Li12Cu16+xAl26−x (x = 3.2): a new intermetallic structure type

The new ternary lithium copper aluminide, Li₁₂Cu_16+xAl_26−x (x = 3.2), dodecalithium nonadecacopper tricosaaluminide, crystallizes in a new structure type with space group P4/mbm. Among nine independent atomic positions, two Al (one of which is statistically disordered with Cu) and three Li atoms have point symmetry m.2m, two statistically disordered Al/Cu atoms are in m.. sites, one Al atom is in a 4/m.. site and one Cu atom occupies a general site. The framework of Li₁₂Cu_16+xAl_26−x consists of pseudo‐Frank–Kasper polyhedra enclosing channels of hexagonal prisms occupied by Li atoms. The crystallochemical peculiarity of this new structure type is discussed in relation to the derivatives from Laves phases (LiCuAl₂ and Li₈Cu_12+xAl_6−x) and to the well known CaCu₅ structure.     

Barium‐deficient celsian,Ba1−xAl2−2xSi2+2xO8 (x = 0.20 or 0.06)

Barium‐deficient forms of celsian (barium aluminium silicate) with the formula Ba_1−xAl_2−2xSi_2+2xO₈ (x = 0.20 and 0.06) have been identified. In contrast with the celsian–orthoclase solid solutions which have been reported previously, these forms, refined in the space group C2/m, with Ba and one O atom in the 4i sites with m site symmetry, and a further O atom in a 4g site with twofold axial symmetry, suggest a slight solid solution with silica. The serendipitous preparation of the compounds represents a possible hazard associated with solid‐state synthesis.     

Li12Cu12.60Al14.37: a new ternary derivative of the binary Laves phases

New ternary dodecalithium dodecacopper tetradecaaluminium, Li₁₂Cu_12.60Al_14.37 (trigonal, Rm, hR39), crystallizes as a new structure type and belongs to the structural family that derives from binary Laves phases. The Li atoms are enclosed in 15‐ and 16‐vertex and the Al3 atom in 14‐vertex pseudo‐Frank–Kasper polyhedra. The polyhedra around the statistical mixtures of (Cu,Al)1 and (Al,Cu)2 are distorted icosahedra. The electronic structure was calculated by the TB–LMTO–ASA (tight‐binding linear muffin‐tin orbital atomic spheres approximation) method. The electron localization function, which indicates bond formation, is mostly located at the Al atoms. Thus, Al—Al bonding is much stronger than Li—Al or Cu—Al bonding. This indicates that, besides metallic bonding which is dominant in this compound, weak covalent Al—Al interactions also exist.     

Substitutional disorder in Sr2−yEuyB2−2xSi2+3xAl2−xN8+x (x≃ 0.12, y≃ 0.10)

A novel nitride, Sr_2−yEu_yB_2−2xSi_2+3xAl_2−xN_8+x (x≃ 0.12, y≃ 0.10) (distrontium europium diboron disilicon dialuminium octanitride), with the space group P2c, was synthesized from Sr₃N₂, EuN, Si₃N₄, AlN and BN under nitrogen gas pressure. The structure consists of a host framework with Sr/Eu atoms accommodated in the cavities. The host framework is constructed by the linkage of MN₄ tetrahedra (M = Si, Al) and BN₃ triangles, and contains substitutional disorder described by the alternative occupation of B₂ or Si₂N on the (0, 0, z) axis. The B₂:Si₂N ratio contained in an entire crystal is about 9:1.     

Röntgenographische und schwingungsspektroskopische Untersuchung der Sulvanitmischkristalle Cu3Nb(SxSe1−x)4, Cu3Nb(SexTe1−x)4, und Cu3Ta(SxSe1−x)4 und Cu3Ta(SexTe1−x)4

X-Ray and Vibrational Studies of Sulvanite Mixed Cystals Cu₃Nb(S_xSe_1?x)₄, Cu₃Nb(Se_xTe_1?x)₄, Cu₃Ta(S_xSe_1?x)₄ and Cu₃Ta(Se_xTe_1?x)₄ Solid solutions Cu₃Nb(S_xSe_1?x)₄, Cu₃Nb(Se_xTe_1?x)₄, Cu₃Ta(S_xSe_1?x)₄ and Cu₃Ta(Se_xTe_1?x)₄ with sulvanite structure have been prepared in the range 0 ≤ x ≤ 1. The lattice constants in all systems obey the Vegard rule. Infrared and Raman spectra have been measured. The spectra of the compounds with mixed anion sublattices show additional peaks, compared to those of the end members, because besides the polyhedra MX₄ and MY₄ also groups MX₃Y, MX₂Y₂, and MXY₃ are present, and all groups are able to oscillate independently. By comparison of the peak intensities and the statistical frequency of the groups according to the composition, the additional valence vibrations could be attributed to the groups.     

