The Electrochemical Synthesis of Polycationic Clusters

As a new method for the synthesis of chalcogen polycationic clusters, the electrochemical dissolution of elemental tellurium in ionic liquids (IL) or in liquid SO₂ is presented. ILs used are ethylmethylimidazolium triflate [OTf]^? and tetraalkylammonium triflylimide [NTf₂]^?. Tristriflylmethanide [CTf₃]^? was used as [BuMeIm][CTf₃] as the electrolyte in SO₂. This allowed for the isolation of [Te₄][CTf₃]_2, [Te₆][OTf]₄, and [Te₈][NTf₂]₂ containing the square [Te₄]²⁺, the prismatic [Te₆]⁴⁺, and the novel barrelane‐shaped [Te₈]²⁺. The compounds are novel compositions as they do not contain the usual halometalate anions, but rather common weakly coordinating anions. The ¹²⁵Te NMR spectrum of an IL solution containing [Te₈]²⁺ features only one broad signal at 2700 ppm. DFT calculations show that slight concerted displacements within the [Te₈]²⁺ cluster lead to a fluxional molecular structure and a fast valence isomerism with a very low activation barrier of about 8 kJ mol^?1.     

Peroxide Coordination of Tellurium in Aqueous Solutions

Tellurium–peroxo complexes in aqueous solutions have never been reported. In this work, ammonium peroxotellurates (NH₄)₄Te₂(μ‐OO)₂(μ‐O)O₄(OH)₂ ( 1 ) and (NH₄)₅Te₂(μ‐OO)₂(μ‐O)O₅(OH)?1.28 H₂O?0.72 H₂O₂ ( 2 ) were isolated from 5 % hydrogen peroxide aqueous solutions of ammonium tellurate and characterized by single‐crystal and powder X‐ray diffraction analysis, by Raman spectroscopy and thermal analysis. The crystal structure of 1 comprises ammonium cations and a symmetric binuclear peroxotellurate anion [Te₂(μ‐OO)₂(μ‐O)O₄(OH)₂]^4?. The structure of 2 consists of an unsymmetrical [Te₂(μ‐OO)₂(μ‐O)O₅(OH)]^5? anion, ammonium cations, hydrogen peroxide, and water. Peroxotellurate anions in both 1 and 2 contain a binuclear Te₂(μ‐OO)₂(μ‐O) fragment with one μ‐oxo‐ and two μ‐peroxo bridging groups. ¹²⁵Te NMR spectroscopic analysis shows that the peroxo bridged bitellurate anions are the dominant species in solution, with 3–40 %wt H₂O₂ and for pH values above 9. DFT calculations of the peroxotellurate anion confirm its higher thermodynamic stability compared with those of the oxotellurate analogues. This is the first direct evidence for tellurium–peroxide coordination in any aqueous system and the first report of inorganic tellurium–peroxo complexes. General features common to all reported p‐block element peroxides could be discerned by the characterization of aqueous and crystalline peroxotellurates.     

[Te8]2[Ta4O4Cl16]: A Two‐dimensional Tellurium Polycation obtained via Ionic Liquid‐Based Synthesis

By reaction of elemental tellurium, tellurium(IV) chloride, tantalum(V) chloride and tantalum(V) oxychloride in the ionic liquid [BMIM]Cl ([BMIM]Cl:1‐Butyl‐3‐methylimidazolium chloride),[Te₈]₂[Ta₄O₄Cl₁₆] is obtained in the form of lucent black crystals. The title compound consists of infinite [Te–Te–(Te₆)]_n²⁺ chains (Te–Te: 264.9(1)–284.3(1) pm) and isolated [Ta₄O₄Cl₁₆]^4– anions. The [Te–Te–(Te₆)]_n²⁺ chains are interconnected to form a two‐dimensional tellurium network (Te–Te: 335.9 pm). Due to this interaction the [Te–Te–(Te₆)]_n²⁺ chains in [Te₈]₂[Ta₄O₄Cl₁₆] show an arrangement that differs significantly from known polycationic [Te₈]_n²⁺ chains. The two‐dimensional tellurium network is finally separated by tetrameric, corner‐sharing oxidochloridotantalate anions [(TaO_2/2Cl_4/1)₄]^4– that are firstly observed. The composition of [Te₈]₂[Ta₄O₄Cl₁₆] is confirmed by EDX analysis; its optical band gap is estimated to 1.1–1.2 eV via UV/Vis spectroscopy.     

