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.     

[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.     

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.     

Adjustment of dimensionality in covalent frameworks formed by Co and rhenium cluster chalcocyanide [Re6S8(CN)6]

The synthesis and X-ray structure of a new cluster compound (Pr₄N)₂Co[Re₆S₈(CN)₆] · 6H₂O is reported. It crystallizes in orthorhombic symmetry, P2₁2₁2₁ space group with four formula units per unit cell. The following parameters were found: a = 17.942(9) Å, b = 17.979(4) Å, c = 16.344(8) Å, V=5272 0rA³, ρ_calc=2.607 g cm⁻¹; final R=0.0331. The compound was prepared by interaction of layered Cs₂Co[Re₆S₈(CN)₆] · 2H₂O with aqueous solution of Pr₄NBr. This interaction results in cleavage of covalently linked {Co(H₂O)₂Re₆S₈(CN)₆}_2α²⁻ sheets and in formation of isolated fragments {Co(H₂O)₅Re₆S₈(CN)₆}^u2−. Heating of (Pr₄N)₂Co[Re₆S₈(CN)₆] · 6H₂O results in elimination of two water molecules and in formation of (Pr₄N)₂Co[Re₆S₈(CN)₆] · 4H₂O containing infinite -Co(H₂O)₄-NC-Re₆S₈(CN) ₄-CN-Co(H₂O)₄-chains.     

Diamine incorporated compounds derived from polymeric nickel(II) fumarates and oxalates: Crystal structure, spectral and thermal properties of [Ni(en)3](O2CCHCHCO2)·3H2O and [Ni(en)3](O2CCO2)

Lewis-base mediated fragmentation of polymeric nickel(II) fumarate and oxalate are attempted using chelating σ-donor diamines like ethylenediamine (en) and 1,3-diaminopropane (dap) in various conditions which yielded [Ni(en)₃](fum)·3H₂O (1), [Ni(en)₃](ox) (2), [Ni(dap)₂(fum)] (3) and [Ni(dap)(ox)]·2H₂O (4). While 1 and 2 are molecular products each containing octahedral [Ni(en)₃]²⁺ moieties and the anionic dicarboxylate species, 3 and 4 are dap-incorporated polymeric products. The fumarate derivative 1 containing [Ni(en)₃]²⁺ moieties crystallizes in the monoclinic space group C2/c with a = 17.899(4) Å, b = 11.747(2) Å, c = 10.748(2) Å, β = 125.59(3)°, V = 1837.7(6) ų, Z = 4, while the oxalate analogue 2 is seen to be in the trigonal space group P−31c with a = 8.8770(13) Å, b = 8.8770(13) Å, c = 10.482(2) Å, γ = 120°, V = 715.3(2) ų, Z = 2. The octahedral [Ni(en)₃] units in both 1 and 2 are seen to be strongly H-bonded to the dicarboxylate moieties through the coordinated en units leading to a three-dimensional network. However, in 1 the water molecules also take part in the H-bonding and contribute to the overall 3D structure. In both 1 and 2 the crystal packing is done with the [Ni(en)₃]²⁺ units with absolute configuration Λ(δδδ) and its mirror conformer with Δ configuration in exactly equal numbers. Spectral (IR and UV–Visible) and magnetic measurements were carried out and some of the ligand-field parameters like D_q, B and β were evaluated for all the four compounds. These values suggest the presence of octahedrally coordinated nickel(II) in all the four complexes. Spectral data suggest that 3 has the two chelating dap moieties and the fumarate coordinated in η¹ form through both its carboxylate moieties while 4 has one chelating dap and the oxalate moiety coordinated in η⁴-bis-chelating form. Though both 1 and 2 are made of the same type of [Ni(en)₃]²⁺ units their thermograms give entirely different thermal features; 1 showing three clearly successive and step-wise dissociation of each en unit while 2 having a combined loss of two en units in the first thermal step. The relevant thermodynamic and kinetic parameters like E_a and ΔS also could be evaluated for various thermal steps for the compounds 1–4 using Coats–Redfern equation.     

