Tellurium in organic chemistry—I : A novel synthesis of biaryls

Treatment of bis(aryl)tellurium dichlorides or diaryl tellurides with degassed Raney nickel readily affords the corresponding biaryls. The bis(aryl)tellurium dichlorides were prepared from TeCl₄ and the appropriate aromatics, with or without a Lewis acid as a catalyst, depending on the reactivity of the aromatic. The diaryl tellurides were prepared by reduction of the dichlorides with hydrazine. Attempts to prepare unsymmetrical dichlorides frequently resulted in exchange reactions (RTeCl₃ + R′H → R′TeCl₃ + RH).     

Organotellurium(IV) complexes: synthesis and molecular structure of 2,6-diacetylpyridine (C,N,O) tellurium(IV) trichloride

The reaction of TeCl₄ with 2,6-diacetylpyridine in methylene chloride or tetrahydrofuran gives a new type of organotellurium (IV) compound. An X-ray structure determination showed that the organic radical bonds to the tellurium as a tridentate ligand via a methylene carbon of one of the acetyl groups, the pyridine nitrogen, and the carbonyl oxygen of the second acetyl group. Analogous organotellurium trichloride complexes involving C,O coordination have been formulated for the condensation products of TeCl₄ with 2-acetylcyclohexanone and 3-acetyl-7-methoxycoumarin, while C,N coordination occurs in the condensation product of TeCl₄ and 2-acetylpyridine.     

Tetravalent Tellurium Ligands

Oxidative addition of TeCl₄ to Vaska's complex gave the trichlorotelluronium complex [IrCl₂(TeCl₃)(CO)(PPh₃)₂] (structure depicted), which contains a rare example of a structurally characterized tetravalent tellurium ligand. The coordination at the Te^IV center is—in full agreement with the VSEPR model—distorted trigonal bipyramidal.     

Electrochemistry of tellurium(IV) in KCl−AlCl3 melts

The reduction of Te(IV) at tungsten electrodes in basic and neutral KCl?AlCl₃ melts has been studied in the temperature range from 300 to 400°C using cyclic voltammetry and differential pulse polarography. In basic melts Te(IV), present as TeCl₆^2? and TeCl₅^?, is reduced to soluble Te(II) species, which can be further reduced to elementary tellurium insoluble in tungsten. The divalent species are stabilized by increasing the temperature. From the pCl^? dependence of the reduction process, Te(II) in basic melts is suggested to be present as TeCl₃^? and TeCl₂. In neutral melts a third oxidation state (possibly monovalent tellurium) is formed when Te(II) is reduced.     

anti-Markovnikov addition of tellurium tetrachloride to trimethyl ethynyl silane

An investigation of the TeCl₄ interaction with trimethyl ethynyl silane 1 in CHCl₃ has shown that anti-Markovnikov adduct [Z-1-(trimethylsilyl)-2-chlorovinyl]tellurium trichloride is formed as the only product. In time, it is hydrolyzed to give [Z-1-(trimethylsilyl)-2-chlorovinyl]tellurium (hydroxy) dichloride which, in turn, is dehydrated to afford bis[(2-chloro-1-trimethyl-silylvinyl)dichlorotellurium]oxide. These data revealed that the reaction studied was the first example of anti-Markovnikov syn-addition of TeCl₄ to terminal acetylenes. A computed simulation of the TeCl₄ interaction with ethynyl silane 1 in a gas state using PES method did not reveal dominating orientation of the addition but showed the conditions at which anti-Markovnikov addition can occur and which were probably met in carrying out the reaction in CHCl₃.     

The ligational behaviour of thiosemicarbazones and semicarbazones with tellurium(IV)—reactions with TeCl4

The reactions of thiosemicarbazones and semicarbazones of benzaldehyde, salicylaldehyde, acetophenone and 2-hydroxyacetophenone with TeCl₄ give the complexes LTeCl₄, (LH)TeCl₃ or (LH)Te₂Cl₇ (L = semicarbazone or thiosemicarbazone). The structural features of these tellurium derivatives are explored by IR, ¹H and ¹³C NMR, and conductance (in acetonitrile) measurements, and structures based on an octahedral arrangement of ligands around tellurium are proposed. The presence of facial and meridian isomers in equilibrium is indicated in some cases. The complexation occurs through S/O, the nitrogen of the > CN group and O⁻ (if present on benzene ring). The (LH)Te₂Cl₇ species seem to have chlorine bridged and octahedrally coordinated tellurium.     

