Crystal chemistry peculiarities of Cs2Te4O12

The Raman and IR-absorption spectra of the Cs₂Te₄O₁₂ lattice are first recorded and interpreted. Extraordinary features observed in the structure and Raman spectra of Cs₂Te₄O₁₂ are analyzed by using ab initio and lattice-dynamical model calculations. This compound is specified as a caesium-tellurium tellurate Cs₂Te^IV(Te^VIO₄)₃ in which Te^IV atoms transfer their 5p electrons to [Te^VIO₄]₃⁶⁻ tellurate anions, thus fulfilling (jointly with Cs atoms) the role of cations. The Te^VI-O-Te^VI bridge vibration Raman intensity is found abnormally weak, which is reproduced by model treatment including the Cs⁺ ion polarizability properties in consideration.     

Die IR-Spektren der Phasen ABTe3O8 (A = Fe,In, Sc; B = Nb,Ta) und UTe3O9

I.R. Spectra of the Phases A B Te₃O₈ (A = Fe, In, Sc; B = Nb, Ta) and UTe₃O₉ The infrared spectra of the title compounds have been recorded and discussed in comparison to formerly investigated M^IVTe₃O₈ phases. The spectrum of UTe₃O₉ (synthetic cliffordite) confirms the presence of uranyl groups and the structural relation of this compound to the fluorite.     

The Crystal Structures and Raman Spectra of Three New Hydrothermally Synthesized Copper–Zinc–Oxotellurates(IV)

Abstract . Three new copper–zinc–tellurites, Zn₄Cu(Te^IVO₃)₄Cl₂, Cu₂Zn₂(Te^IVO₃)₂(SO₄)(OH)₂ · H₂O and Cu₂Zn(Te^IVO₄)(SO₄) · H₂O (henceforth I , II and III ), were synthesized under mild hydrothermal conditions (473 K, in Teflon-lined steel vessels). They were characterized in detail by a combination of crystal-structure determination (using single-crystal X-ray diffraction data), single-crystal micro-Raman spectroscopy and chemical analyses (energy-dispersive X-ray spectroscopy in a scanning electron microscope). Each compound crystallizes in a new structure type, and additionally, II and III represent the first two ever reported copper–zinc–tellurite–sulfates. I [systematic name: tetrazinc copper(II) tetrakis-oxotellurate(IV) dichloride] is triclinic, P1 , and forms a framework structure based on ZnO₆ and ZnO₅Cl octahedra, linked into sheets connected via Jahn–Teller-distorted CuO₄Cl₂ octahedra, with Te^IVO₃ trigonal pyramids and Te^IV₂O₆ dimers (composed of two edge-sharing Te^IVO₄ disphenoids) filling the remaining space. II [dicopper(II) dizinc bis-oxotellurate(IV) oxosulfate(VI) bis-hydroxide monohydrate] is trigonal, R3m, with a simonkolleite-like framework. Distinct layers formed from (Cu,Zn)φ₆ (φ = O, OH) octahedra and Te^IVO₃ trigonal pyramids extend parallel to (001) and sandwich disordered SO₄^2– anions and H₂O groups. III [dicopper(II) zinc oxotellurate(IV) oxosulfate(VI) hydrate] is orthorhombic, Pnma, and also has a layered structure [extending parallel to (100)]. Positively charged layers of composition [Cu₂ZnTe^IVO₄]²⁺ (containing Te as Te^IVO₄ disphenoids) alternate with SO₄^2– anions and H₂O groups in the interlayer space. Stacking disorder caused by the order-disorder nature of the crystal structure is reflected by the presence of residual electron density in difference-Fourier maps and the structure was refined as an overlay of two stacking possibilities.     