[Te8][NbOCl4]2 containing an infinite chain‐like {[Te–Te–Te–(Te5)]2+}n polycation

The title compound, [Te₈][NbOCl₄]₂, was obtained as translucent black crystals by reaction of elemental tellurium, niobium(V) chloride and niobium(V) oxychloride in the ionic liquid BMImCl (BMImCl is 1‐butyl‐3‐methylimidazolium chloride). The synthesis was performed in argon‐filled glass ampoules. According to X‐ray structure analysis based on single crystals, the title compound crystallizes with triclinic lattice symmetry and consists of infinite {[Te₈]²⁺}_n cations associated with pyramidal [NbOCl₄]⁻ anions. The novel catena‐octatellurium(2+) cation is composed of Te₅ rings that are linked via Te₃ units [Te—Te = 2.6455 (18)–2.8164 (19) Å]. The composition and purity of [Te₈][NbOCl₄]₂ were further confirmed by energy‐dispersive X‐ray diffraction (EDX) analysis.     

Ionic Association of the Ionic Liquids [C4mim][BF4], [C4mim][PF6], and [Cnmim]Br in Molecular Solvents

Considering the ionic nature of ionic liquids (ILs), ionic association is expected to be essential in solutions of ILs and to have an important influence on their applications. Although numerous studies have been reported for the ionic association behavior of ILs in solution, quantitative results are quite scarce. Herein, the conductivities of the ILs [C_nmim]Br (n=4, 6, 8, 10, 12), [C₄mim][BF₄], and [C₄mim][PF₆] in various molecular solvents (water, methanol, 1‐propanol, 1‐pentanol, acetonitrile, and acetone) are determined at 298.15 K as a function of IL concentration. The conductance data are analyzed by the Lee–Wheaton conductivity equation in terms of the ionic association constant (K_A) and the limiting molar conductance (Λ_m⁰). Combined with the values for the Br^? anion reported in the literature, the limiting molar conductivities and the transference numbers of the cations and [BF₄]^? and [PF₆]^? anions are calculated in the molecular solvents. It is shown that the alkyl chain length of the cations and type of anion affect the ionic association constants and limiting molar conductivities of the ILs. For a given anion (Br^?), the Λ_m⁰ values decrease with increasing alkyl chain length of the cations in all the molecular solvents, whereas the K_A values of the ILs decrease in organic solvents but increase in water as the alkyl chain length of the cations increases. For the [C₄mim]⁺ cation, the limiting molar conductivities of the ILs decrease in the order Br^?>[BF₄]^?>[PF₆]^?, and their ionic association constants follow the order [BF₄]^?>[PF₆]^?>Br^? in water, acetone, and acetonitrile. Furthermore, and similar to the classical electrolytes, a linear relationship is observed between ln K_A of the ILs and the reciprocal of the dielectric constants of the molecular solvents. The ILs are solvated to a different extent by the molecular solvents, and ionic association is affected significantly by ionic solvation. This information is expected to be useful for the modulation of the IL conductance by the alkyl chain length of the cations, type of anion, and physical properties of the molecular solvents.     

Modified Tellurium Subhalides in the New Structure Type [Te15X4]n[MOX4]2n (M = Mo,W; X = Cl,Br)