Dicationic Tellurium Analogues of the Classic N‐Heterocyclic Carbene

The synthesis and comprehensive characterization of the first dicationic tellurium analogues of N‐heterocyclic carbenes (NHCs) has been reported, in both the +2 and +4 oxidation states. For the +2 oxidation state, a base‐stabilized form of TeCl₂ is used as the starting material. The dications are isolated by means of halide metathesis and the solid‐state structures confirm the previously calculated diimine bonding arrangement. For Te^IV, a diamine is used in a high‐yielding dehydrohalogen coupling reaction from TeCl₄. The dicationic NHC analogue is isolated in a base‐stabilized form through halide abstraction and subsequent coordination by pyridine.     

First example of the <Emphasis Type="Italic">anti</Emphasis>-Markownikoff addition of tellurium tetrachloride to terminal acetylene,trimethyl ethynyl silane

(μ₂-Oxo)-bis[dichloro(Z-2-chloro-1-trimethylsilylethenyl)tellurium(IV)] (III) was prepared by electrophilic addition of TeCl₄ to trimethylethynylsilane in CHCl₃ at room temperature. The reaction is the first example of the anti-Markownikoff type addition of TeCl₄ to terminal acetylenes affording as an intermediate the 1:1 adduct [Z-1-(trimethylsilyl)-2-chlorovinyl]tellurium trichloride (II). The latter is converted into III by a sequence of successive reactions of hydrolysis and dehydration. The structure of compound III was proved by the of multinuclear (¹H, ¹³C, ²⁹Si, ¹²⁵Te) NMR spectroscopy and XRD analysis. Compound III is the first example of structurally characterized C-TeCl₂-O fragment.     

The Structure of Tetrakis(pentafluorophenyl)tellurium(IV), Te(C6F5)4

Tetrakis(pentafluorophenyl)tellurium(IV), Te(C₆F₅)₄, was prepared from the reaction of TeCl₄ and Mg(C₆F₅)Br. Crystallization of the crude product from n‐pentane at ?25 °C gave suitable single crystals. The title compound crystallizes in the monoclinic space group P2₁/c (Z = 8) with two independent molecules per unit cell.     

Über die Kronenetherkomplexe [K(15-Krone-5)2]3[Sb3I12], [TeCl3(15-Krone-5)][TeCl5] und [TeCl3(15-Krone-5)]2[TeCl6]

On the Crown Ether Complexes [K(15-Crown-5)₂]₃[Sb₃I₁₂], [TeCl₃(15-Crown-5)][TeCl₅], and [TeCl₃(15-Crown-5)]₂[TeCl₆] Orange-coloured crystals of [K(15-crown-5)₂]₃[Sb₃I₁₂] are formed in the reaction of potassium iodide with antimony triiodide and 15-crown-5 in acetonitrile solution. An X-ray structure determination reveals severe disorder of the crown ether molecules, which coordinate to the potassium atoms in a sandwich array; so only the [Sb₃I₁₂]^3? ion and the potassium positions were ascertained. The anion is a centrosymmetric trimer (symmetry C_2h), which can be understood as central SbI₆^3? ion, coordinated by two SbI₃ molecules. (Space group C2/m), Z = 2, 3263 observed, independent reflections, R = 0.06, lattice dimensions at 20°C: a = 2541.1 pm, b = 1441.7 pm, c = 1588.4 pm, β = 113.33°. The tellurium complexes [TeCl₃(15-crown-5)] [TeCl₅] and [TeCl₃(15-crown-5)]₂[TeCl₆] are prepared by reaction of TeCl₄ with 15-crown-5 in acetonitrile solution, forming yellow-green crystals sensitive to moisture. They are characterized by their i.r. spectra.     

Die Kristallstruktur von [TeCl3(15-Krone-5)]SbCl6

The Crystal Structure of [TeCl₃(15-crown-5)]SbCl₆ The title compound is synthesized by the reaction of tellur tetrachloride, 15-crown-5 and antimony pentachloride in acetonitrile solution, forming colourless crystals, which were characterized by IR spectroscopy and an X-ray structure determination. Space group Pnma, Z = 4, 1966 observed unique reflections, R = 0.072, R_w = 0.052. The compound forms ions [TeCl₃(15-crown-5)]⁺ and SbCl₆^?; in the cation the tellurium atom is eightfold coordinated by the three chlorine atoms and the five oxygen atoms of the crownether molecule (Te? O bond lengths 266 and 279 pm).     

