These two structures can be described as frameworks in which all atoms occupy general positions. Sr[RhF₆] and Ba[RhF₆] have a different space group (, from powder diffraction data) but similar cell dimensions. The structures are very close to that of Ba[IrF₆]. The cation is in a cuboctahedral coordination. The metal atoms are located on special positions of symmetry, while the F atoms are in general positions.