REACTIONS OF TELLURIUM TETRAHALIDES WITH GLYCOLS

Abstract

Tellurium tetrahalides undergo reaction with glycols to yield three different products: O,O'-dioxotrihalotellurates; bis(alkoxy)dihalotellurium (IV) compounds and hexahalotellurates. The course of the reaction appears to be determined primarily by the nature of the glycol. The structure of dichlorobis(cis- 2-hydroxycyclohexyloxy)tellurium(IV) has been determined crystallographically     

碲的形态分析进展

综述了近年来国内外碲的无机、有机形态分析进展。因碲在环境样品中的含量低、分散,存在形式较多,建立快速、准确的碲形态分析方法是值得进一步探讨的问题。     

火焰原子吸收光谱法测定硒碲混合物中碲的研究

本文建立了酒石酸-硝酸盐酸混酸溶解样品,在王水-酒石酸介质中,采用空气-乙炔火焰在原子吸收光谱仪上测定硒碲混合物中的碲的方法。本实验研究了样品处理方法、乙炔流量、燃烧高度、灯电流、溶液介质等有关工作条件。实验表明碲浓度在1～20ug/mL范围内与吸光度呈良好的线性关系,回归方程为A=0.0229C 0.0009,相关系数0.9998,检出限0.08ug/mL,本方法适合于硒碲混合物中碲的测定,相对标准偏差为0.9%～1.3%,回收率为98%～102%。     

Crystallographic report: Bis(triphenylphosphoranylidene)ammonium phenyltetrachlorotellurate

Unlike most previously described organotetrachlorotellurate complexes, neither secondary Te·Cl interactions nor significant cation–anion interaction are observed in the molecular structure of [Ph₃PNPPh₃][PhTeCl₄]. Copyright © 2005 John Wiley & Sons, Ltd.     

Synthesis and Characterization of Three Coordinate “T-Shaped” Complexes of Tellurium (II) Incorporating a Naphthyl Tellurium Fragment

Several new three coordinate tellurium(II) complexes have been prepared by the addition of dinaphthyl ditelluride (C₁₀H₇)₂Te₂ and a halogen (Br₂ or I₂) to various monodentate ligands known to coordinate through their terminal sulfur or selenium atoms to investigate possible electronic and steric effects associated with a large aryl group. Complexes of the type RTeX(L) are described here [R = naphthyl, X = Br, I, L = thiourea (I (X = Br), II (X = I)), tetramethylthiourea (III), selenourea (IV), tris(dimethylamino)phosphane selenide (V) and N-methylbenzothiazol-2(3H)-thione (VI)]. Evidence of the formation of new complexes is presented through microanalytical data and multinuclear NMR spectroscopy in addition to single crystal X-ray diffraction studies of (I) and (III). Structures are described in detail along with a comparison with related Te (II) complexes.     

Coexistence of Tellurium Cations and Anions in Phosphonium-Based Ionic Liquids

Elemental tellurium readily dissolves in ionic liquids (ILs) based on tetraalkylphosphonium cations even at temperatures below 100 °C. In the case of ILs with acetate, decanoate, or dicyanamide anions, dark red to purple colored solutions form. A study combining NMR, UV-Vis and Raman spectroscopy revealed the formation of tellurium anions (Te_n)²⁻ with chain lengths up to at least n=5, which are in dynamic equilibrium with each other. Since external influences could be excluded and no evidence of an ionic liquid reaction was found, disproportionation of the tellurium is the only possible dissolution mechanism. Although the spectroscopic detection of tellurium cations in these solutions is difficult, the coexistence of tellurium cations, such as (Te₄)²⁺ and (Te₆)⁴⁺, and tellurium anions could be proven by cyclic voltammetry and electrodeposition experiments. DFT calculations indicate that electrostatic interactions with the ions of the ILs are sufficient to stabilize both types of tellurium ions in solution.     

Newer Aspects in Synthetic Methodology of Pyridyl Chalcogen (E═Se/Te) Compounds

Abstract

A number of synthetic protocols for the synthesis of symmetrical dipyridyl chalcogenides/dichalcogenides have successfully been developed by employing cheap, economically viable and eco-friendly reagents. The reductive cleavage of Se–Se and Te–Te bond in these versatile compounds conveniently have been achieved and a number of hitherto unknown chelating seleno/telluro ethers with varying back bones have been prepared employing appropriate alkylating agents.     

