Reactions of chloromethyloxirane and dihalopropanols with chalcogens in basic reducing systems

Chloromethyloxirane and 2,3-dibromopropan-1-ol reacted with a solution of selenium or tellurium in the system hydrazin hydrate-potassium hydroxide (K₂Se₂, K₂Te₂) to give allyl alcohol; the reaction was accompanied by regeneration of the initial free chalcogen. 1,3-Dichloropropan-2-ol reacted with selenium in the same system to give oligomeric product having a 2-hydroxypropane-1,3-diyldiseleno monomeric unit, while the reaction with tellurium led to the formation of allyl alcohol and almost complete regeneration of initial tellurium. Probable reaction mechanisms are discussed. Polyselenide oligomers containing a hydroxy group in a monomeric unit were formed in reactions of chloromethyloxirane and 1,3-dichloropropan-2-ol with selenium in the system hydrazine hydrate-2-aminoethanol. Under analogous conditions 2,3-dibromopropan-1-ol was converted into allyl alcohol with regeneration of elemental selenium. Reductive cleavage of polyselenide oligomers gave Se-methyl derivatives of 2-hydroxypropane-1,3-diselenol.     

Polytellurides and Polyselenides – Compounds Containing $_{\infty}^{1}\rm [Te_{6}-Te_{4}]^{4-}$ and [Sn(Se4)3]2− Anions

The reactions of the Zintl phase K₂Cs₂Sn₉ with elemental tellurium and selenium in ethylenediamine have been investigated. From the reaction of K₂Cs₂Sn₉ with elemental tellurium [K‐(2,2,2‐crypt)]₄Te₆Te₄ ( 2 ) and [K‐(2,2,2‐crypt)]₂Sn₂Te₃ ( 3 ) were obtained, whereas the reaction of K₂Cs₂Sn₉ with elemental selenium led to the formation of [K‐(2,2,2‐crypt)]₂Sn(Se₄)₃ ( 4 ) and [K‐(2,2,2‐crypt)]₂Cs₂Sn₂Se₆·2en ( 5 )¹⁾. Compounds 2 , 4 , 5 have been characterized by single crystal X‐ray structure determination.     

Synthesis and structure of tetrakis(phenylenethiourea)tellurium(II) chloride dihydrochloride,C28H26N8S4Cl4Te

Reaction of tellurium(IV) with excess phenylenethiourea(2-mercaptobenzimidazole) in aqueous methanolic hydrochloric acid leads to the formation of Te(II) complex, tetrakis(phenylenethiourea)tellurium(II) chloride dihydrochloride. The characterisation and crystal structure of the complex are reported. The crystals are monoclinic, space group P2₁/c, a = 13.939(5), b = 26.523(9), c = 4.873(2) Å, β = 100.29(4)°, V = 1772.6 ų, M = 872.4, D_c = 1.651 g cm^?3, Z = 2, F(000) = 868, μ(MoK_α) = 1.298 mm^?1. Final R = 0.055 and R_W = 0.056 for 918 independent reflections. The tellurium atom in the molecule lies at the crystallographic centre of symmetry and is bonded to four phenylenethiourea sulphur atoms in a square planar arrangement with TeS(1) = 2.678(6), TeS(2) = 2.674(5) Å and S(1)TeS(2) is 90.5(3)°. The ligand behaves as a thione. Chlorine atoms remain outside the coordination sphere of the Te and stabilise the packing arrangement in the unit cell through hydrogen bondings to nitrogen atoms.     

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.     

TELLURIUM(II)-THIOSEMICARBAZONE COMPLEXES‐A PARALLEL TO THE LIGATION OF THIOUREAS

Abstract

The tellurium(II)-complexes of the type Te(XTSC)₂Cl₂ (I) and Te(XTSC)₄Cl₂ (II), where XTSC=benzaldehyde, acetophenone, salicylaldehyde or 2-hydroxyacetophenone thiosemicarbazone have been isolated. The IR, PMR and CMR spectra of the complexes in conjunction with their elemental analyses and conductance measurements, indicate the formation of a three centre-four electron bond between tellurium and two sulphur atoms of the thiosemicarbazones, trans to each other. These results exhibit for the first time that thiosemicarbazones may ligate with tellurium(II) in a manner parallel to that of thioureas. The square planar and octahedral arrangement of the ligands around tellurium are proposed for I and II type complexes respectively.     