Incorporation of Sulfate or Selenate Groups into Oxotellurates(IV): I. Calcium,Cadmium, and Strontium Compounds

Seven new mixed oxochalcogenate compounds in the systems M^II/X^VI/Te^IV/O/(H), (M^II = Ca, Cd, Sr; X^VI = S, Se) were obtained under hydrothermal conditions (210 °C, one week). Crystal structure determinations based on single‐crystal X‐ray diffraction data revealed the compositions Ca₃(SeO₄)(TeO₃)₂, Ca₃(SeO₄)(Te₃O₈), Cd₃(SeO₄)(Te₃O₈), Cd₃(H₂O)(SO₄)(Te₃O₈), Cd₄(SO₄)(TeO₃)₃, Cd₅(SO₄)₂(TeO₃)₂(OH)₂, and Sr₃(H₂O)₂(SeO₄)(TeO₃)₂ for these phases. Peculiar features of the crystal structures of Ca₃(SeO₄)(TeO₃)₂, Ca₃(SeO₄)(Te₃O₈), Cd₃(SeO₄)(Te₃O₈), Cd₃(H₂O)(SO₄)(Te₃O₈), and Sr₃(H₂O)₂(SeO₄)(TeO₃)₂ are metal‐oxotellurate(IV) layers connected by bridging XO₄ tetrahedra and/or by hydrogen‐bonding interactions involving hydroxyl or water groups, whereas Cd₄(SO₄)(TeO₃)₃ and Cd₅(SO₄)₂(TeO₃)₂(OH)₂ crystallize as framework structures. Common to all crystal structures is the stereoactivity of the Te^IV electron lone pair for each oxotellurate(IV) unit, pointing either into the inter‐layer space, or into channels and cavities in the crystal structures.     

A non‐twinned polymorph of CaTe2O5 from a hydrothermally grown crystal

In contrast with the multiple twinning and/or domain formation found in the mica‐like polymorphs of CaTe₂O₅, calcium pentaoxidoditellurate(IV), that have been prepared by solid‐state reactions and for which complete structure determinations have not been successful up to now, the crystal structure of a hydrothermally grown phase was fully determined from a non‐twinned crystal. The structure is made up of alternating layers of Ca²⁺ cations and of ²_∞[Te₂O₅]²⁻ anions stacked along [100]. The lone‐pair electrons E of the Te^IV atoms are stereochemically active and protrude into channels within the anionic layer. In comparison with analogous M^IITe₂O₅ structures (M = Mg, Mn, Ni or Cu) with ditellurate(IV) anions that are exclusively made up of corner‐sharing TeO_x (x = 3–5) polyhedra resulting in flat ²_∞[Te₂O₅]²⁻ layers, the anionic layers in CaTe₂O₅ are undulating and are built of corner‐ and edge‐sharing [TeO₄] polyhedra.     

Tellurite des zweiwertigen Mangans,Kobalts und Nickels

By solid state reactions of TeO₂ with MnO, CoO, and NiO under nitrogen, the following compounds were obtained and characterized by X-ray powder data: MTe₆O₁₃ (M = Mn, Co), MTe₂O₅ and M₂Te₃O₈ (M = Mn, Ni), MnTeO₃, and M₄Te₃O₁₀, (M = Mn, Co) Mn₂Te₃O₈ and Ni₂Te₃O₈ crystallize with the monoclinic Zn₂Te₃O₈ structure. In respect of their structure, the compounds MTe₆O₁₃ and M₄Te₃O₁₀ are closely related to, or isostructural with, the corresponding magnesium compounds. Under the conditions of its formation. Mn₄Te₃O₁₀ slowly disproportionates to tellurium, Mn₃TeO₆ and MnTeO₃. A relation between the lattice energies of oxides MO and their reactions with TeO₂ is discussed.     

