Cluster self-organization of TR-containing silicate and germanate systems: Suprapolyhedral precursors and self-assembly of A2HMTO5 (A = Li, Na; M = Sc, Lu, Yb) crystal structures with MTO5 frameworks

The combinatorial topological analysis is carried out using the coordination sequences method (the TOPOS 4.0 program package) and the matrix self-assembly is modeled for silicates Li₂HTRSiO₅ (TR = Lu, Yb; space group $P\bar 1$ ) and germanate Na₂HScGeO₅ (space group P2₁ ab). These compounds, having identical formulas, have different MT frameworks built of M octahedra (TRO₆) and T tetrahedra (SiO₄, GeO₄). New types of crystal-forming binodal nets are discovered: 4 4 6 6 + 4 4 6 for lutetium silicate and 44444(4⁵) + Ge 444(4³) for scandium germanate; the atom-site ratio in the nets is M: T = 1: 1. A ring invariant suprapolyhedral precursor cluster composed of four polyhedra is identified, with two (A = Li, Na) atoms lying one above and one below the center of the cluster. A₂M₂T₂ precursor clusters control the evolution of high-level crystal-forming clusters by means of the matrix assembly mechanism. The evolution routes of the suprapolyhedral precursor clusters bifurcate at the stage where topologically dissimilar layers are formed of equivalent chains. The cluster coordination numbers (CCNs) in a layer for the precursor clusters are four for lutetium silicate and six for scandium germanate.     

Modeling of self-organization of silicate systems: Precursor nanoclusters and self-assembly of Na<Subscript>3</Subscript>MSi<Subscript>3</Subscript>O<Subscript>9</Subscript> (M = Y,Eu-Lu; oP256) crystal structures producing two interpenetrating diamond-type frameworks

In the M-T-O model system (M is a polyvalent metal with CN ≥ 4; T is Si), cyclic clusters have been deduced as graphs in the T/M range from one to three. The case is considered when monocyclic cluster M₂T₂ is modified by T-tetrahedra that form diortho groups T₂. The M sites of the cluster have either topologically different local MT structures (four types) or identical local MT structures (two types). The cluster types for T/M = 3 obtained by modeling were used in analysis of one of the most complicated types of silicate crystal structures Na₃MSi₃O₉ (M = Y; Eu-Lu; T/M = 3) with the Pearson index oP256 and 64 independent atoms. The TOPOS program package was used to carry out the complete 3D reconstruction of the self-assembly of the crystal structure: suprapolyhedral precursor nanocluster → primary chain → microlayer → microframework (supraprecursor) → ... three-dimensional framework. The calculation of the coordination sequences of site atoms in the 3D network of the MT framework MT₃O₉ revealed topological symmetry related to a three-dimensional separation of the framework into two interpenetrating frameworks. Each framework structure is generated by topologically equivalent cyclic precursor clusters Na₂M₂T₆ consisting of two YO₆ octahedra comprising three diortho groups Si₂O₇ and two Na atoms located above and below the ring center. The 3D graphs characterizing the connectivity of the centers of crystallographically equivalent clusters in the frameworks correspond to diamond-type networks.     

Complex amidoboranes M<Superscript>2</Superscript>[M<Superscript>1</Superscript>(NH<Subscript>2</Subscript>BH<Subscript>3</Subscript>)<Subscript>4</Subscript>] (M<Superscript>1</Superscript> = Al,Ga; M<Superscript>2</Superscript> = Li,Na, K,Rb, Cs)

Structural, spectral, and thermodynamic characteristics of complex amidoboranes M²[M¹(NH₂BH₃)₄] (M¹ = Al, Ga; M² = Li, Na, K, Rb, Cs) were calculated by the B3LYP/def2-SVPD quantum-chemical method. The procedure for the synthesis of these compounds by reactions of alkali metal amidoboranes with aluminum and gallium chlorides was suggested and experimentally tested. Reaction products were characterized by the NMR and IR spectroscopy and X-ray phase analysis.     

Synthesis and crystal structure of EnH<Superscript>2</Superscript>[IrCl<Superscript>6</Superscript>]

The preparation of EnH²[IrCl⁶] is described. Crystal data for C₂H₁₀Cl₆IrN₂ are: a = 6.8972(11) Å, b = 6.9435(16) Å, c = 7.3354(11) Å; α = 88.269(3)°, β = 65.495(2)°, γ = 60.305(2)°, V = 270.76(9) ų, space group P1, Z = 1, d_calc = 2.864 g/cm³. Crystal chemical analysis of the general motif of the structure was performed by the translation sublattice identification technique. It has been found that complex anions [IrCl₆]^2? follow the nodes of a rather regular rhombohedral subcell with the parameters a_c = 7.1 Å, α_c = 64°.     

