Structure, crystal chemistry and thermal evolution of the δ-Bi2O3-related phase Bi9ReO17

The thermal evolution and structural properties of fluorite-related δ-Bi₂O₃-type Bi₉ReO₁₇ were studied with variable temperature neutron powder diffraction, synchrotron X-ray powder diffraction and electron diffraction. The thermodynamically stable room-temperature crystal structure is monoclinic P2₁/c, a=9.89917(5), b=19.70356(10), c=11.61597(6) Å, β=125.302(2)° (R_p=3.51%, wR_p=3.60%) and features clusters of ReO₄ tetrahedra embedded in a distorted Bi–O fluorite-like network. This phase is stable up to 725 °C whereupon it transforms to a disordered δ-Bi₂O₃-like phase, which was modeled with δ-Bi₂O₃ in cubic Fm3¯m with a=5.7809(1) Å (R_p=2.49%, wR_p=2.44%) at 750 °C. Quenching from above 725 °C leads to a different phase, the structure of which has not been solved but appears on the basis of spectroscopic evidence to contain both ReO₄ tetrahedra and ReO₆ octahedra.     

Synthesis and characterization of [Zn(2,2′-bipy)]2(H2PO3)4: A neutral zinc phosphite cluster containing ZnO3N2 and H2PO3 units

The hydrothermal synthesis, crystal structure and some properties of a zinc phosphite with a neutral cluster, [Zn(2,2′-bipy)]₂(H₂PO₃)₄, are reported. This compound crystallizes in the triclinic system of space group P-1 (No. 2), a=8.3067(5) Å, b=8.9545(4) Å, c=10.0893(6) Å, α=95.448(2)°, β=99.7530(10)°, γ=103.461(2)°, V=712.23(7) ų, Z=1. The cluster consists of 4-membered rings formed by alternating ZnO₃N₂ square pyramids and H₂PO₃ pseudo pyramids, with two “hanging” H₂PO₃ groups attached to each of the Zn centers. The clusters are linked together by extensive multipoint hydrogen bonding involving the phosphite units to form a sheet-like structure. This compound represents the first example of zinc phosphite with P---OH bonds. An intense photoluminescence was observed from this compound upon photoexcitation at 388 nm.     

The Phase Relations in the System In2O3–TiO2–MgO at 1100 and 1350°C

The phase relations in the system In₂O₃–TiO₂–MgO at 1100 and 1350°C are determined by a classical quenching method. In this system, there are four pseudobinary compounds, In₂TiO₅, MgTi₂O₅ (pseudobrookite type), MgTiO₃ (ilmenite type), and Mg₂TiO₄ (spinel type) at 1100°C. At 1350°C, in addition to these compounds there exist a spinel-type solid solution Mg_2−xIn_2xTi_1−xO₄ (0≤x≤1) and a compound In₆Ti₆MgO₂₂ with lattice constants a=5.9236(7) Å, b=3.3862(4) Å, c=6.3609(7) Å, β=108.15(1)°, and q=0.369, which is isostructural with the monoclinic In₃Ti₂FeO₁₀ in the system In₂O₃–TiO₂–MgO. The relation between the lattice constants of the spinel phase and the composition nearly satisfies Vegard's law. In₆Ti₆MgO₂₂ extends a solid solution range to In₂₀Ti₁₇Mg₃O₆₇ with lattice constants of a=5.9230(5) Å, b=3.3823(3) Å, c=6.3698(6) Å, β=108.10(5)°, and q=0.360. The distributions of constituent cations in the solid solutions are discussed in terms of their ionic radius and site preference effect.     

Novel M(II)–Hg(II) coordination polymers generated from metal-containing building blocks M(2-pyrazinecarboxylate)2 · (H2O)2 (M=Cu, Ni, Co) and HgCl2