K2[Te4O8(OH)10]: synthesis,crystal structure and thermal behavior

Dipotassium octaoxodecahydroxotetratellurate, K₂[Te₄O₈(OH)₁₀], has been prepared hydrothermally in acidic medium under autogenous pressure. It crystallizes in space group P2₁/c of the monoclinic system with Z=2 in a cell of dimensions a=5.592(1) Å, b=8.283(2) Å, c=16.255(3) Å, and β=99.62(3)°. The outstanding feature of the structure is a tetrameric [Te₄O₈(OH)₁₀]^2– anion built up from edge and corner sharing TeO₆ octahedra. These anions and K⁺ cations are held together by electrostatic interactions and by hydrogen bonds. The compound decomposes in two steps at 350 and 420 °C, corresponding to a water and an oxygen loss, respectively, and affording the mixed valence oxide K₂Te^VI₃Te^IVO₁₂.     

New oxyfluorotellurates(IV): MTeO3F (M = FeIII,GaIII and CrIII)

The crystal structures of the new isomorphous compounds iron(III) oxyfluorotellurate(IV), FeTeO₃F, gallium(III) oxyfluorotellurate(IV), GaTeO₃F, and chromium(III) oxyfluorotellurate(IV), CrTeO₃F, consist of zigzag chains of MO₄F₂ distorted octahedra alternately sharing O–O and F–F edges and connected via TeO₃ trigonal pyramids. A full O/F anionic ordering is observed and the electronic lone pair of the Te^IV cation is stereochemically active.     

Methoxokomplexe drei-, vier- und fünfwertiger Zentralatome

The complex formation with CH₃O^? of As^III, Sb^III, Ge^IV, Nb^IV, Se^IV, Te^IV, Ti^IV, Sn^IV and Mo^V has been investigated in absolute methanolic solutions containing (CH₃)₄NCl, LiCl, or Lithiumtosylate (μ = 1; 20.0°) by means of pH-titrations. The relations between the stoichiometry of the reactions and the shape of the buffer regions, as well as the concentration-dependance of these buffer regions are discussed.     

Vibrational spectra of tellurates with the garnet structure

The IR and Raman spectra of tellurates Ln₃Te₂Li₃O₁₂ (Ln=Pr…Lu, Y), Ca₃Te₂Zn₃O₁₂ and Na₃Te₂M³⁺₃O₁₂ (M³⁺ = Al, Ga, Fe) with the garnet structure are presented and discussed on the basis of a group theoretical analysis, and of ⁶Li—⁷Li isotopic frequency shifts. The assignment of the high-frequency bands to stretching vibrations of the TeO₆ octahedra is only an approximation whose validity depends on the nature of the tetrahedral cation (Li, Zn or M³⁺) and of the symmetry properties of the vibrations: cationic mass effects play an important role in the antisymmetric, IR-active vibrations, whereas the bonding forces are the determining factor in the totally symmetric, Raman active vibrations. For the Na₃Te₂M³⁺₃O₁₂ garnets, the (TeO₆) internal modes approximation is unacceptable since the stretching frequencies of the TeO₆ and M³⁺O₄ groups are of the same order of magnitude. No detailed assignments are available for the medium-frequency bands: they are due in part to the bending vibrations of the TeO₆ octahedra, but the contribution of the tetrahedral cation Zn²⁺ or M³⁺ to this region of the spectrum remains largely unknown. The translational frequencies of the dodecahedral Ln³⁺ cations have been identified in the low frequency region (below 250 cm⁻¹) by comparison of the frequencies of the Ln and Y garnets.     

New vanadium(IV) and titanium(IV) oxyfluorotellurates(IV): V2Te2O7F2 and TiTeO3F2