Dissymmetrization of crystal structures of grossular-andradite garnets Ca<Subscript>3</Subscript>(Al,Fe)<Subscript>2</Subscript>(SiO<Subscript>4</Subscript>)<Subscript>3</Subscript>

The crystal structures of three birefringent grossular-andradite natural garnets Ca₃(Al,Fe)₂(SiO₄)₃ were investigated using single-crystal X-ray diffraction data (MoK_α, number of reflections measured 8065, 10619, 9213; R = 2.81, 2.74, 3.26%). According to the values of unit cell constants, inconsistent intensities of reflections and appearance of additional (forbidden) reflections explored garnets have different symmetry: cubic, sp. gr. (Fe/(Fe + Al) = 0.078, Δn = 0.0002); orthorhombic, sp. gr. Fddd (Fe/(Fe + Al) = 0.58, Δn = 0.0089); triclinic, sp. gr. or I1 and pseudo-orthorhombic (Fe/(Fe + Al) = 0.23, Δn = 0.0066). Careful refinement of all crystal structures in space groups , Fddd and has confirmed the symmetry reduction detected on the diffraction patterns and shown that dissymmetrization of cubic garnets connects with partial ordering of trivalent cations over Y-sites. Direct linear relationship between Fe-occupancy, an average Y–O bond lengths and octahedral O–O edges has been revealed. Cluster models of dissymmetrization have been regarded. Evidence for the “growth dissymmetrization” phenomena (kinetic phase transformations) as the reasons of the symmetry reduction of cubic garnets has been discussed. The reasonable assumption that the garnets crystal structures described as orthorhombic are triclinic, but the deviations from the orthorhombic symmetry so small, that cannot be manifested by of X-ray diffraction study has been taken.     

Synthesis,structures, IR spectra,and thermal characteristics of compounds of general formula Ba(M<Stack><Subscript>2/3</Subscript><Superscript>III</Superscript></Stack>U<Subscript>1/3</Subscript>)O<Subscript>3</Subscript> (M<Superscript>III</Superscript> = Sc,Y, In,Nd-Lu)

Compounds with the composition Ba(M _2/3 ^III U_1/3)O₃ (M^III = Sc, Y, In, Nd-Lu) were synthesized by high-temperature solid-state reactions. The structures of the compounds were studied by X-ray diffraction analysis, including the high-temperature method, and IR spectroscopy.     

Complexation of Zn<Subscript>2</Subscript>[Fe(CN)<Subscript>6</Subscript>] with M<Superscript>2+</Superscript> (M = Mn,Co, Ni,Cu, Cd) in Zn<Subscript>2</Subscript>[Fe(CN)<Subscript>6</Subscript>] gelatin-immobilized matrices

Electrophilic substitution reactions Zn²⁺ M²⁺ (M = Mn, Co, Ni, Cu, Cd) in thin gelatin layers with immobilized zinc(II) hexacyanoferrate brought in contact with the aqueous solutions of d-element chlorides are studied. In all cases (except for Mn(II)), Zn atoms are partially replaced by all metals in question with the formation of the corresponding binuclear ZnM hexacyanoferrates(II). No complete replacement of Zn(II) to mononuclear hexacyanoferrate(II) of substituting metal occurs in neither of the cases.Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 2, 2005, pp. 110–116. Original Russian Text Copyright © 2005 by Tatarintseva, Mikhailov, Naumkina, Lygina.     

Synthesis and crystal structure of [Co(NH<Subscript>3</Subscript>)<Subscript>6</Subscript>][AuX<Subscript>4</Subscript>]X<Subscript>2</Subscript> (X = Cl<Superscript>−</Superscript>, Br<Superscript>−</Superscript>)

[Co(NH₃)₆][AuX₄]X₂ binary complex salts, where X = Cl^? (I) and Br^? (II), have been obtained and defined by element, X-ray diffraction, and thermal analyses and by IR, Raman, and electron spectroscopy. The compounds are isostructural. Their structural units are the [Co(NH₃)₆]³⁺ complex cations, the [AuX₄]^? complex anions, and the X^? anions. The plane square environment of the gold atom is completed to an elongated bipyramid by two halide ions lying at distances Au...Cl 3.245 Å for I and Au...Br 3.362 Å for II. The thermolysis products of I and II are pure gold and cobalt metal powders when thermolysis is performed under hydrogen and a mixture of metallic gold with cobalt halide in a reaction under an inert atmosphere.     

