Sulfides, Selenides, and Tellurides

Double Decomposition.—Many binary compounds may be regarded as salts of definite binary acids as well as compounds formed by the union of two elements. Among such compounds are the metallic halides, sulfides, selenides, tellurides, and peroxides. Many salts of these acids may be made by neutralizing a soluble base with the appropriate acid a much larger number may be made by the method of double decomposition (Exercise 15). 

The nickel arsenide (NiAs) structure is also based on an hep array in this case, the cations form the backbone lattice, and the larger anions occupy both octahedral sites. This structure, also associated with metal sulfides, selenides, tellurides, and antimonides, is only adopted for weakly ionic compounds. Since the octahedral sites are extremely close to one another, purely ionic compounds would be much too unstable due to strong anion-anion repulsions. 

Formation of Sulfides, Selenides, Tellurides, and Seleno-cyanates. When O-acyl thiohydroxamates are decomposed in the presence of disulfides, diselenides or ditellurides, mixed sulfides. 

Commonly used II-VI compounds include zinc sulfide, zinc selenide, zinc telluride, cadmium sulfide, cadmium telluride, and mercury cadmium telluride. These materials are not as widely used as the III-V compounds, one reason being that it is difficult to achieve p-type doping. Mercury cadmium telluride is used extensively in military night sights, which detect in the 8-13 im spectral band (a similar material, platinum silicide, is being developed for that purpose). The major applications ofCVD II-VI compounds are found in photovoltaic and electroluminescent displays. 

Colloidal sulfide, selenide, telluride, phosphide, and arsenide semiconductor particles are prepared by the controlled precipitation of appropriate aqueous metal ions by H2S, H2Se, H2Te, PH3, and AsH3, respectively. Colloids are stabilized, typically, by sodium poly-phosphate. A large number of experimental parameters determine the size, size distribution, morphology, and chemical composition of a semiconductor particles in a given preparation. Concentrations, rates, and the order of addition of the reagents the counterions selected ... 

This chapter has been devoted to the coordination chemistry of titanium and has made no attempt to describe the more basic chemistry of this element. References to alloys, to the simple halides and oxyhalides, the oxides, sulfides, selenides, tellurides, nitrides, azides, phosphides, arsenides and antimonides are well reviewed by Clark,14 and the recent text by Greenwood and Earnshaw180 contains a good section on titanium. 

The cadmium chalcogenide semiconductors (qv) have found numerous applications ranging from rectifiers to photoconductive detectors in smoke alarms. Many Cd compounds, eg, sulfide, tungstate, selenide, telluride, and oxide, are used as phosphors in luminescent screens and scintillation counters. Glass colored with cadmium sulfoselenides is used as a color filter in spectroscopy and has recendy attracted attention as a third-order, nonlinear optical switching material (see NONLINEAR OPTICAL MATERIALS). Dialkylcadmium compounds are polymerization catalysts for production of poly (vinyl chloride) (PVC), poly(vinyl acetate) (PVA), and poly(methyl methacrylate) (PMMA). Mixed with TiCl4, they catalyze the polymerization of ethylene and propylene. 

SULFIDES and SULFOSALTS (sulfides, selenides, tellurides arsenides, anti-monides, bismuthides sulfarsenites, sulfantimonites, sulfbismuthites, etc.)... 

Actinide sulfides, selenides, and tellurides are also known. The sulfides and selenides are generally isostruc-tural, but not with the analogous tellurides. The thermal stability of these compounds decreases in the order sulfides > selenides > tellurides. These compounds are usually prepared via direct reaction of finely divided actinide metal powder with the chalcogen at about 400-600°C. Semimetallic behavior and nonstoichiometry are observed for these compounds. 

The iodo-formates obtained as described above are useful intermediates, which can be further transformed into cyclic amines, cyclic sulfides, cyclic tellurides, and cyclic selenides by the sequences outlined in Scheme 49. A variety of heterosteroids have been synthesized from the corresponding steroidal... 

No other oxide phases below MO2 have been established but a yellow hydroxide , precipitated by alkali from aqueous solutions of chromium(II), spontaneously evolves H2 and forms a chromium(III) species of uncertain composition. The sulfides, selenides and tellurides of this triad are considered on p. 1017. 

Selenides and tellurides are, again, broadly similar to the sulfides in structure and properties. 

Ethyleneimine reacts with (p-tolylsulfonyl)acetylene to give only the (Z)-product 115 via trans addition (equation 91), while primary and secondary aliphatic amines afford ( )-products76. With nonterminal acetylenes such as l-(ethylsulfonyl)-l-propyne, the reactions of ethyleneimine, n-propylamine and f-butylamine give mixtures of ( )- and (Z)-adducts. The double conjugate addition of sodium sulfide, selenide and telluride to bis(l-propynyl)sulfone (116) produces heterocycles (117) as illustrated in equation 9277. 

The Alkaline-Earth Oxides, etc.—The observed and calculated inter-atomic distances for the alkaline-earth oxides, sulfides, selenides and tellurides are given in Table VIII. Except for the magnesium com-... 

The effect of deformation is shown in the sulfide, selenide and telluride of lead. Especially interesting is the decrease in the crystal radius in the series Mn++, Fe++, Co++, Ni++ there must then come an increase when the shell is completed, at Zn++, with the radius 0.74 A. 

It is also shown that theoretically a binary compound should have the sphalerite or wurzite structure instead of the sodium chloride structure if the radius ratio is less than 0.33. The oxide, sulfide, selenide and telluride of beryllium conform to this requirement, and are to be considered as ionic crystals. It is found, however, that such tetrahedral crystals are particularly apt to show deformation, and it is suggested that this is a tendency of the anion to share an electron pair with each cation. 

K. C. Mills, Thermodynamic Data for Inorganic Sulfides, Selenides and Tellurides, Butterworths, London, 1974. 

Rare earth sulfides, selenides, and tellurides show semiconducting properties and have potential for application in thermoelectric generation. Thin film chalcogenides of various rare earths have been prepared by multisource evaporator systems [233]. 

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