Non-isothermal studies on crystallization kinetics of tellurite 20Li<Subscript>2</Subscript>O-80TeO<Subscript>2</Subscript> glass

Structural and thermal properties of the 20Li₂O-80TeO₂ glass were studied using X-ray diffraction analysis and differential scanning calorimetry techniques to understand and control the crystallization process on this glass. The γ-TeO₂, α-TeO₂ and α-Li₂Te₂O₅ phases were identified during the crystallization in this glass. Activation energies and Avrami exponent n were calculated from non-isothermal measurements for glasses with different particle size. The mean values of Avrami exponent were obtained for glasses with 63–75 and 45–63 μm particle sizes such as , but glasses with particle size 38–45 μm and smaller than 38 g,m presented .     

Determination of Tellurium by Instrumental Photon Activation Analysis

Abstract

Tellurium has been determined at milligram and submilligram levels in the presence of uranium by a strictly instrumental photon activation ¹²¹ analysis procedure. The 575 keV gamma ray of Te was measured. At a decay time of three weeks, this gamma ray peak was interference-free. As little as 0.4 mg of tellurium was determined and the method evidences that sensitivity would increase with irradiation time.     

A Regioselective Synthesis of Novel Functionalized Organochalcogen Compounds by Chalcogenocyclofunctionalization Reactions Based on Chalcogen Halides and Natural Products

The regioselective synthesis of novel functionalized condensed organochalcogen compounds by chalcogenocyclofunctionalization reactions based on chalcogen halides and the natural products thymol and carvacrol has been developed. The reactions of selenium dibromide with allyl thymol and allyl carvacrol proceeded in methylene chloride at room temperature in the presence of NaHCO₃ affording bis[(7-isopropyl-4-methyl-2,3-dihydro-1-benzofuran-2-yl)methyl] and bis[(4-isopropyl-7-methyl-2,3-dihydro-1-benzofuran-2-yl)methyl] selenides in 90–92% yield. Similar sulfides were obtained in 70–72% yields by the reaction of sulfur dichloride in chloroform under reflux. Trihalotellanes containing the same organic moieties were synthesized from allyl thymol, allyl carvacrol and tellurium tetrachloride or tetrabromide in quantitative yields. Corresponding functionalized ditellurides were prepared in 91–92% yields by the reduction of the trichlorotellanes with sodium metabisulfite in two-phase solvent system. The comparison of reactivity of sulfur, selenium and tellurium halides in chalcogenocyclofunctionalization and distinguishing features of each reaction were discussed.     

Studies on the Selective Syntheses of Sodium Ditelluride and Dialkyl Ditellurides

Studies on the selective synthetic method for dialkyl ditellurides 1, a representative class of organyl tellurium compounds, were presented. Considering the difficulty in conducting previous harsh reactions and in suppressing the formation of dialkyl tellurides 2 as side products, we optimized reaction conditions for selective syntheses of sodium ditelluride and the corresponding dialkyl ditellurides 1. We reduced tellurium to sodium ditelluride by using NaBH₄ and subsequently, treated the obtained sodium ditelluride with alkyl halides (RX) to give the target compounds 1. Consequently, by applying various alkyl halides (RX) we achieved the selective syntheses of dialkyl ditellurides 1 (13 examples with 4 new compounds) in modest to good yields. We also suggested the mechanistic pathways to dialkyl ditellurides 1.     

Tellurium-Modified Nucleosides,Nucleotides, and Nucleic Acids with Potential Applications

Tellurium was successfully incorporated into proteins and applied to protein structure determination through X-ray crystallography. However, studies on tellurium modification of DNA and RNA are limited. This review highlights the recent development of Te-modified nucleosides, nucleotides, and nucleic acids, and summarizes the main synthetic approaches for the preparation of 5-PhTe, 2′-MeTe, and 2′-PhTe modifications. Those modifications are compatible with solid-phase synthesis and stable during Te-oligonucleotide purification. Moreover, the ideal electronic and atomic properties of tellurium for generating clear isomorphous signals give Te-modified DNA and RNA great potential applications in 3D crystal structure determination through X-ray diffraction. STM study also shows that Te-modified DNA has strong topographic and current peaks, which immediately suggests potential applications in nucleic acid direct imaging, nanomaterials, molecular electronics, and diagnostics. Theoretical studies indicate the potential application of Te-modified nucleosides in cancer therapy.     