Atmospheric pressure chemical vapour deposition of selenium and tellurium films by UV laser photolysis of diethyl selenium and diethyl tellurium

Excimer laser‐induced photolysis of gaseous diethyl selenium and diethyl tellurium (C₂H₅)₂M (M = Se, Te) is controlled by cleavage of both M? C bonds, it yields C₁–C₄ hydrocarbons (ethene as major product) and results in chemical vapour deposition of selenium films and nanosized tellurium powder. The selenium and tellurium properties were characterized by X‐ray photoelectron spectroscopy and Scanning electron Microscopy techniques. Copyright © 2001 John Wiley & Sons, Ltd.     

The Unique Ambiphilicity of Tellurium in the [MesitylTe(I)(I2)(I3)]− Anion

A first example of an aryltellurium(II) compound with three different bonding modes to iodine featuring covalent and non-covalent bonds such as two orthogonal, ambiphilic σ-hole interactions is introduced: [MesTe(I)(I₂)(I₃)]⁻. It is a member of a series of mesityltellurenyl anions, which are formed during reactions of (MesTe)₂ with ZnI₂, phenanthroline (phen) and iodine. [Zn(phen)₃][MesTe(I)₂] ( 1 ), [Zn(phen)₃][{MesTe(I)-(I)…Te(I)Mes}{MesTeI₂}] ( 2 ) and [Zn(phen)₃][MesTe(I)(I₂)(I₃)][MesTeI₂] ( 3 ) are isolated depending on the amount of iodine used. The products contain tellurium atoms bonded to a variety of iodine species (I⁻, μ₂-I⁻, I₂ and I₃⁻) and are, thus, perfectly suitable to explore the amphiphilic behavior of tellurium(II) and its relevance for the formation of non-covalent bonds, where tellurium acts as both donor and acceptor simultaneously. The character of chalcogen and halogen bonds are evaluated by the combination of crystallographic data and computational methods.     

Structures of Iodophenyltellurium(II) and Diiododi-(β-naphtyl)tellurium(IV)

The reactions between diphenyl ditelluride, (PhTe)₂, or di(β-naphtyl)ditelluride, (β-naphtylTe)₂, with equivalent amounts of iodine have been reinvestigated and the crystal and molecular structures of iodophenyltellurium(II), (PhTeI)₄, and diiododi-(β-naphtyl)tellurium(IV), (β-naphtyl)₂TeI₂, have been determined. The structure of iodophenyltellurium(II) (space group Cc, a = 13.850(5) Å, b = 13.852(3) Å, c = 16.494(6) Å and β = 101.69(2)°, Z = 4) is built up by four PhTeI units which are linked by weak Te–Te interactions with Te–Te distances between 3.152(5) Å and 3.182(4) Å. The angles between the tellurium atoms are approximately 90° giving an almost perfect square. Long range secondary bonds (Te–I: about 4.2 Å) link the tetrameric units to give an infinite two-dimensional network. Iodo(β-naphtyl)tellurium(II) is less stable than the phenyl derivative. Solutions of this compound decompose under formation of elemental tellurium and (β-naphtyl)₂TeI₂. (β-Naphtyl)₂TeI₂ crystallises in the monoclinic space group C 2/c (a = 21.198(6) Å, b = 5.8921(8) Å, c = 16.651(5) Å, β = 114.77(2)°). The tellurium atom is situated on a two-fold crystallographic axis and Te–I and Te–C bond lengths of 2.899(1) and 2.108(7) Å have been determined.     

