Selenides polyselenides

LYO/YOU] Lyons, L. E., Young, T. L., Alkaline selenide, polyselenide electrolytes Concentrations, absorption spectra and formal potentials, Aust. J. Chem., 39, (1986), 511-527. Cited on pages 135, 154, 155, 156, 157, 565. 

Bina Selenides. Most biaary selenides are formed by beating selenium ia the presence of the element, reduction of selenites or selenates with carbon or hydrogen, and double decomposition of heavy-metal salts ia aqueous solution or suspension with a soluble selenide salt, eg, Na2Se or (NH 2S [66455-76-3]. Atmospheric oxygen oxidizes the selenides more rapidly than the corresponding sulfides and more slowly than the teUurides. Selenides of the alkah, alkaline-earth metals, and lanthanum elements are water soluble and readily hydrolyzed. Heavy-metal selenides are iasoluble ia water. Polyselenides form when selenium reacts with alkah metals dissolved ia hquid 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. 

Important results and a detailed insight into aqueous chemical deposition processes have been reported and discussed elsewhere for CdSe [248, 249] and ZnS [250, 251] target products. We should note also the work of Davies et al. [252] who described an alternative method for the chemical growth of metal sulfides and selenides on the basis of polysulfide or polyselenide solutions (containing hexa- and tetra-chalcogen anions) formed by the dissolution of sulfur or selenium in hydrazine monohydrate. ... 

Dhingra, S. Kanatzidis, M. G. 1990. The use of soluble metal-polyselenide complexes as precursors to binary and ternary solid metal selenides. Mater. Res. Soc. Symp. Proc. 180 825-830. 

Selenium is soluble in sulphuric acid, forming a green solution which, in the case of the metallic form, probably contains a compound of composition S03Se (p. 338), and in the case of the red amorphous variety, a polymeric form of this compound.8 The presence of selenium does not affect the electrical conductivity of sulphuric aeicl. Dilute aqueous potassium hydroxide dissolves the red variety, producing a solution which probably contains polyselenides in the presence of sodium hydrosulphite, however, only sodium selenide, Na2Se, is obtained.9... 

The selenides of the alkali metals are white when pure, but generally appear pink owing to the presence of free selenium or of polyselenides, as also do the alkali hydroselenides moreover they readily oxidise in air, with separation of selenium. The selenides of the alkaline earth metals are described as pink, but it is questionable whether they have yet been obtained in a pure condition. 

Related investigations on polysulfide and polyselenide anions with iron carbonyl reveal that there is an equally rich chemistry of sulfides and selenides, but it is substantially different from that of the tellurides. For instance, attempts to obtain lighter analogs of 51 under similar... 

The first poly chalcogenide complex, K4USeg, was obtained by a solid-state reaction. It has a molecular sfructure with a distorted dodecahedral anion, [U(Se2)4] , which is isosfructural with the known peroxoanions [M(02)4]" , where M = V, Nb, Ta, Cr (n = 3) or Mo, W (n = 2). Recently, two additional uranium selenides have been synthesized, MU2Se6 (M = K+, Cs+), using a reactive flux method. The oxidation state of the uranium in these compounds was found to be tetravalent. The selenium has two distinct oxidation states, Se and one similar to a polyselenide network. 

Monomeric polyselenide anions [WQ(Se4)2]2 with Q = Se, S, O were synthesized by the reaction of [WSe4]2 and Se8, SeS2, or Se4(NC5Hi0)2, respectively. The crystal structure of [WS(Se4)2] was determined by X-ray analysis. The starting material [MSe4]2 was prepared from W042- and bis(dimethyloctylsilyl) selenide.126... 

Discrete polyselenide chains Se without significant secondary intra- or inter-molecular Se- Se contacts have been structurally characterized for n = 2-8. Crystal structures are known in addition to K5Sc3 for the following binary alkali metal selenides A2Sen in the range n = 2-5 A2Sc2 for A = Na, K,... 

Cadmium Selenide. This compound, or the polyselenide, is responsible for the colour in selenium ruby glass. With some CdS in solid solution it forms the basis of Cd-Se red ceramic (especially vitreous enamel) colours the firing temperature must not exceed about 850°C. The presence of up to 3% V2O5 is claimed to stabilize the colour, blackening in the presence of a glaze or flux containing Pb is caused by the formation of PbSe. Cadmium Silicate. CdSi03, sp. gr. 4.9 m.p. 1240°C. 

However, very often there are deviations from this linearity due to a shift of the position of the band edges under illumination or as a consequence of the reaction with the redox system In order to prevent corrosion, compound semiconductors have often been employed in a saturated solution of their ionic components like sulfides in sulfide solutions with the redox system polysulfide/sul-fide or selenides in the redox system polyselenide/selenide. However, it was found that even under these conditions the crystalline semiconductors can decompose and are transformed either into a surface with numerous lattice defects or into a different polycrystalline material. 

One-bond Se- Se couplings have been observed in a number of diselenides (-1-22 to —67 Hz) and polyselenide anions with charged selenide atoms (250 20 Hz). Two-bond couplings can have large values, particularly in cyclic sulfur-selenium compounds (95-114 Hz). Three-bond couplings (3-16 Hz) have been observed and four-bond couplings up to 16 Hz have been observed in sulfur-selenium cyclic compounds. 

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