The reactions of Te₂Br with MoOBr₃, TeCl₄ with MoNCl₂/MoOCl₃, and Te with WBr₅/WOBr₃ yield black, needle-like crystals of [Te₁₅X₄][MOX₄]₂ (M = Mo, W; X = Cl, Br). The crystal structure determinations [Te₁₅Br₄][MoOBr₄]₂: monoclinic, Z = 1, C2/m, a = 1595.9(4) pm, b = 403.6(1) pm, c = 1600.4(4) pm, β = 112.02(2)°; [Te₁₅Cl₄][MoOCl₄]₂: C2/m, a = 1535.3(5) pm, b = 402.8(2) pm, c = 1569.6(5) pm, β = 112.02(2)°; [Te₁₅Br₄][WOBr₄]₂: C2, a = 1592.4(4) pm, b = 397.5(1) pm, c = 1593.4(5) pm, β = 111.76(2)° show that all three compounds are isotypic and consist of one-dimensional ([Te₁₅X₄]²⁺)_n and ([MOX₄]^?)_n strands. The structures of the cationic strands are closely related to the tellurium subhalides Te₂X (X = Br, I). One of the two rows of halogen atoms that bridges the band of condensed Te₆ rings is stripped off, and additionally one Te position has only 75% occupancy which leads to the formula ([Te₁₅X₄]²⁺)_n (X = Cl, Br) for the cation. The anionic substructures consist of tetrahalogenooxometalate ions [MOX₄]^? that are linked by linear oxygen bridges to polymeric strands. The compounds are paramagnetic with one unpaired electron per metal atom indicating oxidation state M^v, and are weak semiconductors.     

Solvent Effects on the 1H-NMR Chemical Shifts of Imidazolium-Based Ionic Liquids

The ¹H nuclear magnetic resonance (¹H-NMR) spectrum is a useful tool for characterizing the hydrogen bonding (H-bonding) interactions in ionic liquids (ILs). As the main hydrogen bond (H-bond) donor of imidazolium-based ILs, the chemical shift (δ_H2) of the proton in the 2-position of the imidazolium ring (H2) exhibits significant and complex solvents, concentrations and anions dependence. In the present work, based on the dielectric constants (ϵ) and Kamlet-Taft (KT) parameters of solvents, we identified that the δ_H2 are dominated by the solvents polarity and the competitive H-bonding interactions between cations and anions or solvents. Besides, the solvents effects on δ_H2 are understood by the structure of ILs in solvents: 1) In diluted solutions of inoizable solvents, ILs exist as free ions and the cations will form H-bond with solvents, resulting in δ_H2 being independent with anions but positively correlated with β_S. 2) In diluted solutions of non-ionzable solvents, ILs exist as contact ion-pairs (CIPs) and H2 will form H-bond with anions. Since non-ionizable solvents hardly influence the H-bonding interactions between H2 and anions, the δ_H2 are not related to β_S but positively correlated with β_IL.     

The mixed valent tellurate SrTe3O8: Electronic lone pair effect of Te

A novel mixed valent tellurium oxide, SrTe₃O₈, has been synthesized and its crystal structure was determined ab initio from powder X-ray diffraction data. This oxide, which crystallizes in a tetragonal unit-cell, P4₂/m space group, with very close a and c cell parameters (6.8257(1) and 6.7603(1) Å, respectively), exhibits a very original structure built up of corner-sharing TeO₆ (Te⁶⁺) octahedra and Te₂O₈ (Te⁴⁺) twin-pyramidal units. The latter ones form [Te₃O₈]_∞ chains running along the [001] and the [110] directions. Besides the four sided tunnels where the Sr²⁺ cations are located, there are very large four sided tunnels running along the c-axis which are obstructed by the electronic lone pairs of the Te⁴⁺ cations.     

Polyoxometalate Ionic Liquids as Self‐Repairing Acid‐Resistant Corrosion Protection

Corrosion is a global problem for any metallic structure or material. Herein we show how metals can easily be protected against acid corrosion using hydrophobic polyoxometalate‐based ionic liquids (POM‐ILs). Copper metal disks were coated with room‐temperature POM‐ILs composed of transition‐metal functionalized Keggin anions [SiW₁₁O₃₉TM(H₂O)]^n? (TM=Cu^II, Fe^III) and quaternary alkylammonium cations (C_nH_{2 n+1})₄N⁺ (n=7–8). The corrosion resistance against acetic acid vapors and simulated “acid rain” was significantly improved compared with commercial ionic liquids or solid polyoxometalate coatings. Mechanical damage to the POM‐IL coating is self‐repaired in less than one minute with full retention of the acid protection properties. The coating can easily be removed and recovered by rinsing with organic solvents.     