Literature Highlights

Abstract

The synthesis of several 1-oxa-6-heteraspiro[2.5]octanes is reported herein for the first time. Stereochemical analysis via NMR studies and a single crystal X-ray diffraction analysis of 6-phenyl-1-oxa-6-phosphaspiro[2.5]octane 6-sulfide have been completed and provide the basis for correlations of structures for other members of the families yet unknown. Epoxidation of cis-2,6-diphenyl-4-thianone with dimethyl-oxosulfonium methylide in DMSO led, surprisingly, to a tertiary alcohol, presumably via ring opening of the expected intermediate epoxide. This is the first example of this type of ring opening in the presence of this base but the reaction time was longer than that normally employed in this process.

Since the family members of the parent spiro[2.5]octanes are rare, an X-ray diffraction analysis was performed on 6-phenyl-1-oxa-6-phosphaspiro[2.5]octane 6-sulfide. This analysis revealed a space group of Pna2₁ with cell dimensions of: a=13.056(3) A, b=14.268(3) Å, and c=6.1522(11) Å. The phosphorinane ring assumes a slightly flattened chair conformation with the phenyl-P bond being equatorial and the P[dbnd]S bond being axial. The plane of the epoxide is virtually coincident with a pseudo-mirror plane through P(6), C(3), C(9) and S(15). The phenyl group is rotated out of this plane by 28.2°. Although the P—C distances (ring carbons) are 1.813(3) Å and 1.819(3) Å, respectively, and appear to be about normal, the P-phenyl bond of 1.813(3) Å is longer than in a few model systems. The C(3)—O(1) bond in the epoxide is axial or rather pseudo axial. Ring deformations are consistent with a few model epoxides the structures of which have been identified.     

Study on the Thermodynamic Stabilities of Te-Substituted Di-n-butyltellurium Ylide

SincethediscoveryofphosphoniumylidebyWittig',carbanionsstabilizedbyadjacentfifthorsixthgrouponiumionshavebeendevelopedasavaluablereactiveintermediate.However,despitethegreateffortsinylidechemistryinthepastfewdecades',relativelylittleisknownaboutthethermodynamicstabilitiesofylidecarbanions.Itiswellknowthatthequantitativemeasuresofthecarbanionstabilityhavecontributedagreatdealtothedevelopmentoforganicchemistry,thereforeitshouldbeexpectedthattheknowledgeaboutylidestabilitywillalsoprovidavaluableg…     

Cytotoxic Activity of Ammonium Tellurates

The cytotoxic activity of a series of methylammonium tellurates on human fibrosarcoma HT-1080, mouse hepatoma MG-22A, and mouse fibroblasts 3T3 cell lines is described. The role of tellurates as free radical regulators is discussed.     

2,5-Bis-(butyltelluro) thiophene as a convenient precursor for the synthesis of 2,5-bis-(acetylenic) thiophenes

Both symmetrically and unsymmetrically substituted 2,5-bis-(acetylenic) thiophene derivatives were obtained in good yields under mild conditions through palladium-catalyzed cross coupling reaction of 2,5-bis-(butyltelluro) thiophene 2 and terminal alkynes. The methodology represents a general and efficient protocol for carrying out the synthesis of thiophene derivatives with potential biological activities.     

Palladium(II) chloride catalyzes the cross-coupling reaction of 2,5-bis-(butyltelluro)-furan and 1-alkynes

Palladium(II) chloride catalyzed the cross-coupling reaction of 2,5-bis-(butyltelluro) furan and terminal alkynes yielding both symmetrically and unsymmetrically substituted 2,5-bis-acetylenic furan derivatives. The methodology represents a general and efficient protocol for carrying out the synthesis of furan derivatives with potential biological activities.