Vanadium(II) alkyls. Synthesis and X-ray crystal structures of trans-VMe2(dmpe)2 and cis-V(CH2SiMe3) 2(dmpe)2

Treatment of the vanadium(II) tetrahydroborate complex trans-V(η¹-BH₄)₂(dmpe)₂ with (trimethylsilyl) methyllithium gives the new vanadium(II) alkyl cis-V(CH₂SiMe₃)₂(dmpe)₂, where dmpe is the chelating diphosphine 1,2-bis(dimethylphosphino)ethane. Interestingly, this complex could not be prepared from the chloride starting material VCl₂(dmpe)₂. The CH₂SiMe₃ complex has a magnetic moment of 3.8 μ_B, and has been characterized by ¹H NMR and EPR spectroscopy. The cis geometry of the CH₂SiMe₃ complex is somewhat unexpected, but in fact the structure can be rationalized on steric grounds. The X-ray crystal structure of cis-V(CH₂SiMe₃)₂(dmpe)₂ is described along with that of the related vanadium(II) alkyl complex trans-VMe₂(dmpe)₂. Comparisons of the bond distances and angles for VMe₂(dmpe) ₂, V---C = 2.310(5) Å, V---P = 2.455(5) Å, and P---V---P = 83.5(2)° with those of V(CH₂SiMe₃)₂(dmpe)₂, V---C = 2.253(3) Å, V---P = 2.551(1) Å, and P ---V---P = 79.37(3)° show differences due to the differing trans influences of alkyl and phosphine ligands, and due to steric crowding in latter molecule. The V---P bond distances also suggest that metal-phosphorus π-back bonding is important in these early transition metal systems. Crystal data for VMe₂(dmpe)₂ at 25°C: space group P2₁/n, with a = 9.041(1) Å, b = 12.815(2) Å, c = 9.905(2) Å, β = 93.20(1)°, V = 1145.8(5) ų, Z = 2, R_F = 0.106, and R_wF =0.127 for 74 variables and 728 data for which I 2.58 σ(I); crystal data for V(CH₂SiMe₃)₂(dmpe)₂ at −75°C: space group C2/c, with a = 9.652(4) Å, b = 17.958(5) Å, c = 18.524(4) Å, β = 102.07(3)°, V= 3140(3) ų, Z = 4, R_F = 0.033, and R_wF = 0.032 for 231 variables and 1946 data for which I 2.58 σ(I).     

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.     

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.     

Reaction of hexanuclear niobium and tantalum halide clusters with mercury(II) halides. II. Semiconducting compounds with [Ta6Cl12] unit

A series of paramagnetic clusters of the composition [(Ta₆Cl₁₂)Cl(H₂O)₅][HgX₄] · 9H₂)O (X = Cl, Br, I) has been prepared by the reaction of [Ta₆Cl₁₂]³⁺ methanol-water solutions with HgX₂ and NaX halides. The structure of [(Ta₆Cl₁₂)Cl(H₂O)₅][HgBr₄] · 9H₂O has been solved by X-ray diffraction in the cubic space group Fd 3m. Crystal data: a = 20.036(2) Å, V = 8043.0(1) ų, Z = 8, R = 0.048 (R_w = 0.051). The structure is composed of an octahedral [(Ta₆Cl₁₂)Cl(H₂O)₅]²⁺ cluster cation, tetrahedral [HgBr₄]²⁻ anion and crystal water molecules. The 2mm symmetry of the octahedron is reduced by the statistical distribution of the five water molecules, O(1), and chlorine, Cl(2), at the terminal coordination sites. Thus, the distances Ta-O(1) and Ta-Cl(2) are averaged to the value of 2.32(2) Å. The Ta-Ta and Ta-Cl(1) bond distances are 2.911(1) Å and 2.440(3) Å, respectively, whereas the Hg-Br bond distance is 2.564(3) Å. The cluster [(Ta₆Cl₁₂)Cl(H₂O)₅][HgBr₄] · 9H₂O is semiconducting with two levels governing conductivity with respective activation energies, E_al = 0.24 eV and E_a2 = 0.17 eV.     