A new class of M(II)–Hg(II) (M=Cu(II), Co(II), Ni(II)) mixed-metal coordination polymers, Cu(2-pyrazinecarboxylate)₂HgCl₂ (4), [Co(2-pyrazinecarboxylate)₂(HgCl₂)₂] · 0.61H₂O (5) and [Ni(2-pyrazinecarboxylate)₂(HgCl₂)₂] · 0.77H₂O (6), have been prepared by self assembly of metal-containing building blocks, M(2-pyrazinecarboxylate)₂ · (H₂O)₂(M=Cu(II), Co(II), Ni(II)), with HgCl₂. Compounds 4–6 were characterized fully by IR, elemental analysis and single crystal X-ray diffraction. Compound 4 crystallized in the monoclinic space group C2/c, with a=17.916(5) Å, b=7.223(2) Å, c=13.335(4) Å, β=128.726(3)°, V=1346.2(6) ų, Z=4. It contains alternating Hg(II) and Cu(II) metal centers that are cross-linked by 2-pyrazinecarboxylate spacers and chlorine co-ligands to generate a unique three-dimensional Hg(II)–Cu(II) mixed metal framework. Compound 5 crystallized in the triclinic space group P , with a=6.3879(7) Å, b=6.6626(8) Å, c=13.2286(15) Å, α=96.339(2)°, β=91.590(2)°, γ=113.462(2)°, V=511.71(10) ų, Z=1. Compound 6 also crystallized in the triclinic space group P , with a=6.3543(8) Å, b=6.6194(8) Å, c=13.2801(16) Å, α=96.449(2)°, β=92.263(2)°, γ=113.541(2)°, V=506.67(11) ų, Z=1. Compounds 5 and 6 are isostructural and in the solid state the Hg(II)M(II)Hg(II) units are connected by Hg₂Cl₂ linkages to produce a novel M(II)–Hg(II) (M=Co(II), Ni(II)) zigzag mixed-metal chain, in which a new type of M–M′–M′–M array was observed. The metal containing building blocks, M(2-pyrazinecarboxylate)₂ · (H₂O)₂ (M=Cu(II), Co(II), Ni(II)), exhibit different connectivities to HgCl₂ depending on the metal cation contained within them.     

The crystal structure, vibrational spectra, and thermal behavior of dilithium piperazinium(2+) selenate tetrahydrate and dilithium N,N′-dimethylpiperazinium(2+) selenate tetrahydrate

The crystal structure of dilithium piperazinium(2+) selenate tetrahydrate has been solved; this substance crystallizes in the triclinic space group , a=7.931(2) Å, b=7.974(2) Å, c=7.991(2) Å, α=106.99(2)°, β=101.83(2)°, γ=119.28(2)° Z=1, R=0.0280 for 1489 observed reflections. A similar compound, dilithium N,N′-dimethylpiperazinium(2+) selenate tetrahydrate crystallizes in a monoclinic system with space group P2₁/c and lattice parameters a=7.338(1) Å, b=8.792(2) Å, c=12.856(1) Å, β=92.04(2)°, Z=2, R=0.0334 for 1462 observed reflections. Both structures are centrosymmetric with center of symmetry in the center of eight membered ring formed with two SeO₄ tetrahedra and two LiO₄ tetrahedra connected through tops. The two remaining oxygens on each Li atom come from water molecules. The FTIR and FT Raman spectra of both natural and N,O-deuterated substances have been measured and studied. The thermoanalytical properties were studied using TG, DTG and DTA methods in the temperature range 293–873 K for piperazinium derivative and in the range 293–523 K for dimethylpiperazinium derivative. DSC measurements were carried out in the temperature range 95–343 K. No phase transition was found in this temperature region for either of the compounds.     

Syntheses and characterization of two oxoborates, (Pb3O)2(BO3)2MO4 (M=Cr, Mo)

Two oxoborates, (Pb₃O)₂(BO₃)₂MO₄ (M=Cr, Mo), have been prepared by solid-state reactions below 700 °C. Single-crystal XRD analyses showed that the Cr compound crystallizes in the orthorhombic group Pnma with a=6.4160(13) Å, b=11.635(2) Å, c=18.164(4) Å, Z=4 and the Mo analog in the group Cmcm with a=18.446(4) Å, b=6.3557(13) Å, c=11.657(2) Å, Z=4. Both compounds are characterized by one-dimensional chains formed by corner-sharing OPb₄ tetrahedra. BO₃ and CrO₄ (MoO₄) groups are located around the chains to hold them together via Pb–O bonds. The IR spectra further confirmed the presence of BO₃ groups in both structures and UV–vis diffuse reflectance spectra showed band gaps of about 1.8 and 2.9 eV for the Cr and Mo compounds, respectively. Band structure calculations indicated that (Pb₃O)₂(BO₃)₂MoO₄ is a direct semiconductor with the calculated energy gap of about 2.4 eV.     