Über die Reaktion von Tellur mit Wolframhalogeniden: Synthese und Struktur von Te7WOCl5, einer Verbindung mit einem polymeren Tellur-Kation

On the Reaction of Tellurium with Tungsten Halides: Synthesis and Crystal Structure of Te₇WOCl₅, a Compound with a Polymer Tellurium Cation The reaction of tellurium with WOCl₄ in the presence of a large excess of WCl₆ in a sealed evacuated glass ampoule at 150°C yields beside the main product Te₈(WCl₆)₂ a small amount of Te₇WOCl₅. The crystal structure determination (orthorhombic space group Pcca, lattice parameters at 173 K: a = 2 596.5(9) pm, b = 810.0(3) pm, c = 775.7(2) pm) shows that Te₇WOCl₅ is built of one-dimensional band shaped polymeric tellurium cations, one-dimensional associated pyramidal WOCl₄^? anions and of isolated Cl^? anions. Te₇WOCl₅ can thus be formulated as [Te₇²⁺]_n [WOCl₄^?]_n (Cl^?). The structure is closely related but not isotypic to the bromine containing analogue Te₇WOBr₅. The difference between the two structures lies in different directions of the polar [WOX₄^?]_n chains (X = Cl, Br). The strongly elongated thermal ellipsoid of one tellurium atom is shown to be caused by thermal vibration by determing the crystal structure of Te₇WOCl₅ at three different temperatures (223, 173 and 123 K). All displacement parameters of all atoms can be extrapolated to zero for 0 K.     

Reactivity of the metalloligand [Pt2(µ-S)2(PPh3)4] toward tellurium(II) thiourea complexes: synthesis and structural characterization of the ditellurium(I) derivative [{Pt2(µ-S)2(PPh3)4}2Te2]2+

Abstract

Reaction of the platinum(II) sulfide metalloligand [Pt₂(µ-S)₂(PPh₃)₄] with the tellurium(II) source TeCl₂(tu)₂ (tu?=?thiourea) is dependent on reaction conditions employed. In the presence of added acid, the dominant species observed in the electrospray ionization (ESI) mass spectrum is the tetraplatinum species [{Pt₂(µ-S)₂(PPh₃)₄}₂Te₂]²⁺. This contains the Te₂²⁺ moiety and is related to the previously reported tellurium(I) dithiophosphinate analog [(Ph₂PS₂)₂Te₂]. However, in the absence of acid, considerable degradation of the {Pt₂S₂} metalloligand occurs as evidenced by the formation of the mononuclear complex [Pt{SC(NH₂)NH}(PPh₃)₂]⁺ containing a deprotonated thiourea ligand, together with other thiourea-containing ions, identified by ESI MS. Likewise, attempted use of a fully substituted thiourea, viz. Me₂NC(S)NMe₂ (tmtu) in TeCl₂(tmtu)₂, also resulted in degradation of the {Pt₂S₂} core and detection of the known complex [(Ph₃P)₂PtCl{SC(NMe₂)₂}]⁺. The [{Pt₂(µ-S)₂(PPh₃)₄}₂Te₂]²⁺ cation was isolated with several anions, and unequivocal confirmation of the structure of the complex was obtained by an X-ray structure determination on the BF₄^- salt, which shows the presence of the Te₂²⁺ unit, with the Te–Te bond bridged by two {Pt₂S₂} metalloligands. Density functional theory was used to further probe the Te₂²⁺ bonding interactions in [{Pt₂(μ-S)₂(PPh₃)₄}₂Te₂]²⁺ and the previously reported [(Ph₂PS₂)₂Te₂].     

Synthesis and Crystal Structure of Te6[MCl6] (M = Zr,Hf), Containing a Polymeric Chalcogen Cation (Te62+)n