Tellurium Chloride Complexes in Nonaqueous Solutions

Tellurium(IV) complexes (R₄N)₂[TeCl₆] (T6), (R₄N)[TeCl₅] (T5), and (R₄N)[TeCl₄OH] (T4), where (R₄N)⁺ is tetrabutyl, tetraoctyl, and trialkyl benzyl ammonium cations, were synthesized. Tellurium distribution between aqueous HCl solutions and trialkyl benzyl ammonium chloride solution in caprylic acid was studied. The ¹²⁵Te NMR spectra of aqueous HCl solutions of tellurium have a single averaged peak, whose chemical shift (CS) depends on the acid concentration. ¹²⁵Te NMR spectroscopy has shown that the T4 complex in nonaqueous solutions is kinetically inert and the ligand exchange with the T6 and T5 complexes is retarded. In contrast, the T5 and T6 complexes, when simultaneously present in nonaqueous solutions, rapidly exchange ligands. ¹²⁵Te NMR, IR, Raman, and UV spectroscopic studies have shown that under standard conditions, the reaction (Bu₄N)[TeCl₅]+Bu₄NCl = (Bu₄N)₂[TeCl₆] G⁰ = -19.1(1 ± 0.3) kJ/mol and H⁰ = -6.5(1 ± 0.2) kJ/mol) takes place in methylene chloride solution. The symmetry groups of the synthesized complexes in the solid state and CSs for tellurium solutions (0.2 gatom/liter Te) in methylene chloride were determined: O_h and –58 ppm for T6; C_4v and +75 ppm for T5; and C_3v and +54 ppm for T4 (CS = 0 for a 0.2 mol/liter TeO₂ solution in 11.4 mol/liter HCl).     

Binuclear complexes of 4-methoxyphenyltellurium trichloride with variably linked diphosphine disulfide ligands

Four neutral ligands of the diphosphine disulfide type with different central linking groups [(CH₂)₄, (CH₂)₆, (C₆H₄)₂, and HN-(C₆H₄)-NH] were reacted with 4-methoxyphenyltellurium trichloride in dichloromethane. The crystallization of products afforded crystals consisting of binuclear addition complexes of 4-MeOC₆H₄TeCl₃ with corresponding ligands. The ligands are coordinated to Te(IV) centres through weak Te–S bonds. The coordination of both tellurium atoms in each complex is pseudo-octahedral, built of the TeCl₃S tetragonal basis and the aryl group and the lone pair of electrons in axial positions. The weak donating properties of sulfur atoms are reflected in shortening of the trans-positioned Te–Cl bonds.     

Regioselective reactions of sulfur, selenium and tellurium chlorides with allyl trimethyl silane

Electrophilic addition of SCl₂, SeCl₂ and SeCl₄ to 2 equivalents of allyl trimethyl silane proceeds regioselectively to give bis[2-chloro-3-(trimethylsilyl)propyl] sulfide, selenide and selenium dichloride, respectively. The reaction with TeCl₄ affords only diallyl tellurium dichloride. The structures of the compounds were confirmed by ¹H, ¹³C, ⁷⁷Se and ¹²⁵Te NMR techniques.     

Reactions of tellurium(IV) chloride,aryl-, diaryl-, and triaryl tellurium(IV) chlorides with pyrimidine-2-thiols

1-Substituted 4,4,6-trimethyl-1H, 4H-pyrimidine-2-thiol(L), whose substituents are C₆H₅ ( 1 ), p-CH₃OC₆H₄ ( 2 ), p-O₂NC₆H₄ ( 3 ), n-C₄H₉ ( 4 ), and NH₂ ( 5 ), react with TeCl₄, ArTeCl₃ (Ar = C₆H₅, 4-CH₃OC₆H₄, or 4-C₂H₅OC₆H₄), Ph₂TeCl₂, and Ph₃TeCl, resulting in TeCl₃(L–H), ArTeCl₂(L–H), Ph₂TeCl₂.L, and Ph₃TeCl.L types of compounds. Elemental analyses, molecular weights, conductances in solutions, IR, and ¹H and ¹³C NMR spectral data of these compounds suggest that, in all of them, the pyrimidine-2-thiols ligate through sulfur only. In the first two types of derivatives, the thiol form of L reacts with tellurium moieties, resulting in the liberation of HCl. On the basis of these data TeCl₃(L-H) appears to exist as a dimer in which two Te atoms are probably 5-coordinated and are bridged by two Cl. Tellurium in ArTeCl₂(L-H), Ph₂TeCl₂.L, and Ph₃TeCl.L also appears to be 5-coordinated. IR data suggest that the Te–S bond in Ph₂TeCl₂.L is weak and, therefore, because of partial dissociation, the molecular complexes exhibit lower molecular weights in CH₃CN. Ph₃TeCl.L in acetonitrile behaves as a 1:1 electrolyte. Attempts to synthesize N-, S-, and Te-containing heterocycle ring compounds from TeCl₃( 1/2 -H) and ArTe( 1/2 -H)Cl₂ did not succeed.     