Hydrothermal Synthesis and Crystal Structure of [(CH3NH3)1.03K2.97]Sb12S20·1.34H2O

A novel thioantimonate(III) [(CH₃NH₃)_1.03K_2.97]Sb₁₂S₂₀·1.34H₂O was synthesized hydrothermally. It crystallizes in space groupP , witha=11.9939(7) Å,b=12.8790(8) Å,c=14.9695(9) Å,α=100.033(1)°,β=99.691(1)°,γ=108.582(1)°,V=2095.3(2) ų, andZ=2. The structure is determined from single crystal X-ray diffraction data collected at room temperature and refined toR(F)=0.037. In the crystal structure, each Sb(III) atoms has short bonds (2.37–2.58 Å) to three S atoms. The pyramidal [SbS₃] groups share common S atoms forming two types of centrosymmetric [Sb₁₂S₂₀] rings with the same topology. These rings are interconnected by weaker Sb–S bonds (2.92–3.29 Å) into 2-dimensional layers. Adjacent layers are parallel with K⁺and CH₃NH⁺₃ions and H₂O molecules located between them. Variation of bond valence sums calculated for the Sb(III) cations is found to be correlated with the coordination geometry. This is interpreted as due to the stereochemical activity of their lone electron pairs.     

High-pressure preparation, crystal structure, and properties of the new rare-earth oxoborate β-Dy2B4O9

In this work we report about a new rare-earth oxoborate β-Dy₂B₄O₉ synthesized under high-pressure/high-temperature conditions from Dy₂O₃ and boron oxide B₂O₃ in a B₂O₃/Na₂O₂ flux with a walker-type multianvil apparatus at 8 GPa and 1000°C. Single crystal X-ray structure determination of β-Dy₂B₄O₉ revealed: , a=616.2(1) pm, b=642.8(1) pm, c=748.5(1) pm, α=102.54(1)°, β=97.08(1)°, γ=102.45(1)°, Z=2, R1=0.0151, wR₂=0.0475 (all data). The compound exhibits a new structure type which is built up from bands of linked BO₃- (Δ) and tetrahedral BO₄-groups (□). The Dy³⁺-cations are positioned in the voids between the bands. According to the conception of fundamental building blocks β-Dy₂B₄O₉ can be classified with the notation 2Δ6□:Δ3□=4□=3□Δ. Furthermore we report about temperature-resolved in situ powder diffraction measurements and IR-spectroscopic investigations on β-Dy₂B₄O₉.     

Synthesis, crystal structures, phase transition characterization and thermal decomposition of a new dabcodiium hexaaquairon(II) bis(sulfate): (C6H14N2)[Fe(H2O)6](SO4)2

The crystal structures of 1,4-diazabicyclo[2.2.2]octane (dabco)-templated iron sulfate, (C₆H₁₄N₂)[Fe(H₂O)₆](SO₄)₂, were determined at room temperature and at −173 °C from single-crystal X-ray diffraction. At 20 °C, it crystallises in the monoclinic symmetry, centrosymmetric space group P2₁/n, Z=2, a=7.964(5), b=9.100(5), c=12.065(5) Å, β=95.426(5)° and V=870.5(8) ų. The structure consists of [Fe(H₂O)₆]²⁺ and disordered (C₆H₁₄N₂)²⁺ cations and (SO₄)²⁻ anions connected together by an extensive three-dimensional H-bond network. The title compound undergoes a reversible phase transition of the first-order at −2.3 °C, characterized by DSC, dielectric measurement and optical observations, that suggests a relaxor–ferroelectric behavior. Below the transition temperature, the compound crystallizes in the monoclinic system, non-centrosymmetric space group Cc, with eight times the volume of the ambient phase: a=15.883(3), b=36.409(7), c=13.747(3) Å, β=120.2304(8)°, Z=16 and V=6868.7(2) ų. The organic moiety is then fully ordered within a supramolecular structure. Thermodiffractometry and thermogravimetric analyses indicate that its decomposition proceeds through three stages giving rise to the iron oxide.     

Synthesis, structure characterization and fluorescence property of a new fluoride borate crystal, CdZn2KB2O6F

A new fluoride borate crystal, CdZn₂KB₂O₆F, has been synthesized by flux-supported solid-state reaction. The crystal structure has been determined by single-crystal X-ray diffraction. It crystallizes in the trigonal space group with a=5.0381(6) Å, b=5.0381(6) Å, c=15.1550(19) Å, α=90.00°, β=90.00°, γ=120.00°, Z=2. The crystal represents a new structure type in which ZnBO₃ layers are connected through bridging fluorine and cadmium atoms alternately along the c-axis. K⁺ cations are filled in the intralayer open channels to balance charge. IR and Raman spectra further confirm the crystal structure. Photoluminescent measurement reveals that CdZn₂KB₂O₆F exhibits blue fluorescence at room temperature in the solid-state.     