Exchange effects on the 1H and 31P nmr spectra of cyclodiphosph(III)azane selenides and tellurides

Oxidation of the isomeric cyclodiphosph(III)azanes, (Me₂ NPNBu-t)₂, by selenium and by tellurium gives both isomeric monoselenides but only one monotelluride. Variable temperature ¹H and ³¹P NMR studies provide evidence for restricted rotation about the exocyclic PN bonds, and in the telluride, of exchange of tellurium between the phosphorus atoms.     

Mercapto acid compounds of tellurium(II): stabilization of tellurium---sulfur bonded compounds via intramolecular chelation

A series of tellurium (II0 compounds of general formula (RS)₂Te (R = C₆H₅---, 2-C₁₀H₇---, HOOCCH₂CH₂---, HOOCCH(Me)---, HOOCCH₂---, 2-(HOOC)C₆H₄---, HOOCCH₂CH(COOH)---, NaOOCCH₂CH₂---, NH₄OOCCH₂CH₂---) have been prepared and characterized. The tellurium compounds containing carboxylic acid or salt groups are isolated as stable, light-yellow solids which are soluble in alcohols or in water, and this stability is thought to be due to tellurium---carbonyl oxygen interactions within the molecule. Bis(benzenethio)tellurium---(II) and bis(2-naphthalenethio)tellurium(II) have been synthesized and are unstable both in the solid state and in solution. Nixed derivatives containing one aryl and one sulfide bonded to tellurium (ArTeSCH₂CH₂COOH) have also been prepared, and the reactions of these compounds with dichlorobis(benzonitrile)palladium(II) yield palladium complexes containing two tellurium ligands.     

Osmium(VIII)/palladium(II) catalysis of cerium(IV) oxidation of allyl alcohol in aqueous acid

Summary Catalysis of the Ce^IV-allyl alcohol (AA) reaction in acid solution depends both on the of rate enhancement and product distribution on the catalyst used: Os^VIII results mainly in acrolein, whereas Pd^II gives acrylic acid. The rate laws in the two cases also differ:viz., Equations 1 and 2K₁ is the equilibrium constant of formation of the Os^VIII-allyl alcohol complex and k₁ is the rate constant of its oxidation by Ce^IV; K₂ is the equilibrium constant for the formation of the Ce^IV-Pd^II-allyl alcohol complex and k₂ is its rate constant of decomposition. Rate = K₁k₁[Ce^IV][AA][Os^VIII]/(1+K₁[AA]) (1) Rate = K₁k₁[Ce^IV][Pd^II]/(1+K₂[Ce^IV]) (2)While Os^VIII is effective in H₂SO₄ solution, aqueous HClO₄ is needed for Pd^II. Both reactions proceed through formation of catalyst-allyl alcohol complexes with participation of free radicals. The details of these observations are discussed.     

Complex formation of 1,4,7,10-tetraoxacyclododecane with alkali metal ions studied by 13C spectroscopy

Complex formation of 1,4,7,10-tetraoxacyclododecane (12-crown-4) with lithium, sodium and potassium salts in methanol solution was investigated. The strong influence of complexing on the chemical shift of the single ¹³C NMR line permitted titration of the ligand with alkali metal salts. Concentration stability constants of the complexes were obtained by a computerized iterative least squares method. Na⁺ and K⁺ form both 1: 1 and 1: 2 complexes, log K₁ = 2.1 and log K₂ = 3.8, log K₁ = 1.7 and log K₂ = 2.4 respectively. Li⁺ is complexed weakly. Assuming 1: 1 stoichiometry the complex stability constant is estimated to be < 1.     

