European Journal of Solid State and Inorganic Chemistry最新文献

The aerial oxidation of aqueous suspensions of ferrous hydroxide precipitated from ferrous oxalate and caustic soda can lead to an iron (II)-iron (III) hydroxy-oxalate of the pyroaurite group, a GR(C₂O₄^2-) Green Rust. As other GR compounds, it is unstable with respect to the action of oxygen and oxidises later on. Its chemical composition was determined to be [Fe^II₆ Fe^III₂(OH)₁₆]²⁺[C₂O₄^2- · nH₂O], with n more likely equal to 3 on the basis of structural considerations. The composition does not vary and the Fe (II) / Fe (III) ratio in the compound is measured by means of transmission Mössbauer spectroscopy at 78 K and 20 K in the range from 2.8 to 3.2 for various samples at various stages of the reaction. GR(C₂O₄^2-) is paramagnetic at both temperatures and is unambiguously distinguished from ferrous hydroxide, the initial reactant, and magnetite, the main final product, which are magnetically ordered at 20 K. The spectrum of the GR compound is composed of three quadrupole doublets, one due to the Fe(III) cations characterised by a small quadrupole splitting ΔE_Q of 0.40 mm s⁻¹, and two due to the Fe(II) cations, characterised by larger ΔE_Q values of about 2.55 and 2.85 mm s⁻¹. Finally, from the observed equilibrium conditions between ferrous hydroxide and GR(C₂O₄^2-), the standard free enthalpy of formation of GR(C₂O₄^2-) was computed to be : ΔG°_f[Fe^II₆ Fe^III₂ (OH)₁₆]²⁺[C₂O₄^2- · 3H₂O] = −5383 ± 3 kJ mol⁻¹.

β-SrRh₂O₄, a novel high temperature phase, is prepared as black powder by solid state reaction of SrCO₃ with Rh in air. The compound crystallises in the space group P63c, Z = 1, with a = 3.0626(2) Å and c = 11.3996(7) Å. The structure consists of Cd1₂-type layers of edge sharing RhO₆ octahedra with an AABB oxygen layer sequence. Strontium is found in partial occupation of both available interlayer sites, in trigonal prismatic coordination.

The complex, K_2.5Na₂NH₄[Mo₂O₂S₂(cit)₂]·5H₂O (1), was obtained by crystallization from a solution of (NH₄)₂MoS₄, potassium citrate (K₃cit) and hydroxyl sodium in methanol and water under an atmosphere of pure nitrogen at ambient temperature. The crystals are triclinic, space group P1¯, a = 7.376 (3)Å, b = 14.620 (2) Å, c = 14.661 (1) Å, α = 71.10 (1)°, β = 81.77 (1)°, γ = 78.27(2)°, R = 0.0584 for 2545 observed (I > 2σ (I)) reflections. Single crystal structure analysis reveals that citrate ligand coordinated to molybdenum atom through two carboxylato oxygens and one deprotonated hydroxyl oxygen together with two bridging sulfur atoms and a terminal oxygen atom completes distorted coordination octahedron around each molybdenum atom. Principal dimensions are Mo = O₁, 1.707 Å (av); Mo-S_b, 2.341 Å (av); Mo-O_(hydroxyl), 2.021 Å (av); Mo-O_{(α-carboxyl)}, 2.1290 Å (av) and Mo-O_{(β-carboxyl)}, 2.268(av) Å. IR spectrum is in agreement with the structure.

The structure of ZnLiNbO₄ crystals grown directly from the stoichiometric melt by the Laser Heated Pedestal Growth technique has been determined by X-ray diffraction. ZnLiNbO₄ crystallizes in the space group P4₁22 (n^o 91) with a=6.0818(9) Å c=8.3818(17) Å and Z=4. The crystal structure is that of an ordered type of a tetragonal spinel with Nb and Li ions in octahedral environment and Zn ions in tetrahedral position.

The average structure in the space group C2/m at 130 K of strontium pentacyanonitrosylferrate(H) tetrahydrate (strontium nitroprusside tetrahydrate, Sr[Fe(CN)₅NO].4H₂O, space group P2/m, monoclinic, Z=4, a=19.816(24), b=7.563(7), c=8.406(9) Å, β=99.02°, V=1244(24) ų) has been determined using neutron diffraction. A final R factor 0.061 was obtained using 665 observed structure factors.

When going from room temperature to 130 K the space group C2/m changes to P2/m. A rearrangement of hydrogen atoms is produced due to 14.3, 17.2, 5.9 and 26° rotations of the planes of W1, W2, W3 and W4 water molecules, respectively. As a consequence of this structural modification, the weakening of some hydrogen bonds related to the W4 molecule and the reinforcement of the hydrogen bonds of the W2 molecule along the [0 1 0] direction are observed.

It has been found experimentally that phase diagram for the system Bi₂O₃CaOSrOCuO in SrO-rich region at 850°C in the open air includes three elementary tetrahedra: CaOSrOSr₆Bi₂O₁₁Sr₂CuO₃, CaOSr₂CuO₃Sr₆Bi₂O₁₁Sr_3,5Ca_0,5Bi₂O₇ and Sr₃Bi₂O₆Sr₆Bi₂O₁₁Sr_3,5Ca_0,5Bi₂O₇ Sr₂CuO₃. In the considered interval of corresponding oxide concentrations quaternary oxides are not formed under the above conditions.