Syntheses and characterization of Co(pydc)(H2O)2 and Ni(pydc)(H2O) (pydc = 3,5-pyridinedicarboxylate)

The hydrothermal reaction of 3,5-pyridinedicarboxylic acid (pydcH₂) and Co(NO₃)₂ or Ni(NO₃)₂ in the presence of 4,4′-bipyridine results in two novel compounds Co(pydc)(H₂O)₂ (1) and Ni(pydc)(H₂O) (2). Crystal data: 1, monoclinic, C2/c, a=9.900(2), b=11.984(2), c=7.3748(15) Å, β=105.37(3)°, V=843.7(3) Å³, Z=4; 2, monoclinic, P2₁/c, a=7.7496(6), b=15.0496(11), c=6.4224(5) Å, β=108.437(1)°, V=710.59(9) Å³, Z=4. The structure of 1 is composed of honeycomb layers built up from {CoO₄N} trigonal bipyramids and 3,5-pyridinedicarboxylate bridges. The structure of 2 adopts a three-dimensional framework structure in which the Ni atoms are coordinated by the pydc bridges both within the honeycomb layer and between the layers. The magnetic properties of 1 and 2 have been investigated.     

Syntheses, crystal structures and spectroscopic properties of KEu[AsS4], K3Dy[AsS4]2 and Rb4Nd0.67[AsS4]2

Three rare earth compounds, KEu[AsS₄] (1), K₃Dy[AsS₄]₂ (2), and Rb₄Nd_0.67[AsS₄]₂ (3) have been synthesized employing the molten flux method. The reactions of A₂S₃ (A = K, Rb), Ln (Ln = Eu, Dy, Nd), As₂S₃, S were accomplished at 600 °C for 96 h in evacuated fused silica ampoules. Crystal data for these compounds are: 1, monoclinic, space group P2₁/m (no. 11), a = 6.7276(7) Å, b = 6.7190(5) Å, c = 8.6947(9) Å, β = 107.287(12)°, Z = 2; 2, monoclinic, space group C2/c (no. 15), a = 10.3381(7) Å, b = 18.7439(12) Å, c = 8.8185(6) Å, β = 117.060(7)°, Z = 4; 3, orthorhombic, space group Ibam (no. 72), a = 18.7333(15) Å, b = 9.1461(5) Å, c = 10.2060(6) Å, Z = 4. 1 is a two-dimensional structure with ²_∞[Eu(AsS₄)]⁻ layers separated by potassium cations. Within each layer, distorted bicapped trigonal [EuS₈] prisms are linked through distorted [AsS₄]³⁻ tetrahedra. Each Eu²⁺ cation is coordinated by two [AsS₄]³⁻ units by edge-sharing and bonded to further two [AsS₄]³⁻ units by corner-sharing. Compound 2 contains a one-dimensional structure with ¹_∞[Dy(AsS₄)₂]³⁻ chains separated by potassium cations. Within each chain, distorted bicapped trigonal prisms of [DyS₈] are linked by slightly distorted [AsS₄]³⁻ tetrahedra. Each Dy³⁺ ion is surrounded by four [AsS₄]³⁻ moieties in an edge-sharing fashion. For compound 3 also a one-dimensional structure with ¹_∞[Nd₀.₆₇(AsS₄)₂]⁴⁻ chains is observed. But the Nd position is only partially occupied and overall every third Nd atom is missing along the chain. This cuts the infinite chains into short dimers containing two bridging [As₄]³⁻ units and four terminal [AsS₄]³⁻ groups. 1 is characterized with UV/vis diffuse reflectance spectroscopy, IR, and Raman spectra.     

[{(NiOH)2Mo10O36(PO4)Ti2}n]: a novel chainlike trimetal heteropolyanion based on pseudo-keggin fragments

A new mixed Mo/Ni/Ti heteropoly compound [C₅H₅NH]₅ [(NiOH)₂Mo₁₀O₃₆(PO₄)Ti₂] has been hydrothermally synthesized and structurally determined by the single-crystal X-ray diffraction. Black prismatic crystals crystallize in the monoclinic system, space group P2(1)/n, a=11.2075(2), b=37.8328(5) c=13.0888(1) Å, β=101.4580(10)°, M=2276.13, V=5439.19(13) ų, Z=4. Data were collected on a Siemens SMART CCD diffractometer at 293(2) K in the range of 1.68<θ<25.09° using the ω-scan technique (λ=0.71073 Å R(F)=0.0872 for 9621 reflections). The title compound contains a trimetal heteropolyanion polymer and “trans-titanium”-bridging pseudo-Keggin fragments linked to a chain.     