As part of a continuing study of oxyfluorotellurates(IV), materials likely to present interesting nonlinear optical properties, two new phases, titanium(IV) tellurium(IV) trioxide difluoride, TiTeO₃F₂, and divanadium(IV) ditellurium(IV) heptaoxide difluoride, V₂Te₂O₇F₂, have been characterized and present, respectively, titanium and vanadium in the tetravalent state. The TiTeO₃F₂ structure is based on linear double rows of TiO₃F₃ polyhedra sharing vertices. These rows are connected to adjacent rows via two vertices of Te₂O₅ bipolyhedra. The Te, Ti, one F and two O atoms are on general positions, with one O and F statistically occupying the same site with half‐occupancy for each anion. One O and one F occupy sites with .m. symmetry. The V₂Te₂O₇F₂ structure consists of zigzag chains of VO₄F₂ octahedra alternately sharing O—O and F—F edges. These chains are connected via Te₂O₅ bipolyhedra, forming independent mixed layers. The Te, V, one F and three O atoms are on general positions while one O atom occupies a site of symmetry. In both phases, the electronic lone pair E of the Te^IV atom is stereochemically active. A full O/F anionic ordering is observed in V₂Te₂O₇F₂, but in TiTeO₃F₂ one of the six anionic sites is occupied by half oxygen and half fluorine, all the others being strictly ordered. These compounds represent new members of a growing family of oxyfluorotellurates(IV), including the recently characterized members of formula MTeO₃F, M being a trivalent cation. As was true for the previous members, they are characterized by an unusually high thermal and chemical stability in relation to the absence of direct Te—F bonds.     

Polarographie radiochimique des solutions acides de TeIV

With ¹²¹Te (T_1/2=17 days) radiochemical polarography of [Te^IV]≤10^?9M is possible with negligible surface coverage. Deposition of Te is diffusion controlled. The potential range of Te⁰ formation is limited at negative potential by its reduction to HTe^?.     

Darstellung und Eigenschaften einer neuen Reihe tellurhaltiger Perovskite des Typs K3MIIITe3O12

Preparation and Properties of a New Series of Tellurium Containing Perovskites of the Type K₃M^IIITe₃O₁₂ A new series of tellurium containing mixed oxides of composition K₃M^IIITe₃O₁₂ (M = Al, Ga, Cr, Fe) has been described. They crystallize in a superstructure-lattice of the PbTiO₃ type. The crystallographic data of the tetragonal unit cells have been determined from powder diffractograms. The i.r. spectra of these phases as well as the ⁵⁷Fe-Mössbauer-spectrum of K₃FeTe₃O₁₂ were recorded and discussed.     

Synthesis and Structural Characterization of New Phases in the Cubic M3Te2O6X2 (M = Sr,Ba; X = Cl,Br) Structure Family

Four alkaline earth oxotellurate(IV) halides with common formula M₃Te₂O₆X₂ (M = Sr, Ba; X = Cl, Br) have been prepared as polycrystalline powders and/or in the form of single crystals. All compounds crystallize in the cubic space group Fd$\bar{3}$ m with cell parameters a = 15.9351(4) Å for Sr₃Te₂O₆Cl₂ (single‐crystal X‐ray data), 16.052(5) Å for Sr₃Te₂O₆Br₂ (powder X‐ray data), 16.688(2) Å for Ba₃Te₂O₆Cl₂ (single‐crystal X‐ray data) and 16.8072(3) Å for Ba₃Te₂O₆Br_1.64Cl_0.36 (single‐crystal X‐ray data). The results of the crystal structure analyses reveal a rigid ${3}\atop{{\infty}}$ [M₃Te₂O₆]²⁺ framework which can be described as being composed of regular octahedra of two types of chemically non‐bonded M₆ octahedra that are capped by trigonal pyramidal [TeO₃] anions located above every second face of one of the M₆ octahedra. The halide X^– anions are situated in the voids of the ${3}\atop{{\infty}}$ [M₃Te₂O₆]²⁺ framework. Dependent on the nature of the halogen, the anions show various kinds of occupational disorder which eventually led to a revision of the previous structure model of Ba₃Te₂O₆Cl₂. A comparative discussion with other structures of general formula M₃Ch₂O₆X₂ (M = divalent metal; Ch = Te, Se; X = Cl, Br) is presented.     