Rare Earth-Rich Indides <Emphasis Type="Italic">RE</Emphasis><Subscript>5</Subscript>Pt<Subscript>2</Subscript>In<Subscript>4</Subscript> (<Emphasis Type="Italic">RE</Emphasis> = Sc,Y, La–Nd,Sm, Gd–Tm,Lu)

Summary. The isotypic indides RE ₅Pt₂In₄ (RE = Sc, Y, La–Nd, Sm, Gd–Tm, Lu) were synthesized by arc-melting of the elements and subsequent annealing. They were investigated via X-ray powder diffraction. Small single crystals of Gd₅Pt₂In₄ were grown via slow cooling and the structure was refined from X-ray single crystal diffractometer data: Pbam, a = 1819.2(9), b = 803.2(3), c = 367.6(2) pm, wR ² = 0.089, 893 F ² values and 36 parameters. The structure is an intergrowth variant of distorted trigonal and square prismatic slabs of compositions GdPt and GdIn. Together the platinum and indium atoms build up one-dimensional [Pt₂In₄] networks (292–333 pm Pt–In and 328–368 pm In–In) in an AA stacking sequence along the c axis. The gadolinium atoms fill distorted square and pentagonal prismatic cages between these networks with strong bonding to the platinum atoms.     

Cluster self-organization of Li-and TR-containing germanate systems: Suprapolyhedral precursors and self-assembly of LiScGeO4 and LiHo3(GeO4)2F2 crystal structures

The combinatorial and topologic analysis (the TOPOS 4.0 program package, the coordination sequences method) is carried out for the crystal structures of the orthogermanates Li^[6]Sc^[6]Ge^[4]O₄ (the olivine type, space group Pnuma) and Li^[6]Ho^[8]Ho ₂ ^[7] (GeO₄)₂F₂ (space group I2/c). The same type of 2D TR,Ge-net with the Schläfli index of 3⁴4² + 3²4² and the site ratio of TR: Ge = 1: 1 is discovered for both structures. Four-polyhedral ring precursor clusters (TR)₂T₂ are identified using the two-color decomposition of structural graphs. All the clusters have a symmetry center; they differ in the types of TR polyhedra (ScO₆ and HoO₆F), which are linked through GeO₄ orthotetrahedra into a ring. The Li atoms reside above and under the centers of the clusters. The Li₂(TR)₂T₂ clusters determine the formation of crystal-forming clusters of a higher level by means of matrix self-assembly. The coordination number of the precursor clusters in the 2D net is six, which is the highest possible value.     

Dielectric constant and dielectric relaxation in aqueous solutions of K<Subscript>2</Subscript>[PdCl<Subscript>4</Subscript>] and K<Subscript>2</Subscript>[PtCl<Subscript>4</Subscript>]

The MW-dielectric properties of aqueous solutions of K₂[PtCl₄] (I) and K₂[PdCl₄] (II) were studied at 298 and 313 K in the frequency range (12–25 GHz) corresponding to the maximum dielectric constant dispersion for water and aqueous solutions of these salts. The low-frequency conductivities were measured. The static dielectric constant, the dielectric relaxation time, and the enthalpy of activation of the dielectric relaxation of the solutions were determined. Compared to pure water, in solutions of salts I and II, the orientational mobility of water molecules is increased and the network of H-bonds is violated more strongly than that of most other ions with hydrophilic hydration. It was demonstrated for the first time that dielectric spectroscopy can be used for analyzing complexation processes in systems containing aqua and hydroxo chloride complexes of metals.     

Hydrothermal synthesis,characterization, and thermal properties of alumino silicate azide sodalite,Na<Subscript>8</Subscript>[AlSiO<Subscript>4</Subscript>]<Subscript>6</Subscript>(N<Subscript>3</Subscript>)<Subscript>2</Subscript>

First time we report the synthesis, structural characterization and thermal behavior of an unusual N₃ ^? containing alumino-silicate sodalite mineral. Azide sodalite, Na₈[AlSiO₄]₆(N₃)₂ has been synthesized under hydrothermal conditions at 433 K in steel lined Teflon autoclave. The structural and microstructural properties of azide sodalite mineral was characterized by various methods including FT-IR, XRD, SEM, TGA, and MAS NMR. Crystal structure have been refined by Rietveld method in \(P\bar 43n\) space group, indicating that the N₃ ^? sodalite has cubic in lattice. High temperature study was carried out to see the effect of thermal expansion on cell dimension (a ^o) of azide sodalite. Thermal behavior of sodalite was also assessed by thermogravimetric method.     