Synthesis and crystal structure of the high-pressure iron borate α-FeB2O4

The high-pressure iron borate α-FeB₂O₄ was synthesized under high-pressure and high-temperature conditions in a Walker-type multianvil apparatus at 7.5 GPa and 1100 °C. The monoclinic iron borate crystallizes with eight formula units in the space group P2₁/c with the lattice parameters a=715.2(2), b=744.5(2), c=862.3(2) pm, and β=94.71(3)°. The compound is built up exclusively from corner-sharing BO₄-tetrahedra, isotypic to the monoclinic phases β-SrGa₂O₄, CaAl₂O₄-II, and CaGa₂O₄. Additionally, the structure is closely related to the orthorhombic compound BaFe₂O₄. The structure consists of layers of six-membered rings, which are interconnected to a three-dimensional network. The iron cations are coordinated by six and seven oxygen atoms. Next to synthesis and crystal structure of the new high-pressure borate, structural coherences to other structure types are discussed.     

X-ray diffraction studies and phase transformations of CeNbO4+δ using in situ techniques

Investigation of CeNbO_4±δ has revealed that the previously determined phase transformations should be revised. Whereas previous studies have indicated that a reduced tetragonal modification of CeNbO₄ is produced on heating in vacuum the present study shows no evidence for this phase transformation. In contrast, a monoclinic–tetragonal phase transformation on heating in air was observed, indicating that the high temperature phase (800 °C) was a stable, oxygen excess tetragonal phase with a similar structure to the Scheelite mineral, CaWO₄. Lattice parameters for this phase were calculated to be a=5.3839(1) Å and c=11.6168(3) Å.     

Phase diagram of the La–Si binary system under high pressure and the structures of superconducting LaSi5 and LaSi10

The La–Si binary phase diagram under a high pressure of 13.5 GPa was experimentally constructed. New superconducting silicides LaSi₅ and LaSi₁₀ were found, which have peritectic decomposition temperatures at 1000 and 750 °C, respectively. The single crystal X-ray structural analysis revealed that there are two polymorphs in LaSi₅. The α-form obtained by heating a molar mixture of LaSi₂ and 3 Si at about 700 °C or by a rapid cooling from 1000 °C under pressure crystallizes with the space group C2/m and the lattice parameters a=15.11(3), b=4.032(6), c=8.26(1) Å, and β=109.11(1)°. The β-form obtained by a slow cooling from 800–950 °C to 600 °C under pressure has the same space group but with slightly different lattice parameters, a=14.922(7), b=3.906(2), c=8.807(4) Å, and β=107.19(1)°. The β-form is formed during the incomplete transformation of the α-form on cooling, and has always been obtained as a mixture with the α-form. The compound can be characterized as a Zintl phase with a polyanionic framework with large tunnels running along the b axis hosting lanthanum ions. In the β-form, three of the five Si sites are disordered. The two polymorphs contain one dimensional sila-polyacene ribbons, Si ladder polymer, running along the b axis. The α-form showed superconductivity with the transition temperature T_c of 11.5 K. LaSi₁₀ crystallizes with the space group 6₃/mmc and the lattice parameters a=9.623(4), c=4.723(3) Å. It is composed of La containing Si₁₈ polyhedra (La@Si₁₈) of hexagonal beer-barrel shape, which form straight columns by stacking along the c-axis via face sharing. One-dimensional columns of La@Si₁₈ barrels are edge-shared, and bundled with infinite Si trigonal bipyramid chains via corner sharing. The Si atoms in the straight chains have a five-fold coordination. LaSi₁₀ became a superconductor with T_c=6.7 K. The ab initio calculation of the electric band structures showed that α-LaSi₅ and LaSi₁₀ are metallic, and the conduction electrons mainly come from Si-3p orbitals.     