[CrIII8MII6]12+ Coordination Cubes (MII=Cu, Co)

[Cr^III₈M^II₆]¹²⁺ (M^II=Cu, Co) coordination cubes were constructed from a simple [Cr^IIIL₃] metalloligand and a “naked” M^II salt. The flexibility in the design proffers the potential to tune the physical properties, as all the constituent parts of the cage can be changed without structural alteration. Computational techniques (known in theoretical nuclear physics as statistical spectroscopy) in tandem with EPR spectroscopy are used to interpret the magnetic behavior.     

The novel arsenate Na4Co7−xAl2/3x(AsO4)6 (x = 1.37): crystal structure,charge‐distribution and bond‐valence‐sum investigations

The title compound, tetrasodium cobalt aluminium hexaarsenate, Na₄Co_7−xAl_2/3x(AsO₄)₆ (x = 1.37), is isostructural with K₄Ni₇(AsO₄)₆; however, in its crystal structure, some of the Co²⁺ ions are substituted by Al³⁺ in a fully occupied octahedral site (site symmetry 2/m) and a partially occupied tetrahedral site (site symmetry 2). A third octahedral site is fully occupied by Co²⁺ ions only. One of the two independent tetrahedral As atoms and two of its attached O atoms reside on a mirror plane, as do two of the three independent Na⁺ cations, all of which are present at half‐occupancy. The proposed structural model based on a careful investigation of the crystal data is supported by charge‐distribution (CHARDI) analysis and bond‐valence‐sum (BVS) calculations. The correlation between the X‐ray refinement and the validation results is discussed.     

Preparation of MxTa6−xS (M = V,Cr; x ≃ 1) A new columnar structure with interpenetrating metal icosahedra

The products of the high temperature reaction of Ta₂S with equimolar amounts of V and Cr, respectively, have been characterized by X-ray spectrometry and diffraction. The structures of the metal-rich compounds M_xTa_6?xS (M = V, Cr; x ? 1) have been determined from with single crystal X-ray intensities. The isotypic phases crystallize in the monoclinic space group C2/c four formula units per unit cell. The structure is interpreted as consisting of interpenetrating distorted metal icosahedra arranged to columns which in turn are connected to form layers via additional Ta? Ta interactions. Metal-sulphur and weaker metal–metal Bonds provide the linkage of the layers. The coordination about S is square antiprismatic. The structural relationship and fundamental distinctions between M_xTa_6?xS and Ta₆S are pointed out. Thermodynamic quantities are used to elucidate the various reaction products and differences between Ta_6?xV_xS and Cr_xTa_6?xS with respect to the phase widths.     

Die Seltenerdmetallpolyselenide Gd8Se15, Tb8Se15−x,Dy8Se15−x,Ho8Se15−x,Er8Se15−x und Y8Se15−x (0 < x ≤ 0.3) – Zunehmende Fehlordnung in ausgedünnten,planaren Selenschichten

The Rare Earth Metal Polyselenides Gd₈Se₁₅, Tb₈Se_15?x, Dy₈Se_15?x, Ho₈Se_15?x, Er₈Se_15?x, and Y₈Se_15?x – Increasing Disorder in Defective Planar Selenium Layers Single crystals of the rare earth metal polyselenides Gd₈Se₁₅, Tb₈Se_15?x, Dy₈Se_15?x, Ho₈Se_15?x, Er₈Se_15?x, and Y₈Se_15?x (0 < x ≤ 0.3) have been prepared by chemical transport reactions (1120 K→ 970 K, 14 days, I₂ as carrier) starting from pre‐annealed powders of nominal compositions between LnSe₂ and LnSe_1.9. The isostructural title compounds adopt a 3 × 4 × 2 superstructure of the ZrSSi type and can be described in space group Amm2 with lattice parameters of a = 12.161(1) Å, b = 16.212(2) Å and c = 16.631(2) Å (Gd₈Se₁₅), a = 12.094(2) Å, b = 16.123(2) Å and c = 16.550(2) Å (Tb₈Se_15?x), a = 12.036(2) Å, b = 16.060(2) Å and c = 16.475(2) Å (Dy₈Se_15?x), a = 11.993(2) Å, b = 15.999(2) Å and c = 16.471(2) Å (Ho₈Se_15?x), a = 11.908(2) Å, b = 15.921(2) Å and c = 16.428(2) Å (Er₈Se_15?x), and a = 12.045(2) Å, b = 16.072(3) Å and c = 16.626(3) Å (Y₈Se_15?x), respectively. The structure consists of puckered [LnSe] double slabs and planar Se layers alternating along [001]. The planar Se layers contain a disordered arrangement of dimers, Se^2? and vacancies. All compounds are semiconducting and contain trivalent rare earth metals (Ln³⁺).     