The reaction of tellurium, tellurium tetrachloride, and ZrCl₄ or HfCl₄, respectively, under the conditions of chemical vapour transport in a temperature gradient 220 → 200 °C yields black crystals of Te₆[ZrCl₆] and Te₆[HfCl₆]. While Te₆[ZrCl₆] is formed almost quantitatively, Te₆[HfCl₆] is always accompanied by neighbored phases such as Te₄[HfCl₆] and Te₈[HfCl₆]. The crystal structures of Te₆[ZrCl₆] (orthorhombic, Pbcm, a = 1095.4(1), b = 1085.2(1), c = 1324.5(1) pm) and Te₆[HfCl₆] (a = 1094.8(2), b = 1086.3(2), c = 1325.0(2) pm) are isotypic and consist of one‐dimensional polymeric (Te₆²⁺)_n cations and of discrete, only slightly distorted octahedral [MCl₆]^2‐ anions (M = Zr, Hf). The cations are build of five membered rings which are connected via single Te atoms to a polymer ‐Te‐Te₅‐Te‐Te₅‐. Out of the six Te atoms of the asymmetric unit of the chain four atoms exhibit two bonds and two atoms exhibit three bonds. The connecting, threefold coordinated Te atoms of the five membered rings carry formally the positive charges. In consistence with the assumption of the presence of throughout localized bonds eH band structure calculations for Te₆[ZrCl₆] show semiconducting behaviour with a band gap of 1.8 eV.     

A square‐planar tellurium(II) complex with Te,Te′‐chelating ligands

While exploring the chemistry of tellurium‐containing dichalcogenidoimidodiphosphinate ligands, the first all‐tellurium member of a series of related square‐planar E^II(E′)₄ complexes (E and E′ are group 16 elements), namely bis(P,P,P′,P′‐tetraphenylditelluridoimidodiphosphinato‐κ²Te,Te′)tellurium(II) (systematic name: 2,2,4,4,8,8,10,10‐octaphenyl‐1λ³,5,6λ⁴,7λ³,11‐pentatellura‐3,9‐diaza‐2λ⁵,4λ⁵,8λ⁵,10λ⁵‐tetraphosphaspiro[5.5]undeca‐1,3,7,9‐tetraene), C₄₈H₄₀N₂P₄Te₅, was obtained unexpectedly. The formally Te^II centre is situated on a crystallographic inversion centre and is Te,Te′‐chelated to two anionic [(TePPh₂)₂N]⁻ ligands in an anti conformation. The central Te^II(Te)₄ unit is approximately square planar [Te—Te—Te = 93.51 (3) and 86.49 (3)°], with Te—Te bond lengths of 2.9806 (6) and 2.9978 (9) Å.     

Ionic Liquids [M3+][A−]3 with Three-Valent Cations and Their Possible Use to Easily Separate Rare Earth Metals

We introduce a simple way to liquify rare earth metals (REM) by incorporating the corresponding cations, in particular Eu³⁺, La³⁺, and Y³⁺, into polyvalent ionic liquids (ILs). In contrast to conventional methods, this is achieved not by transforming them into anionic complexes, but by keeping them as bare cations and combining them with convenient, cheap and commercially available anions (A) in the form [REM³⁺][A ⁻ ]₃. To do so, we follow the COncept of Melting Point Lowering due to EThoxylation (COMPLET) with alkyl polyethylene oxide carboxylates as anions. We provide basic properties, such as glass transition temperatures, viscosities, electrical conductivities, as well as water-octanol partition constants P and show that these ILs have remarkably different properties, despite the similarity of their cations. In addition, we show that the ionic liquids possess interesting luminescent properties as non-conventional fluorophores.     

Isolatable Organophosphorus(III)–Tellurium Heterocycles

A new structural arrangement Te₃(RP^III)₃ and the first crystal structures of organophosphorus(III)–tellurium heterocycles are presented. The heterocycles can be stabilized and structurally characterized by the appropriate choice of substituents in Te_m(P^IIIR)_n (m=1: n=2, R=OMes* (Mes*=supermesityl or 2,4,6‐tri‐tert‐butylphenyl); n=3, R=adamantyl (Ad); n=4, R=ferrocene (Fc); m=n=3: R=trityl (Trt), Mesor by the installation of a P^V₂N₂ anchor in RP^III[TeP^V(tBuN)(μ‐NtBu)]₂ (R=Ad, tBu).     