Carbomolybdate clusters formed by carbonyl insertion into molybdenum-oxygen bonds. Structural investigation of the [RMo4O15X] core (R = ---C9H4O, X = OCH3; R = ---C14H10, X = ---C7H5O2; R = C14H8, X = ---OH)

[C₄H₉)₄N]₂[Mo₂O₇] reacts with a variety of organic species containing α-diketone groups to give tetranuclear complexes of general composition [RMo₄O₁₅X]³⁻. The complexes [(C₄H₉)₄N]₃[(C₉H₄O)Mo₄O₁₅(OCH₃)] (I), [(C₄H₉)₄N]₃[(C₁₄H₁₀)Mo₄O₁₅(C₆H₅CO₂)] (11) and [(C₄H₉)₄N]₃[(C₁₄H₈)Mo₄O₁₅(OH)] (III) were synthesized from the reactions of dimolybdate with ninhydrin, benzil and phenanthraquinone, respectively. Complex II may also be prepared from dimolybdate and benzoin in acetonitrile-methanol solution, from which it co-crystallizes with the binuclear species [(C₄H₉)₄N]₂[Mo₂O₅(C₆H₅C(O)C(O)C₆H₅)₂] · CH₃CN · CH₃OH (IV). Complexes I–III exhibit the tetranuclear core, previously described for the α-glyoxal derivatives [(C₄H₉)₄N]₃[(HCCH)Mo₄O₁₅X], where X = F⁻ or HCO₂⁻. The ligands may be formally described as diketals, formed by insertion of ligand carbonyl subunits into molybdenum-oxygen bonds. The structures I–III differ most dramatically in the identity and coordination mode of the anionic ligand X⁻ which occupies a position opposite the diketal moiety relative to the [Mo₄O₁₁]²⁺ central cage. Thus, I exhibits a doubly bridging methoxy group in this position, while II possesses a benzoate ligand with an unusual μ₃-O,O′coordination mode. Complex III presents a hydroxy-group unsymmetrically bonded to three of the molybdenum centres. The stereochemical consequences of the various coordination modes are discussed. Crystal data: Compound I, monoclinic space group Pc, a = 24.888(2), b = 12.897(3), c = 24.900(3) Å, β = 101.94(2)°, D_calc = 1.28 g cm⁻¹ for Z = 4. Structure solution and refinement based on 8695 reflections with F_o 6σ(F_o) (Mo-K_α, λ = 0.71073 Å) converged at a conventional discrepancy factor of 0.060. Compound II, orthorhombic space group Pbca, a = 20.426(6), b = 26.916(6), c = 32.147(7) Å, V = 17673.2(20) ų, D_calc = 1.33 g cm⁻³ for Z = 8; 5224 reflections, R = 0.076. Compound III, tetragonal space group I4₁/a, a = b = 48.129(6), c = 13.057(2) Å, V = 30246.2(12) ų, D_calc = 1.35 g cm⁻³ for Z = 16; 5554 reflections, R = 0.053. Compound IV, orthorhombic space group Pnca, a = 16.097(4), b = 16.755(4), c = 25.986(7) Å, V = 7008.1(13) ų, Z = 4, D_calc = 1.18 g cm⁻³ ; 2944 reflections, R = 0.061.     

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%).     