Discovery of Heteroatom‐“Embedded” Te⊂{W18O54} Nanofunctional Polyoxometalates by Use of Cryospray Mass Spectrometry

The cryo game : Heteroatom‐embedded nanofunctional clusters are described that incorporate a [Te^VIO₆]^6? species contained within a {W₁₈O₅₄} cage. Not only does the tellurium‐based species activate the {W₁₈O₅₄} cluster surface for assembly of larger nanoscale structures, such as [H₁₀Te^VI₂W₅₈O₁₉₈]^26?, it also undergoes a redox transformation inside the cluster from [Te^VIO₆]^6? to [Te^IVO₃]^2?.

     

Synthesis, crystal structures and luminescence properties of the Eu-doped yttrium oxotellurates(IV) Y2Te4O11 and Y2Te5O13

Y₂Te₄O₁₁:Eu³⁺ and Y₂Te₅O₁₃:Eu³⁺ single crystals in sub-millimeter scale were synthesized from the binary oxides (Y₂O₃, Eu₂O₃ and TeO₂) using CsCl as fluxing agent. Crystallographic structures of the undoped yttrium oxotellurates(IV) Y₂Te₄O₁₁ and Y₂Te₅O₁₃ have been determined and refined from single-crystal X-ray diffraction data. In Y₂Te₄O₁₁, a layered structure is present where the reticulated sheets consisting of edge-sharing [YO₈]¹³⁻ polyhedra are interconnected by the oxotellurate(IV) units, whereas in Y₂Te₅O₁₃ only double chains of condensed yttrium-oxygen polyhedra with coordination numbers of 7 and 8 are left, now linked in two crystallographic directions by the oxotellurate(IV) entities. The Eu³⁺ luminescence spectra and the decay time from different energy levels of the doped compounds were investigated and all detected emission levels were identified. Luminescence properties of the Eu³⁺ cations have been interpreted in consideration of the now accessible detailed crystallographic data of the yttrium compounds, providing the possibility to examine the influence of the local symmetry of the oxygen coordination spheres.     

Acetonyl­di­chloro­[(Z)‐2‐chloro‐2‐phenyl­vinyl]­tellurium(IV), helical chains of metal complexes

The primary geometry about the Te^IV atom in the title compound, [TeCl₂(C₈H₆Cl)(C₃H₅O)] or C₁₁H₁₁Cl₃OTe, is a pseudo‐trigonal‐bipyramidal arrangement, with two Cl atoms in apical positions, and the lone pair of electrons and C atoms in the equatorial plane. The Te^IV atom is involved in three secondary interactions, two intramolecular [Te?O = 2.842 (3) Å and Te?Cl3 = 3.209 (1) Å] and one intermolecular [Te?Cl = 3.637 (1) Å], the latter giving rise to a helical chain. These helices are linked by C—H?O interchain interactions.     

Synthesis,X-ray diffraction and vibrational study of silicates and germanates isostructural with kentrolite Pb2Mn2Si2O9

New germanates Pb₂M^III₂Ge₂O₉ (M^III = Fe, Mn, Sc, In) and silicates Pb₂M^IIM^IVSi₂O₉ (M^II = Mg, Ni, Co, Cu for M^IV = Sn; M^II = Co, Ni for M^IV = Ti) have been synthesized by solid state reaction. Their X-ray powder diagrams may be indexed in the orthorhombic system and show that these compounds are isostructural with kentrolite Pb₂Mn₂Si₂O₉. Doubts are expressed about the published structure of kentrolite and it is shown that some aspects of the structure should be re-examined.The I.R. and Raman spectra of these compounds are fairly complicated, and their discussion is restricted to the region of SiO or GeO stretching frequencies. These spectra show the existence of a pyro-silicate or -germanate group. The symmetric and antisymmetric frequencies of the SiOSi bridge have been identified with the help of ²⁸Si³⁰Si isotopic shifts. Their difference ν_as?ν_sym depends on the ionic radius of the cations, and points to a non-linear bridge of the pyrosilicate group.     