Synthesis,Structure, and Physico‐optical Properties of Manganate(II)‐Based Ionic Liquids

Several ionic liquids (ILs) based on complex manganate(II) anions with chloro, bromo, and bis(trifluoromethanesulfonyl)amido (Tf₂N) ligands have been synthesized. As counterions, n‐alkyl‐methylimidazolium (C_nmim) cations of different chain length (alkyl=ethyl (C₂), propyl (C₃), butyl (C₄), hexyl (C₆)) were chosen. Except for the 1‐hexyl‐3‐methylimidazolium ILs, all of the prepared compounds could be obtained in a crystalline state at room temperature. However, each of the compounds displayed a strong tendency to form a supercooled liquid. Generally, solidification via a glass transition took place below ?40 °C. Consequently, all of these compounds can be regarded as ionic liquids. Depending on the local coordination environment of Mn²⁺, green (tetrahedrally coordinated Mn²⁺) or red (octahedrally coordinated Mn²⁺) luminescence emission from the ⁴T(G) level is observed. 1 The local coordination of the luminescent Mn²⁺ centre has been unequivocally established by UV/Vis as well as Raman and IR vibrational spectroscopies. Emission decay times measured at room temperature in the solid state (crystalline or powder) were generally a few ms, although, depending on the ligand, values of up to 25 ms were obtained. For the bromo compounds, the luminescence decay times proved to be almost independent of the physical state and the temperature. However, for the chloro‐ and bis(trifluoromethanesulfonyl)amido ILs, the emission decay times were found to be dependent on the temperature even in the solid state, indicating that the measured values are strongly influenced by nuclear motion and the vibration of the atoms. In the liquid state, the luminescence of tetrahedrally coordinated Mn²⁺ could only be observed when the tetrachloromanganate ILs were diluted with the respective halide ILs. However, for [C₃mim][Mn(Tf₂N)₃], in which Mn²⁺ is in an octahedral coordination environment, a weak red emission from the pure compound was found even in the liquid state at elevated temperatures.     

A Facile Route for the Synthesis of Polycationic Tellurium Cluster Compounds: Synthesis in Ionic Liquid Media and Characterization by Single‐Crystal X‐ray Crystallography and Magnetic Susceptibility

An innovative soft chemical approach was applied, using ionic liquids as an alternative reaction medium for the synthesis of tellurium polycationic cluster compounds at room temperature. [Mo₂Te₁₂]I₆, Te₆[WOCl₄]₂, and Te₄[AlCl₄]₂ were isolated from the ionic liquid [BMIM]Cl/AlCl₃ ([BMIM]⁺: 1‐n‐butyl‐3‐methylimidazolium) and characterized. Black, cube‐shaped crystals of [Mo₂Te₁₂]I₆, which is not accessible by conventional chemical transport reaction, were obtained by reaction of the elements at room temperature in [BMIM]Cl/AlCl₃. The monoclinic structure (P2₁/n, a = 1138.92(2) pm, b = 1628.13(2) pm, c = 1611.05(2) pm, β = 105.88(1) °) is homeotypic to the triclinic bromide [Mo₂Te₁₂]Br₆. In the binulear complex [Mo₂Te₁₂]⁶⁺, the molybdenum(III) atoms are η⁴‐coordinated by terminal Te₄²⁺ rings and two bridging η²‐Te₂^2– dumbbells. Despite the short Mo···Mo distance of 297.16(5) pm, coupling of the magnetic moments is not observed. The paramagnetic moment of 3.53 μ_B per molybdenum(III) atom corresponds to an electron count of seventeen. Black crystals of monoclinic Te₆[WOCl₄]₂ are obtained by the oxidation of tellurium with WOCl₄ in [BMIM]Cl/AlCl₃. Tellurium and tellurium(IV) synproportionate in the ionic liquid at room temperature yielding violet crystals of orthorhombic Te₄[AlCl₄]₂.     

Polymere,bandförmige Tellurkationen in den Strukturen des Chloroberyllats Te7[Be2Cl6] und des Chlorobismutats (Te4)(Te10)[Bi4Cl16]