A Molybdenum V Diphosphate Involving LiO4 Tetrahedra: LiMoOP2O7

A lithium Mo(V) diphosphate LiMoOP₂O₇ has been synthesized for the first time. It crystallizes in the space group P 2_1/n with a = 16.046(4) Å, b = 11.951(2) Å, c = 9.937(2) Å, β = 104.62(2)°. Its original structure is built up from P₂O₇ groups and MoO₆ octahedra forming intersecting tunnels, where the Li⁺ cations are located with a tetrahedral coordination. This phase belongs to the IB class of Mo(V) phosphates defined by Costentin et al. The [MoP₂O₈] framework indeed consists of MoP₂O₁₁ units built up from one P₂O₇ group sharing two apices with the same MoO₆ octahedron; the MoP₂O₁₁ units share their apices forming [MoP₂O₁₀]∞ chains running along a and b and the [ 04] direction. This phase exhibits a classical paramagnetic behavior, with 0 = -9.8 K and μ = 1.58 μ_B.     

X-Ray Diffraction Study of Cs5(HSO4)3(H2PO4)2, a New Solid Acid with a Unique Hydrogen-Bond Network

Solid solution investigations in the CsHSO₄–CsH₂PO₄system, carried out as part of an ongoing effort to elucidate the relationship between proton conduction, hydrogen bonding, and phase transitions, yielded the new compound Cs₅(HSO₄)₃(H₂PO₄)₂. Single-crystal X-ray diffraction methods revealed that Cs₅(HSO₄)₃(H₂PO₄)₂crystallizes in space groupC2/c(or possiblyCc), has lattice parametersa=34.066(19) Å,b=7.661(4) Å,c=9.158(6) Å, andβ=90.44(6)°, a unit cell volume of 2389.9(24) ų, a density of 3.198 Mg m⁻³, and four formula units in the unit cell. Sixteen non-hydrogen atoms and five hydrogen sites were located in the asymmetric unit, the latter on the basis of geometric considerations rather than from Fourier difference maps. Refinement using anisotropic temperature factors for all non-hydrogen atoms and fixed isotropic temperature factors for all hydrogen atoms yielded residuals based onF²(weighted) andFvalues, respectively, of 0.0767 and 0.0340 for observed reflections [F²>2σ(F²)]. The structure contains layers of (CsH₂XO₄)₂that alternate with layers of (CsHXO₄)₃, whereXis P or S. The arrangement of Cs, H, andXO₄groups within the two types of layers is almost identical to that in the end-member compounds, CsH₂PO₄and CsHSO₄-II, respectively. Although P and S each reside on two of the threeXatom sites in Cs₅(HSO₄)₃(H₂PO₄)₂, the number of protons in the structure appears fixed. In addition, the correlation of S–O and S–OH bond distances with O···O distances, where the latter represents the distance between two hydrogen-bonded oxygen atoms, was determined from a review of literature data.     

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 of Hg2FeF5(OH)2 · H2O

The new compound Hg₂FeF₅(OH)₂ · H₂O was prepared by evaporation of an aqueous 40% HF solution containing HgO and FeF₃ in the stoichiometric ratio. The material is orthorhombic, space group Cmmm, with a = 7.505(1) Å, b = 11.823(3) Å, c = 3.941(2)Å, and Z = 2. The crystal structure was determined from single crystal intensity data obtained by means of an automated four-circle diffractometer and refined to the conventional values R = 0.0621 and R_w = 0.0566 for 451 observed reflections. The structure is characterized by infinite straight chains of FeF₆ octahedra sharing trans F atoms in the direction [001]. These chains are linked by rutile-type chains of HgF₄(OH)₂ octahedra also running along [001]. Water molecules are statistically distributed on half of the 4i positions; they are off-centered in the channels parallel to [001] allowing O---H ··· F bonding. The structure is compared to that of HgFeF₅ · 2H₂O and to that of the hexagonal tungsten bronze.     

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.     