Bromsulfenyl(trihalogen)phosphonium-Salze Cl3−nBrnPSBr+AsF6− (n = 0 – 3) und Cl3PSBr+SbF6− — Oxidative Bromierung von Thiophosphorylhalogeniden

Bromosulfenyl(trihalogeno)phosphonium Salts Cl_3?nBr_nPSBr⁺AsF₆^? (n = 0 – 3) and Cl₃PSBr⁺SbF₆^? — Oxidative Bromination of Thiophosphorylhalides The bromosulfenyl(trihalogeno)phosphonium salts Cl_3?nBr_nPSBr⁺AsF₆^? (n = 0 – 3) and Cl₃PSBr⁺SbF₆^? are prepared by oxidative bromination of the corresponding thiophosphorylhalides with Br₂/MF₅ (M = As, Sb) and characterized by vibrational and NMR spectroscopy.     

Structural links between zeolite-type and clathrate hydrate-type materials: Synthesis and crystal Structure of [N(CH3)4]6[AlxSi8−xO18−x(OH)2+x] · 44H2O (x = 3–4)

A novel tetramethylammonium aluminosilicate hydrate with the approximate composition [NMe₄]₆[Al_xSi_8?xO_18?x(OH)_2+x] · 44H₂O (x = 3–4) has been identified by powder X-ray diffraction as a component in a polyphasic solid mixture which crystallized at room temperature from an aqueous NMe₄OH? Al₂O₃? SiO₂ solution. Large crystals of the novel hydrate phase could be mechanically selected from that mixture. The crystal structure has been determined from 1 196 unique MoKα diffraction data measured at 180 K: Tetragonal crystal system, cell constants a = 16.181(4) and c = 17.450(4) Å, space group P4/mnc with Z = 2 formula units per unit cell, R = 0.072. The host-guest compound is of polyhedral clathrate type with a mixed three-dimensional, (mainly) four-connected network composed of oligomeric aluminosilicate anions [Al_xSi_8?xO_18?x(OH)_2+x]^6? and H₂O molecules linked via hydrogen bonds O? H …? O. The aluminosilicate anions possess a cube-shaped (double four-ring) structure. Orientationally disordered cationic guest species NMe₄⁺ are enclosed in the large [4⁶6⁸] and [4¹5¹⁰6⁷] polyhedral voids of the host framework; the small [4⁶] cages (i.e. the double four-ring anions) and [4³5⁶] cages are empty. The hydrate is a further member in a recently discovered series of clathrates with mixed tetrahedral networks, which provides a structure-chemical link between zeolite- and clathrate hydrate-type host-guest compounds.     

The reaction of XeF+MF6− (M = As,Sb) with sulfuranes; preparation of CF3(O)F2+SbF6− and (CF3)2SOXeF+SbF6−

CF₃S(O)F, (CF₃)₂SO, CF₃SF₃, (CF₃)₂SF₂, and SF₄ react in different manner with XeF⁺MF₆^? (M?As, Sb). An oxidative fluorination is observed by CF₃S(O)F forming the persulfonium salt CF₃S(O)F₂⁺SbF₆^?, whereas by (CF₃)₂SO a simple addition product containing xenon can be isolated in form of the sulfonium salt (CF₃)₂SOXeF⁺SbF₆^?. On the contrary, the Lewis-acidic character of the XeF⁺-cation predominates against (CF₃)_nSF_4?n (n = 0 ? 2) leading to the corresponding fluorosulfonium salts (CF₃)_nSF_3?n ⁺MF₆^? (M?As, Sb) and XeF₂.