Polymeric, Band Shaped Tellurium Cations in the Structures of the Chloroberyllate Te₇[Be₂Cl₆] and the Chlorobismutate (Te₄)(Te₁₀)[Bi₄Cl₁₆] Te₇[Be₂Cl₆] is obtained at 250 °C in an eutectic Na₂[BeCl₄] / BeCl₂ melt from Te, TeCl₄ und BeCl₂ in form of black crystals, which are sensitive towards hydrolysis in moist air. (Te₄) (Te₁₀)[Bi₄Cl₁₆] is prepared from Te, TeCl₄ und BiCl₃ by chemical vapour transport in sealed evacuated glass ampoules in a temperature gradient 150 ° → 90 °Cin form of needle shaped crystals with a silver lustre. The structures of both compounds were determined based on single crystal X‐ray diffraction data (Te₇[Be₂Cl₆]: orthorhombic, Pnnm, Z = 2, a = 541.60(3), b = 974.79(6), c = 1664.4(1) pm; (Te₄)(Te₁₀)[Bi₄Cl₁₆]: triclinic, P1¯, Z = 2, a = 547.2(3), b = 1321.1(7), c = 1490(1) pm, α = 102.09(5)°, β = 95.05(5)°, γ = 96.69(4)°). The structure of Te₇[Be₂Cl₆] consists of one‐dimensional polymeric cations (Te₇²⁺)_n which form folded bands and of discrete [Be₂Cl₆]^2— anions which form double tetrahedraconnected by a common edge. By a different way of folding compared with the cations present in the structures of Te₇[MOX₄]X (M = Nb, W; X = Cl, Br) the (Te₇²⁺)_n cation in Te₇[Be₂Cl₆]represents a new, isomeric form. The structure of (Te₄)(Te₁₀)[Bi₄Cl₁₆] contains two different polymeric cations. (Te₁₀²⁺)_n consists of planar Te₁₀ groups in the form of three corner‐sharing Te₄ rings connected to folded bands. (Te₄²⁺)_n forms in contrast to the so far notoriously observed discrete, square‐planar E₄²⁺ ions a chain of rectangular planar Te₄ rings (Te—Te 274 and 281 pm) connected by Te‐Te bonds of 297 pm. [Bi₄Cl₁₆]^4— has a complex one‐dimensional structure of edge‐ and corner‐sharing BiCl₇ units.     

Solvothermal Synthesis and Crystal Structure of Te8[U2Br10], Containing a Polymeric Chalcogen Cation (Te82+)n

Under solvothermal conditions, the reaction of Te, TeBr₄ and UBr₅ in SiBr₄ at 200?C yields Te₈[U₂Br₁₀] as silvery crystals. The crystal structure (triclinic, P&1macr;, a = 900.8(4), b = 1205.1(5), c = 1366.0(6) pm, α = 80.93(4)?, β = 76.83(3)?, γ = 78.84(3)?, Z = 2) is built of one‐dimensional polymeric (Te₈²⁺)_n cations consisting of boat‐shaped Te₆ rings, which are linked by Te₂ bridges. The anions [U₂Br₁₀^2‐]_n are also polymeric, consisting of edge sharing UBr₇ pentagonal bipyramids [UBr₃Br_4/2^2‐]_n and contain U(IV). Both chains are parallel to each other and run along the crystallographic a‐axis. The cation represents a formerly unknown isomer of Te₈²⁺ ions. So far, Te₈²⁺ has been known as molecular clusters in Te₈[MCl₆](M = Zr, Hf, Re) and (Te₈)(Te₆)[WCl₆]₄, or in form of linked bicyclic monomers that are present in Te₈[WCl₆]₂. A polymeric chain‐like form closely related to Te₈[U₂Br₁₀] was found in Te₈[Bi₄Cl₁₄].     

Azolate Anions in Ionic Liquids: Promising and Under-Utilized Components of the Ionic Liquid Toolbox

Owing to their ease of synthesis, diffuse positive charge, and chemical stability, 1-alkyl-3-methylimidazolium cations (i.e., [C_nmim]⁺) are one of the most routinely utilized and historically important components in ionic liquid (IL) chemistry. However, while this is a routinely encountered member of the IL family as cations, relatively few workers have explored the versatile chemistry of azoles to allow their use as an anionic component in ILs, as azolates. Azolate anions possess many of the desired properties for IL formation, including a diffuse ionic charge, tailorable asymmetry, and synthetic flexibility, with the added advantages of not relying on halogen atoms for electron-withdrawing effects, as is commonly encountered with IL anions such as hexafluorophosphate. This review explores the 122 azolate-containing ILs known in the literature (prepared from only 39 disparate azolate anions), with a view to highlighting not only their demonstrated utility as an IL component, but the ways in which the larger scientific community may utilize their advantageous properties for new tailored materials.