The Crystal Structures of the Strontium Gallates Sr10Ga6O19 and Sr3Ga2O6

The crystal structures of Sr₁₀Ga₆O₁₉ and Sr₃Ga₂O₆ have been characterized using X-ray diffraction techniques. In the case of Sr₁₀Ga₆O₁₉, the structure was determined from a single crystal diffraction data set collected at room conditions and refined to a final R index of 0.061 for 3471 observed reflections (I>2 σ(I)). The compound is monoclinic with space group C12/c1 (a=34.973(4) Å, b=7.934(1) Å, c=15.943(2) Å, β=103.55(1)°, V=4300.7(6) ų, Z=8, D_calc=4.94 g/cm³, μ(MoKα)=32.04 mm⁻¹) and can be classified as an oligogallate. It is the first example of an inorganic compound where six [TO₄]-tetrahedra of only one chemical species occupying the tetrahedral centres are linked via bridging oxygen atoms to form [T₆O₁₉] groups. The hexamers are not linear, but highly puckered. Eleven symmetrically different Sr cations located in planes parallel (100) crosslink between the oligo-groups. They are coordinated by six to eight oxygen ligands. The structure of Sr₃Ga₂O₆ has been refined from powder diffraction data using the Rietveld method (space group Pa , a=16.1049(1), V=4177.1(1) ų, Z=24, D_calc=4.75 g/cm³). The compound is isostructural with tricalcium aluminate and contains highly puckered, six-membered [Ga₆O₁₈]¹⁸⁻ rings. The rings are linked by strontium cations having six to nine nearest oxygen neighbors.     

[{(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.     

Structure and properties of triclinic Ni0.85Mo6Te8

The structure of Ni_0.85Mo₆Te₈ was refined from single-crystal X-ray diffraction data at room temperature. It is triclinic, space group

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; 1619 reflections, 75 refined parameters, R = 0.031. The Mo atoms form distorted octahedral clusters (2.69 Å ≤ d_intra[Mo---Mo] ≤ 2.81 Å; 3.58 Å < d_inter[Mo---Mo]). The Ni atoms are disordered (site occupancy: 0.423(7); d[Ni---Ni] = 2.586(6) Å), and interact strongly with one Mo₆ cluster (d[Ni---Mo] = 2.603(3) and 2.958(3) Å), and weakly with another (d[Ni---Mo] = 2.985(3) Å). The structure transforms at 1057(5) K into a rhombohedral modification (a_hex = 10.457(2) Å, c_hex = 11.866(3) Å at 1073 K). Measurements on powders suggest metallic conductivity (5.1 × 10⁻⁴ Ω-cm at 293 K) and weakly temperature-dependent paramagnetism (110 × 10⁻⁶ emu/g at 100 K).     

Preparation and Structure of Cerium Titanates Ce2TiO5, Ce2TiO7, and Ce4Ti9O24

Compounds Ce₂TiO₅, Ce₂Ti₂O₇, and Ce₄Ti₉O₂₄ were prepared by heating appropriate mixtures of solids containing Ce⁴⁺ and Ti³⁺ or Ti which were placed in a platinum-silica-ampoule combination at T = 1250°C (3d) under vacuum. The new compounds were characterized by powder patterns. We obtained Ce₂TiO₅ which is isotypic to La₂TiO₅ and crystallizes in the Y₂TiO₅-type (space group Pnma) with a = 10.877(6) Å, b = 3.893(1) Å, c = 11.389(8) Å, Z = 4. Ce₂Ti₂O₇ is isotypic to La₂Ti₂O₇ and crystallizes in the monoclinic Ca₂Nb₂O₇ type (space group P 2₁) with a = 7.776(6) Å, b = 5.515(4) Å, c = 12.999(6) Å, β = 98.36(5), Z = 4. The compound Ce₄Ti₉O₂₄ crystallizes orthorhombic with a = 14.082(4) Å, b = 35.419(8) Å, c = 14.516(4) Å, Z = 16. The new cerium titanate Ce₄Ti₉O₂₄ is isotypic to Nd₄Ti₉O₂₄ (space group Fddd (No. 70)) which represents a novel type of structure.