The new ternary mixed-valent copper selenide K₃Cu₈Se₆ has been prepared by the reaction of elemental copper with K₂Se₃ and additional selenium (molar ratio 1: 3: 1) at 623 K. The compound crystallizes in the monoclinic space group C2/m and is isotypic to K₃Cu₈S₆, RbCu₈S₆, Rb₃Cu₈Se₆ and Cs₃Cu₈Se₆. The structure consists of $\text{1}\text{∞}$[Cu₈Se₆] layers which are separated by the potassium cations. The copper atoms are either tetrahedrally distorted or trigonal planar coordinated by the selenium atoms. In the crystal structure the trigonal planar coordinated Cu atoms form double chains which are running parallel to the b-axis. These double chains are connected into layers via the distorted CuSe₄ tetrahedra which share edges and corners with the Se₃ triangles around Cu. In this part of the structure a very short Cu-Cu distances of only 2.497 (2) Å appears which is shorter than the Cu-Cu distance in elemental copper. Because the tetrahedrally coordinated copper ions exhibit unusual large anisotropic displacement parameters at room temperature, a low-temperature structure determination was performed. At low temperatures the anisotropic displacement coefficients are significantly smaller for all atoms, but even at 150 K some coefficients for the tetrahedrally coordinated Cu atoms are twice as large as for the trigonal planar coordinated Cu centers. However, the experiment shows that the nature of the disorder seems to be predominantly due to an enlarged mobility of the copper ions at room-temperature which is freezed on cooling. Our give no hints for the formation of a superstructure like in K₃Cu₈S₆.

The crystal structure determination of the title compounds showed that they are isomorphous, revealing the general formula [M(H₂O)₄(py)₂](sac)₂·4H₂O. Their structures are built up of [M(H₂O)₄(py)₂]²⁺ cations, saccharinato anions and non-coordinated water molecules. The metal atom lies on the inversion center and is octahedrally coordinated by four water oxygens and two pyridine nitrogen atoms. The crystal structure packing is achieved through the hydrogen bonds of O_w⋯O_w, O_w⋯O and O_w⋯N type. Coordinated water molecules are hydrogen bonded to non-coordinated ones at the same time participating in hydrogen bonding with carbonyl oxygen and nitrogen atom from the saccharinato anions. Non-coordinated water molecules participate in hydrogen bonding with the oxygen atoms belonging to the saccharinato CO and SO₂ groups. The hydrogen bond network between the oxygen atoms belonging to the SO₂ group of the saccharinato anions and one of the non-coordinated water molecules (OW3) constructs the centrosymmetric cavity in the structure.

The title compound (named Mu-4) is a new layered aluminophosphate with a unusual A1/P ratio for this kind of materials. Mu-4 was obtained from a quasi non-aqueous mixture involving mainly diethylformamide (DEF) as solvent, in addition to limited amounts of water. DEF is decomposed during the synthesis and the resulting protonated diethylamine is occluded in the as-synthesized material. The crystal structure was determined by single crystal X-ray diffraction. The symmetry is triclinic, a=8.632(4) Å, b=9.267(7) Å, c= 17.461(10) Å, α=86.66(5)°, β=82.20(4)° and γ=89.28(5)°, space group P-1. The structure consists of anionic double sheets essentially built from double 4-ring (D4R) units. The inorganic layers are in strong interaction with water and the protonated amine which is located in the interlayer spacing. Another type of diethylamine protrudes into the 8-membered rings (8-MR) present in the layers. The characterization of this new aluminophosphate by ¹³C, ²⁷Al and ³¹P solid state NMR spectroscopy is also reported.

Infrared spectra (IR, FIR, DRIFT, 90 and 295 K) and DSC measurements of the various polymorphs of iron oxide hydroxide, viz. goethite (α), akaganéite (β), lepidocrocite (γ), and feroxyhite (δ), and of deuterated specimens are reported. They are discussed with respect to the crystal structures proposed in the literature, the hydrogen bonds present, the energies of the OH stretching, OH bending (librational), and translational modes, and their thermal decomposition. From the two space groups proposed for β- and γ-FeO(OH), the groups I4/m and Cmc2₁, respectively, seem to be more reliable. The disorder of the OH⁻ ions of γ-FeO(OH) has not been confirmed in contrast to that of δ-FeO(OH). The intraionic O(H,D) distances of γ- and δ-FeO(OH) derived from neutron powder diffraction studies have to be doubted. The greater strength of the OHOH hydrogen bonds of lepidocrocite, for example, compared to that of the OHO hydrogen bonds of goethite despite the larger hydrogen bond acceptor capability of O²⁻ is due to the strong cooperativity of the hydrogen bonds of the γ-polymorph. The extremely different strength of the hydrogen bonds of isostructural α-AlO(OH) (v_OH = 2950 cm⁻¹, 295 K), α-MnO(OH) (v_OH = 2686 cm⁻¹), and α-FeO(OH) (v_OH = 3130 cm⁻¹) is caused by the different synergetic effect of the metal ions involved, especially that of Mn³⁺ due to its Jahn-Teller behaviour. The decomposition temperatures and heats of the various FeO(OH) modifications as well as the halfwidths of the DSC peaks evidence a much faster decomposition rate of akaganéite than those of the other polymorphs. This is obviously due to the Cl⁻ ion impurities present in this compound.