Structures and bonding of the complexes [M(η<Superscript>5</Superscript>-E<Subscript>5</Subscript>)] and [M(η<Superscript>5</Superscript>-E<Subscript>5</Subscript>)<Subscript>2</Subscript>] (M = Sc,Y, E = N,P): a DFT study

The mono- and bisligands complexes formed by rare earth cation (Sc, Y) with pentazolato anion or cyclo-P₅⁻ anion, the all-nitrogen counterparts of metallocenes or the all-phosphorus counterparts of metallocenes, have been studied at hybrid basis sets level with the DFT method. The geometric parameters, binding energy and the charge distributions of these complexes were characterized. And their stable orders were obtained. Monoligand complexes incline to become bisligands complexes due to their destabilization. The charge transferring between ligand and metallic cation has affinity with the stability of complex. The possibility of forming stable [M(η ⁵-E₅)₂] (M = Sc, Y, E = N, P) complexes is predicted and they are viable synthetic targets theoretically, especially Sc(η ⁵-N₅)₂.     

Synthesis,structure formation,and thermal expansion of A<Superscript>+</Superscript>M<Superscript>2+</Superscript>MgE<Superscript>4+</Superscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>

The compounds AMMgE(PO₄)₃ (A = Na, K, Rb, Cs; M = Sr, Pb, Ba; E = Ti, Zr) were synthesized by the sol–gel procedure followed by heat treatment and studied by X-ray diffraction, differential thermal and electron microprobe analysis, and IR spectroscopy. The phosphates crystallize in the kosnarite (KZr₂(PO₄)₃, space group \(R\bar 3\)) and langbeinite (K₂Mg₂(SO₄)₃, space group P2₁3) structural types. The structure of KPbMgTi(PO₄)₃ was refined by full-profile analysis (space group P2₁3, Z = 4, a = 9.8540(3) Å, V = 956.83(4) ų). The structure is formed by a framework of vertex-sharing MgO₆ and TiO₆ octahedra and PO₄ tetrahedra. The K and Pb atoms fully occupy the extra-framework cavities and are coordinated to nine oxygen atoms. A variable-temperature X-ray diffraction study of KPbMgTi(PO₄)₃ showed that the compound expands isotropically and refer to medium-expansion class (linear thermal expansion coefficients α _a = α _b = α _c = 8 × 10^–6°C^–1). The number of stretching and bending modes of the PO₄ tetrahedron observed in the IR spectra is in agreement with that predicted by the factor group analysis of vibrations for space groups \(R\bar 3\) and P2₁3. A structural transition from the cubic langbeinite to the rhombohedral kosnarite was found for CsSrMgZr(PO₄)₃. In the morphotropic series of ASrMgZr(PO₄)₃ (A = Na, K, Rb, Cs) the kosnarite–langbeinite transition occurs upon the Na → K replacement. The effect of the sizes and electronegativities of cations combined in AMMgE(PO₄)₃ on the change of the structural type was analyzed.     

X-ray diffraction study of [M<Superscript>I</Superscript>(NH<Subscript>3</Subscript>)<Subscript>5</Subscript>Cl] [M<Superscript>II</Superscript>Br<Subscript>6</Subscript>] (M<Superscript>I</Superscript> = Rh,Ir; M<Superscript>II</Superscript> = Re,Ir) polycrystals

Based on the X-ray diffraction data for polycrystals, the crystal structures of double complex salts [Rh(NH₃)₅Cl][ReBr₆] and [Ir(NH₃)₅Cl][ReBr₆] are refined. The structure of [Rh(NH₃)₅Cl][IrBr₆] is determined. Initial models are constructed using the Monte Carlo method in the straight space. Further refinement is made by the Rietveld method. It is shown that such an approach is suitable for the refinement of crystal structures composed of isolated rigid polyhedra and can be used to determine the structure of salts without structural analogues     

Facilitated Transport of C<Subscript>2</Subscript>H<Subscript>4</Subscript> in a SiO<Subscript>2</Subscript>-poly(N-vinylpyrrolidone)-Ag<Superscript>+</Superscript> Inorganic-Organic Hybrid Membrane