高分子载体Lewis酸催化剂——四氯化碲-聚苯乙烯复合物

<正> 高分子催化剂作为功能性高分子的重要组成部分具有许多独特的优点和功能,是目前催化剂研究的发展方向之一,日益受到重视。 Neckers等将AlCl_3与聚苯乙烯反应制成的高分子载体催化剂,对酯化、缩醛等反应有较好的催化作用,我们也曾制备了一系列聚苯乙烯与强Lewis酸的复合物催化剂,如聚苯乙烯-五氯化锑复合物(Ps-SbCl_5)、聚苯乙烯-四氯化钛复合物(Ps-TiCl_4)、聚苯乙烯-四氯化锡复合物(Ps-SnCl_4)、聚苯乙烯-三氯化铁复合物(Ps-FeCl_3)等,它们具有较高的稳定性和良好的催化效能.为了研究弱Lewis酸与高分子载体的复合能力以及它们是否还具有催化活性,为了研究各种Lewis酸用高分子载体固载化的规律     

Adducts of tellurium and organotellurium(IV) chlorides with transition metal chelates of tetradentate schiff bases

Summary Coordinative interaction between tellurium tetrachloride or aryltellurium trichloride and transition metal chelates of tetradentate Schiff bases has yielded bimetallic molecular adducts of the general formula R_nTeCl_4–n · ML [n = 0 or 1, R = Ph,p-MeOC₆H₄ orp-EtOC₆H₄, M = nickel(II) or copper(II) and L^2– dianion of the Schiff bases derived from salicylaldehyde oro-hydroxyacetophenone and ethylenediamine]. The i.r. spectral and magnetic measurements on the complexes in the solid state indicate coordination of the metal chelates to tellurium(IV)via two phenolic oxygens. Planarity about the transition metal ion is thus retained.     

Perfluororganotellur-Verbindungen: Neue Untersuchungen zur Darstellung von Te(Rf)2 und CH3TeRf (Rf = C2F5, C3F7, C6F5)

Perfluoroorgano Tellurium Compounds: New Investigations on the Preparation of Te(R_f)₂ and CH₃TeR_f (R_f = C₂F₅, C₃F₇, C₆F₅) Methyl(perfluoroorgano) tellurium and bis(perfluoroorgano) tellurium compounds are synthesized in high yields from the photochemical or the thermal reactions of (CH₃)₂ Te with perfluoroorgano iodides in the presence of (C₂H₅)₃N. They are isolated in pure states. Another general method for the preparation of bis(perfluoroorgano) tellurium is the thermal reaction of TeCl₄ with bis(perfluoroorgano) mercury. The preparations and properties of the partially new compounds are described.     

über die Existenz von Mischkristallen im System CuCr2Se4-ZnCr2Se4

Raman Spectra of the System PCl₅? TeCl₄ Raman spectra of solid and molten PCl₅? TeCl₄ mixtures have been recorded. The solid 1:1 mixture contains the compound nPCl₄ + (TeCl₅^?)_n. In the molten state there are different fragmentation equilibria between the polymeric (TeCl₅)^?_n, TeCl₆^2?, and lower charged units. The spectra of TeCl₄ rich samples indicate different species like Te₃Cl₁₃^?, Te₂Cl₁₀^2?, and (TeCl₅^?)_n. In such melts the equilibria are shifted to lower charged oligomeres and TeCl₅^?.     

Zum chemischen Transport von ZrO2 und HfO2 mit den Transportmitteln Cl2 und TeCl4

On the Chemical Transport of ZrO₂ and HfO₂ with the Transport Agents Cl₂ and TeCl₄ ZrO₂ und HfO₂ migrate in a temperature gradient (1100 → 1000°C) with the transport agent either Cl₂ or TeCl₄ by endothermic transport reaction. At experiments in silica glass tubes with TeCl₄ well developed crystals of ZrO₂ could be obtained. From HfO₂, as from both oxides using Cl₂, only powdery products are formed. The transport rates with TeCl₄ were higher than with Cl₂. The influence of different pressures was examined for the transport of ZrO₂ with TeCl₂ with thermochemical model calculations the expected transport rates could be investigated. The large correspondence between calculated and experimental received values speaks for a true interpretation of the transport observations.