Metastable P-Tellurium-Substituted Phosphaalkenes: Formation, 125Te- and 31P-NMR Spectroscopic Characterization,and Decomposition

Abstract

The formation and decomposition of P-tellurium-substituted phosphaalkenes was followed by ³¹P- and ¹²⁵Te-NMR spectroscopy. Acyclic compounds with C?P-Te moieties are in general thermally labile, but bulky substituents enhance the lifetime of a number of species. The P-chlorophosphaalkene (Me₃Si)₂C?PCl (1a) reacts with the disilyltelluride (iPrMe₂Si)₂Te (2) leading to the mixed-substituted telluride (Me₃Si)₂C?PTeSiMe₂iPr 3a which reacts with another equivalent of 1a furnishing the tellurobis(phosphaalkene) [(Me₃Si)₂C?P]₂Te (4a). 4a is a shortlived compound decomposing thermally with precipitation of elemental tellurium, leading to a known diphosphabicyclobutane 5a. In a similar way, the bulkier P-chlorophosphaalkene (iPrMe₂Si)₂C?PCl (1b) reacts with (iPrMe₃Si)₂Te furnishing [(iPrMe₂Si)₂C?P]₂Te (4b), which loses tellurium much more slowly than 4a and can be kept in cold solutions for an extended time. Reactions of in situ-prepared lithium aryltellurolates LiTeAr 6 – 9 [Ar?Ph: 6, Ar?2,4,6-Me₃Ph (?Mes): 7, Ar?2,4,6-iPr₃Ph (?TIP): 8, Ar?2,4,6-tBu₃Ph (?Mes*): 9] with 1a provide P-aryltellurophosphaalkenes 10 – 13, which decompose with the loss of diarylditellurides leading to 5a. After a 2 + 4 cycloaddition trapping experiment of 12 with cyclopentadiene, a metastable P-aryltelluro phosphanorbornene 14 was detected by ³¹P-NMR. Reactions of elemental tellurium with P-phosphanylphosphaalkenes (Me₃Si)₂C?PPR′R′;′ 15 – 17 (R′, R′′?iPr: 15; R′?iPr, R′′?tBu: 16; R′, R′′?tBu: 17) lead to metastable insertion products (Me₃Si)₂C?PTePR′R′′ 18 – 20 that decompose with formation of the tellurobisphosphanes (R′R′′P)₂Te 21 – 23, and of the bicyclic diphosphane 5a, which isomerises thermally to the diphosphabicyclooctane 24. The P-di-i-propylphosphanyl-phosphanorbornene 25 dismutates under the action of tellurium into the symmetric diphosphanes iPr₄P₂ and bis-phosphanorbornene 26. The tellurium-free products 24 and 26 were characterized by X-ray crystallography.     

Electrochemical preparation of thin rhenium-tellurium coatings from chloride-borate electrolyte

The kinetics and mechanism of cathode electrodeposition of thin Re-Te films from a chloride-borate electrolyte containing NH₄ReO₄, TeO₂, HCl, and H₃BO₃ were studied. The region of potentials in which rhenium is electrodeposited together with tellurium was determined by cyclic voltammetry. The combined electrodeposition of rhenium and tellurium occurred with minor depolarization due to the energy liberated during the formation of the Re-Te alloy.     

Influence of electrodeposition conditions on the properties of CdTe films

The results of the influence of electrodeposition conditions on the structural, compositional, optical, and photoelectrochemical properties of CdTe thin films deposited in one-step electrochemical method are presented. The CdTe films were prepared electrochemically from aqueous acidic solution with low ratios of Cd²⁺ ions to Te(IV) ions concentration. Instead of commonly used TeO₂, water-soluble Na₂TeO₃ was used as a source of tellurium ions. The cathodic deposition of CdTe was performed at different constant potentials from solutions containing different cadmium and tellurium ions concentration. As-deposited CdTe thin films were studied by different analytical techniques. The X-ray photoelectron spectroscopy spectra exhibited CdTe formation on the electrode with some amount of tellurium oxides and cadmium oxides. The best quality CdTe deposits, free of TeO₂, were formed in bath containing excess of Cd²⁺ ions and at the potential of ?0.65 V vs. saturated calomel electrode, slightly more positive than E _eq of Cd/Cd²⁺ system. Structural X-ray diffraction studies revealed polycrystallinity of deposits with the highest content of the (111)-oriented cubic (111) form. Optical band gap energy values were found in the range from 1.36 to 1.6 eV for CdTe films prepared at various synthesis conditions. The preliminary photoelectrochemical studies have shown that the variation of the deposition potential as well as bath composition leads to the formation of p- or n-type CdTe films. As-deposited CdTe films were not stable in polysulfide solution under illumination.     