The Crystal Structure, Vibrational Spectra, and Thermal Behavior of Piperazinium(2+) Selenate Monohydrate and N, N′-Dimethylpiperazinium(2+) Selenate Dihydrate

The crystal structure of piperazinium(2+) selenate monohydrate has been resolved; this substance crystallizes in the monoclinic space group P2₁/n, a=6.4586(8), b=11.8335(7), c=11.8065(7) Å, β=100.990(8)°; V=885.80(13) Å⁵, Z=4, R=0.0446 for 1556 observed reflections. A similar compound, N,N′-dimethylpiperazinium(2+) selenate dihydrate, crystallizes in a triclinic system with space group P and lattice parameters a=6.7370(8), b=7.9845(9), c=12.3802(12) Å, α=92.435(9)°, β=100.219(9)°, γ=114.699(10)°; V=590.34(11) ų, Z=2, R=0.0311 for 2071 observed reflections. While, in the former structure, the cations of piperazinium(2+) in the chair conformation are arranged roughly plane-parallel above one another, in the second substance, the N,N′-dimethylpiperazinium (2+) ions lie approximately perpendicularly above one another. The FTIR and FT Raman spectra of both test substances have been measured and studied. The thermoanalytical properties were studied using TG, DTG, and DTA methods in the temperature range 293–533 K. DSC measurements were carried out in the temperature range 95–343 K. No phase transition was found in this temperature region for either of the compounds.     

An XRPD ab-initio structural determination of La2RuO5

The crystal structure of a new oxide, La₂RuO₅, was determined ab initio using conventional laboratory X-ray powder diffraction. Combining X-ray and electron diffraction techniques, we found that the new phase crystallized in the monoclinic system with the space group P2₁/c (SG no.14) and the cell parameters a=9.1878(2) Å, b=5.8313(2) Å, c=7.9575(2) Å and β=100.773(2)° (V=418.8 ų, Z=4). The structural determination with the Patterson method and Fourier difference syntheses and the final Rietveld refinement were performed by means of the JANA2000 program. The structure is built up from the regular stacking of a two octahedra thick [LaRuO₄]_∞ zigzag perovskite slab and an original 3.4 Å thick [LaO]_∞ slab which constitutes the key feature of this new structure.     

New Layered Materials in the K–In–Ge–As System: K8In8Ge5As17and K5In5Ge5As14

Exploratory synthesis in the K–In–Ge–As system has yielded the unusual layered compounds K₈In₈Ge₅As₁₇(1) and K₅In₅Ge₅As₁₄(2), both of which contain In–Ge–As layers with interleaved potassium ions, Ge–Ge bonds, InAs₄tetrahedra, As–As bonds, and rows of Ge₂As₆dimers. Compound 1 has As₃groups, while compound 2 has infinite As ribbons on both faces of each layer. Unlike compound 1, compound 2 has substitutional defects where indium partially occupies each of the three independent germanium sites in the ratio of 1:5 for In:Ge. This partial occupancy makes 2 an electron-precise compound. The Ge(In)–Ge(In) bond of 2 is longer than the Ge–Ge bond of 1, and this bond lengthening effect was confirmed by performing DFT-MO calculations on the model compounds H₃Ge–GeH₃and H₃Ge–InH⁻₃. Possible implications of electron imprecise formulas determined by X-ray crystal structure determinations are discussed. Compound 1: space groupP2₁/cwitha=18.394 (8) Å,b=19.087 (7) Å,c=25.360 (3) Å,β=105.71 (2)°,V=8571 (4) ų, andD_calcd=4.45g/cm³forZ=4. Refinement on 4455 reflections yieldedR(R_w)=6.8%(7.8%). Compound 2: space groupC2/mwitha=40.00 (1) Å,b=3.925 (2) Å,c=10.299 (3),β=99.97 (2)°,V=1592 (1) ų, andD_calcd= 4.55g/cm³forZ=8. Refinement on 1206 reflections yieldedR(R_w)=5.6% (5.7%).     

Crystallographic and theoretical study of phenyl 2,3,4,6-tetra-O-acetyl-1-thio-α-D-mannopyranoside

The thiomannoside is a key intermediate in the synthesis of polymannosaccharide. But its crystallographic study has not been reported. X-ray crystal structure analysis shows that the crystal of phenyl 2,3,4,6-tetra-O-acetyl-1-thio-α-D-mannopyranoside is in orthorhombic system, has P2₁2₁2₁ space group. Its unit cell dimensions are a=9.1731(11), b=11.574(2), and c=21.199(3) Å, α=β=γ=90.00°, Z=4, V=2250.6(6) ų, D_c=1.300 g/cm³. The crystallographic study reveals that the thiomannoside is an α-anomer. Most interestingly, the structure provides an evidence of existing C–HO and C–HS intramolecular and intermolecular hydrogen bonds.