Inorganic-organic hybrid membranes containing silica as the structure matrix, poly(N-vinylpyrrolidone) (PVP) as the organic mediating agent and silver ions as olefinic carriers were prepared using sol–gel method and dip-coating process. The structure and permeances of the membranes for N₂, He, C₂H₄, C₂H₆ at different temperatures indicated that defect-free membranes were obtained and the transportation of the C₂H₄ through the membranes followed the dissolution and diffusion mechanism. Ideal separation factors of C₂H₄/C₂H₆ through the membranes were evaluated at the temperature of 298, 373 and 423 K respectively using mixture gas of 50% C₂H₄-50% C₂H₆. The results showed that the ideal separation factors of C₂H₄/C₂H₆ through the membranes were obviously greater than the ratio of PC₂H₄/PC₂H₆ obtained from the single gas measurement due to the hindering effect by the adsorbed C₂H₄. The ideal separation factors of C₂H₄/C₂H₆ increased with temperature and reached 10 at 423 K, which suggested that C₂H₄ and C₂H₆ could be separated at lower humidity compared to the reported organic polymer/silver salt membranes in which humidified gases and higher silver loading were usually used. The transport of C₂H₄ in the inorganic-organic hybrid membrane was proposed to follow the hopping mechanism, that is, olefins moved across the fixed silver sites.     

Synthesis and X-ray investigation of Rb<Subscript>2</Subscript>[Pd(NO<Subscript>3</Subscript>)<Subscript>4</Subscript>] and Cs<Subscript>2</Subscript>[Pd(NO<Subscript>3</Subscript>)<Subscript>4</Subscript>]

Powder and single crystal X-ray diffraction studies have been performed for anhydrous nitrate complexes Rb₂[Pd(NO₃)₄] (I) and Cs₂[Pd(NO₃)₄] (II). Crystal data for I: a = 7.843(1) Å, b = 7.970(1) Å, c = 9.725(1) Å; β = 100.39(1)°, V = 597.9(1) Å ³, space group P2₁/c, Z = 2, d _calc = 2.918 g/cm³; for II: a = 10.309(2) Å, b = 10.426(2) Å, c = 11.839(2) Å; β = 108.17(3)°, V = 1209.0(4) ų, space group P2₁/c, Z = 4, d ^calc = 3.408 g/cm³. The structures are formed by isolated [Pd(NO₃)₄]^2? complex anions and alkali metal cations. The plane-square environment of the Pd atom is formed from the oxygen atoms of the monodentate nitrate groups. The geometrical characteristics of the complex anions are analyzed. Compound II has a short contact Pd...Cs 3.252 Å.     

Crystal Structure of Tl<Subscript>2</Subscript>[NbCl<Subscript>6</Subscript>] and Tl<Subscript>2</Subscript>[NbBr<Subscript>6</Subscript>]

Single crystals of Tl₂[NbCl₆] (1) and Tl₂ [NbBr₆] (2) are obtained as black needles on heating TlCl, Nb, S₂Cl₂ (1) and Tl, Nb, and Br₂ at 400°C (2). Tl₂NbBr₆ also forms in the reaction of TlBr, Nb, Br₂, and S at 500°C. Both compounds crystallize in the K₂[PtCl₆] structure type to form non-distorted octahedral [NbХ₆]^2– anions (Nb–Cl 2.397(4) Å and Nb–Br 2.516(2) Å). The magnetic properties of Tl₂[NbBr₆] in a range 5-300 K indicate an antiferromagnetic interaction between Nb⁴⁺ ion spins (d¹, S = 1/2). On cooling, the compound becomes a noncollinear ferromagnet with T_c = 23 K.     

Kinetics of oxidation of methane to formaldehyde on Na<Subscript>4</Subscript>[PFeMo<Subscript>11</Subscript>O<Subscript>40</Subscript>]/SiO<Subscript>2</Subscript>

The kinetics of oxidation of CH₄ to formaldehyde on the catalytic system Na₄[PFeMo₁₁O₄₀]/SiO₂ were studied, and a significant role of the redox potential of the CH₄-O₂ system with respect to the catalyst was shown. The density of centers participating in the reaction was determined, and dissociative competitive adsorption of methane and oxygen was established. The equation was deduced in the framework of the Langmuir-Hinshelwood theory taking into account the side conversion of formaldehyde. Possible participation of lattice oxygen in the reaction was suggested.     

Manganites NdMg<Stack><Subscript>3</Subscript><Superscript>I</Superscript></Stack>Mg<Subscript>3</Subscript>Mn<Subscript>4</Subscript>O<Subscript>12</Subscript> (M<Superscript>I</Superscript> = Li,Na, K): X-ray diffraction data

NdLi₃Mg₃Mn₄O₁₂, NdNa₃Mg₃Mn₄O₁₂, and NdK₃Mg₃Mn₄O₁₂ manganites were synthesized for the first time by solid phase reactions of neodymium(III) and manganese(III) oxides with lithium, sodium, potassium, and magnesium carbonates. X-ray diffraction showed that the compounds crystallized in the tetragonal crystal system. Their unit cell parameters were determined.