Tellurides, liquid

Methyl l-Methoxyltellurobenzoate)1 A solution of 0.171 g (1 mmol) 2-methoxybenzoyl chloride in 8 ml tetrahydrofuran is added to 0.174 g (1 mmol) of freshly prepared sodium telluride (liquid ammonia method). The mixture is stirred at 0° for 1 h and then filtered. The solvent is evaporated from the filtrate under reduced pressure. The red, oily residue is cooled to — 63° under nitrogen and mixed with 2 ml (32 mmol) iodomethane. The mixture is warmed to — 30° and stirred at this temperature for 2 h. The excess iodomethane is evaporated under reduced pressure below 0°. The residue is treated with 5 ml dichloromethane, the black mixture is filtered, and the filtrate evaporated under reduced pressure below 0° to give yellow crystals yield 84% m.p. 25°. 

Selenium and Tellerium Tantalum is attacked by selenium and tellurium vapours at temperatures higher than 80°C. Only slight attack is observed on the metal by liquid selenides and tellurides of ytirum, the rare earths, and uranium at temperatures of 1300 to 2100°C, and tantalum is considered to be a satisfactory material in which to handle these intermetallic compounds. 

The source is usually a temperature-stabilized ceramic filament operating around 1500K. The detector in FTIR is usually a deuterium triglycine sulphate (DTGS) detector, although in RAIRS experiments the liquid nitrogen-cooled mercury cadmium telluride (MCT) detector is employed. 

The experiments described here were performed with a Digilab FTS40 Fourier transform instrument, with a liquid nitrogen-cooled Mercury Cadmium Telluride, (MCT), detector. The instrument is provided with a computer for data acquisition, storage and mathematical treatment. P-polarized incident light was obtained by means of an A1 wire-grid polarizer supported on a BaF2 substrate. 

FT-IR microspectroscopy is a new nondestructive, fast and rehable technique for solid-phase reaction monitoring. It is the most powerful of the currently available IR methods as it usually requires only a single bead for analysis, thus it is referred to as single bead FT-IR [166]. (See also Chapter 12 for further details). The high sensitivity of the FT-IR microscope is achieved thanks to the use of an expensive liquid nitrogen-cooled mercury cadmium telluride (MCT) detector. Despite the high cost of the instrument, this technique should become more widely used in the future as it represents the most convenient real-time reaction monitoring tool in SPOS [166, 167]. 

Diorganyl tellurides have low molecular mass and are colourless or yellowish liquids with an unpleasant and penetrating odour. Dimethyl teUuride is a metabolite of tellurium and tellurium compounds in a variety of living organisms, including humans. Higher dialkyl tellurides and most diaryl tellurides are solids with low melting points (diphenyl telluride is a liquid). 

Dialkyl tellurides (generalprocedure) Elemental Te is added in 0.5 g portions to a well-stirred solution of Na in liquid NHj until the solution decolourizes, forming a colourless suspension (2 g-atom Na/1 g-atom Te). The quantities of the materials are chosen to give a suspension of -0.7 M. The alkylating agent is added dropwise in 10% excess to the suspension of NUjTe. The reaction mixture is stirred until the NHj evaporates. H2O is then added, the mixture extracted with ether and the ethereal solution worked up in the usual manner. 

When the alkylating agent is insoluble in liquid ammonia, as in the case of long-chain compounds, an organic solvent is added to the sodium telluride residue after evaporation of the ammonia. Some cyclic and steroidal tellurides have been prepared from sodium telluride in ethanol and the appropriate dihalides. ... 

Methyl (3-hydroxy)propyl telluride (typical procedure) MeTeLi. A suspension of Te powder (12.8 g, 0.1 mol) in THE (100 mL) is frozen in a liquid N2 bath, and then MeLi (66.7 mL of a 1.5 M solution in ether, 0.1 mol) is injected into the flask. The mixture is allowed to thaw and is stirred magnetically for a further 30 min at room temperature. The resulting yellow-orange solution is stored under N2 and used within 2 h. 

With sodium sulphide hydrate (general procedure) The diorganyltellurium dihalide is mixed with a 15 times molar excess of Na2S 9H2O and the mixture heated at 95-100°C for 10 min or more, until aU the solid has melted. Sufficient HjO is added to dissolve the sulphide and then the mixture is filtered if the obtained telluride is a solid, or extracted with a solvent (ether or petroleum ether) if the telluride is a liquid. The products are purified by crystallization or distillation. Yields are high or quantitative (except for diphenyl telluride or di-p-tolyl telluride). 