Nickel vanadium tellurium oxide,NiV2Te2O10

Single crystals of nickel(II) divanadium(V) ditellurium(IV) decaoxide, NiV₂Te₂O₁₀, were synthesized via a transport reaction in sealed evacuated silica tubes. The compound crystallizes in the triclinic system (space group P). The Ni atoms are positioned in the 1c position on the inversion centre, while the V and Te atoms are in general positions 2i. The crystal structure is layered, the building units within a (010) layer being distorted VO₆ octahedra and NiO₆ octahedra. The metal–oxide layers are connected by distorted TeO₄E square pyramids (E being the 5s² lone electron pair of Te^IV) to form the framework. The structure contains corner‐sharing NiO₆ octahedra, corner‐ and edge‐sharing TeO₄E square pyramids, and corner‐ and edge‐sharing VO₆ octahedra. NiV₂Te₂O₁₀ is the first oxide containing all of the cations Ni^II, V^V and Te^IV.     

Crystal structures of lazulite-type oxidephosphates TiTi3O3(PO4)3 and M4Ti27O24(PO4)24 (M=Ti, Cr, Fe)

Single crystals of the oxidephosphates Ti^IIITi^IV₃O₃(PO₄)₃ (black), Cr^III₄Ti^IV₂₇O₂₄(PO₄)₂₄ (red-brown, transparent), and Fe^III₄Ti^IV₂₇O₂₄(PO₄)₂₄ (brown) with edge-lengths up to 0.3 mm were grown by chemical vapour transport. The crystal structures of these orthorhombic members (space group F2dd ) of the lazulite/lipscombite structure family were refined from single-crystal data [Ti^IIITi^IV₃O₃(PO₄)₃: Z=24, a=7.3261(9) Å, b=22.166(5) Å, c=39.239(8) Å, R₁=0.029, wR₂=0.084, 6055 independent reflections, 301 variables; Cr^III₄Ti^IV₂₇O₂₄(PO₄)₂₄: Z=1, a=7.419(3) Å, b=21.640(5) Å, c=13.057(4) Å, R₁=0.037, wR₂=0.097, 1524 independent reflections, 111 variables; Fe^III₄Ti^IV₂₇O₂₄(PO₄)₂₄: Z=1, a=7.4001(9) Å, b=21.7503(2) Å, c=12.775(3) Å, R₁=0.049, wR₂=0.140, 1240 independent reflections, 112 variables). For Ti^IIITi^IVO₃(PO₄)₃ a well-ordered structure built from dimers [Ti^III,IV₂O₉] and [Ti^IV,IV₂O₉] and phosphate tetrahedra is found. The metal sites in the crystal structures of Cr₄Ti₂₇O₂₄(PO₄)₂₄ and Fe₄Ti₂₇O₂₄(PO₄)₂₄, consisting of dimers [M^IIITi^IVO₉] and [Ti^IV,IV₂O₉], monomeric [Ti^IVO₆] octahedra, and phosphate tetrahedra, are heavily disordered. Site disorder, leading to partial occupancy of all octahedral voids of the parent lipscombite/lazulite structure, as well as splitting of the metal positions is observed. According to Guinier photographs Ti^III₄Ti^IV₂₇O₂₄(PO₄)₂₄ (a=7.418(2) Å, b=21.933(6) Å, c=12.948(7) Å) is isotypic to the oxidephosphates M^III₄Ti^IV₂₇O₂₄(PO₄)₂₄ (M^III: Cr, Fe). The UV/vis spectrum of Cr₄Ti₂₇O₂₄(PO₄)₂₄ reveals a rather small ligand-field splitting Δ_o=14,370 cm⁻¹ and a very low nephelauxetic ratio β=0.72 for the chromophores [Cr^IIIO₆] within the dimers [Cr^IIITi^IVO₉].