The atomic absorption spectroscopy of Tellurium

Telluiium can be determined by atomic absorption spetroscopy at 2143, 2359, and 2386 A The sensitivities for these lines are in the ratio of 1.9.9 187 With aqueous solutions, a Beckman triple-buiner (air-hydrogen) and a 5-pass optical system, the line 2143 Å has a sensitivity of 0.23 p.p.m , and a detection limit ot 0.076 p.p.m The sensitivities for this line in acqueous and organic solvents, and in air-hydrogen and air-acetylene flames were studied and the optimum conditions determined Where necessary, preconcentration of tellurium by coprecipitation with elemental arsenic, 01 by extraction of K₂Tel₆ or tellurium diethyldithiocarbomate with MIBK can be applied, the latter gives a two-fold enhancement in sensitivity compared with aqueous solutions.     

New CF3 Substituted Phosphorus‐Tellurium Heterocycles

The reaction of trifluormethyl dichlorophosphine (CF₃PCl₂) with sodium telluride Na₂Te or bis(trimethylsilyl) telluride (Me₃Si)₂Te results in the formation of four new phosphorus tellurium heterocycles ( 1–4 ) with the electron withdrawing CF₃ substituent bonded to phosphorus. The telluratriphosphetane (CF₃P)₃Te ( 1 ), telluratetraphospholane (CF₃P)₄Te ( 2 ), telluradiphosphirane (CF₃P)₂Te ( 3 ) and ditelluratriphospholane (CF₃P)₃Te₂ ( 4 ) are characterized by multinuclear (³¹P, ¹⁹F and ¹²⁵Te) NMR spectroscopy. A full analysis of the ¹⁹F NMR spectrum of telluratriphosphetane (CF₃P)₃Te is presented. The new heterocycles are remarkably stable in solution and eliminate only slowly tellurium to form cyclophosphines (CF₃P)_n (n = 3–5).     

Synthesis and polycondensation of some new organic tellurium compounds containing mono- and di-amino groups

Several new and known organic tellurium compounds containing amino groups (i.e. ArTeBr₃, Ar₂Te₂ and Ar₂Te, where Ar= 4-NH₂C₆H₄, 2-NH₂C₆H₄, 4-CH₃CONHC₆H₄ or 2-NH₂-5-NO₂-C₆H₃) were prepared by reacting aminoarylmercury chlorides with tellurium tetrabromide in glacial acetic acid. Bis(4-aminophenyl) telluride and bis(2-amino-5-nitrophenyl) telluride were polymerized with aromatic and aliphatic diacid chlorides (i.e. terephthaloyl chloride and sebacoyl chloride), as well as with toluene di-isocyanate, leading to new organic tellurium polyamides and polyurea. All organic tellurium compounds and their condensation polymers were characterized by elemental analyses, IR, ¹H and ¹³C NMR, and mass spectroscopy. The thermal stabilities of the resulting polymers were determined by thermogravimetric and derivative thermogravimetric techniques. © 1998 John Wiley & Sons, Ltd.     

A Polarographic Study of ϵ-Caprolactam Complexes of Uranium and Tellurium

The polarographic behaviour of uranium and tellurium has been studied in the presence of increasing concentration of complex forming agent viz. ?-caprolactam at pH 4.4 for U(VI) and at pH 10.0 for Te(IV) at μ=0.1 M KNO₃. In both cases the waves have been found to be diffusion controlled and irreversible. The values of kinetic parameters (σπ_a and K°_f,h) have been calculated as a function of the ligand concentration. Method is suitable for the quantitative determination of these metals individually and simultaneously with the effect of diverse ions.