Organyl tellurols are very unstable compounds owing to their extreme sensitivity to oxygen, giving the corresponding ditellurides. The first short-chain alkyltellurols (C1-C4) have been isolated as yellow liquids with an obnoxious odour, from the reaction of aluminium telluride and hydrogen telluride, respectively, with alcohols and aUcyl bromides. Aryltellurols seem not to have been isolated. As shown in Sections 3.1.3.2 and 3.2.2, aryl tellurolates are... 

Alkyl vinyl tellurides can also be prepared by a sequential reaction of divinylic tel-lurides with lithium and alkyl halides in liquid ammonia. ... 

Vinylic tellurides (generalprocedure) Elemental Te (0.6 g, 5.0 mmol) is added to a solution of the vinylic magnesium bromide (5.5 mmol) in THE (10 mL) under reflux and N2 atmosphere, and the reflux maintained for 20 min. The mixture is allowed to reach room temperature and then treated with n-butyl bromide (0.7 g, 5.0 mmol). After stirring for 10 min, the reaction mixture is cooled at 0°C, treated dropwise with saturated aqueous NH4CI, extracted with ether, dried (MgS04) and then evaporated. Kiigelrohr distillation of the residue under vacuum gives the vinyl alkyl tellurides as yellow liquids. 

Methyl phenylethynyl telluride (typical procedure). To NaNH2 (from 6.0 g, 0.26 mol Na) in liquid NHj (250 mL) is added phenylacetylene (25 g, 0.25 mol) dropwise, and then Te powder (30 g, 0.24 mol) in small portions, stirring well for 30 min. Methyl iodide (36 g, 0.25 mol) is added over 20 min to the tellurolate solution. The NHj is then evaporated, the residue extracted with ether and the ether solntion washed with HjO and dried (MgS04). The residue is distilled under vacnum, giving the product (28 g (46%) b.p. 122-124°C/2 torr). 

Synthesis of compound A.A solution of 1,3-dibromopropane (10.1 g, 0.05 mol) in benzene (100 mL) was added to a solution of sodium telluride (NajTe 17.4 g, 0.1 mol) in ethanol (700 mL). After 3 h sodium borohydride (3.8 g, 0.1 mol) was further added to the mixture to produce sodium propane-1,3-ditellurolate, and then to the mixture was added a solution of the dibromopropane (10.1 g, 0.05 mol) in benzene (100 mL). The whole mixtnre was stirred at room temperature for 2 h. After usual work-up, the crude products were purified by silica gel column chromatography (eluent n-hexane/benzene) to afford compound A, which was further purified by preparative liquid chromatography. 

Binary Selenides. Most binary selenides are formed by heating selenium in the presence of the element, reduction of selenites or selenates with carbon or hydrogen, and double decomposition of heavy-metal salts in aqueous solution or suspension with a soluble selenide salt, eg, Na2Se or (NH Se [66455-76-3]. Atmospheric oxygen oxidizes the selenides more rapidly than the corresponding sulfides and more slowly than the tellurides. Selenides of the alkali, alkaline-earth metals, and lanthanum elements are water soluble and readily hydrolyzed. Heavy-metal selenides are insoluble in water. Polyselenides form when selenium reacts with alkali metals dissolved in liquid ammonia. Metal (M) hydrogen selenides of the M HSe type are known. Some heavy-metal selenides show important and useful electric, photoelectric, photo-optical, and semiconductor properties. Ferroselenium and nickel selenide are made by sintering a mixture of selenium and metal powder. 

FTIR Microspectroscopy.3 A microscope accessory coupled to a liquid-nitrogen-cooled mercury-cadmium-telluride (MCT) detector can be used to obtain an IR spectrum. This is possible in both the transmission and reflectance modes. Several beads are spread on an IR-transparent window (NaCl, KBr, diamond) and possibly flattened via a hand-press or a compression cell. The IR beam is focused on a single bead using the view mode of the microscope. The blank area surrounding the bead is isolated using an adjustable aperture, and a spectrum is recorded using 32 scans (<1 min). A nearby blank area of the same size on the IR transparent window is recorded as the background. 

When the gas is kept in sealed tubes a deposit of tellurium gradually forms on the walls. This dissociation does not appear to be accelerated by light, as is the case with liquid hydrogen telluride (see before), since it occurs just as rapidly in the dark.10... 

A photoconductive detector is a semiconductor whose conductivity increases when infrared radiation excites electrons from the valence band to the conduction band. Photovoltaic detectors contain pn junctions, across which an electric field exists. Absorption of infrared radiation creates electrons and holes, which are attracted to opposite sides of the junction and which change the voltage across the junction. Mercury cadmium telluride (Hg,. Cd/Te, 0 < x < 1) is a detector material whose sensitivity to different wavelengths is affected by the stoichiome-try coefficient, x. Photoconductive and photovoltaic devices can be cooled to 77 K (liquid nitrogen temperature) to reduce thermal electric noise by more than an order of magnitude. 

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