Potassium diselenide

Parkinson, B.A., Heller, A., and Miller, B., Effects of cations on the performance of the photoanode in the n-gallium arsenide/potassium selenide (K2Se)-potassium diselenide (K2Se2)-potassium hydroxide/carbon semiconductor liquid junction solar cell, /. Electrochem. Soc., 126,954,1979. 

The diselenides, RSe.SeR, are prepared by the interaction of potassium diselenide and dialkyl sulphates or alkyl halides ... 

Diselenodiacetic acid is obtained as already mentioned or by treating potassium chloroacetate with potassium diselenide,... 

Diselenodipropionicacid, C02H.CH2.CH2.Se.Se.CH2.CH2.C02H, is prepared from j8-chloropropionic acid and potassium diselenide, or by treating 6-selenocyanopropionic acid with hot hydrochloric acid. It melts at 137° C. 

By allowing potassium diselenide to react with diazotiscd j8-naphthylamine. 

Facile synthesis of macrocycles 234 and 235 containing a phosphine oxide group and selenium atoms was recently developed <2001J(P1)1140>. Pulverized Se(0) was reduced with KBH4 in absolute alcohol to produce a mixture of potassium selenide and potassium diselenide, which reacted with 232 to give a mixture of diselenaphosphoninone 235 and selenaphosphocinone 234. 

A facile synthetic method for a series of macrocycles containing a phosphine oxide group and two selenium atoms was published < 2001J(P 1)1140>. Macrocycles 263 were obtained by a one-pot reaction from 235, which was generated in situ by the previously described procedure from a mixture of potassium selenide and potassium diselenide and dibromides 232. Without isolation, diselenide 235 was treated with potassium borohydride and sodium hydroxide to form a diselenide anion 262, which was allowed to react with various dibromides to give macrocycles 263 with moderate yields. 

Alternatively, macrocycle 263b (R = (CH2)3) was synthesized by the reduction of 1,2-diselenacyclopentane 264 with potassium borohydride, followed by the condensation of the resulting potassium diselenide 265 with dibromide 232 in 27% yield. Two related macrocycles 267 and 269, containing two ethereal oxygen atoms, were also synthesized by the similar condensation from corresponding diols 266 and 268 in 26% and 22% yields, respectively <2001J(P1)1140>. 

Diphenyl diselenide has been prepared by disproportionation of phenyl selenocyanate in the presence of potassium hydroxide" or ammonia/ and by air oxidation of benzeneselenol. The preparation of benzeneselenol is described in an earlier volume in this series/ In the present procedure phenylselenomagnesium bromide formed from phenylmagnesium bromide and selenium is oxidized directly to diphenyl diselenide with bromine/ Thus the liberation of the malodorous and toxic hydrogen selenide and benzeneselenol is avoided. Benzeneselenenyl chloride has been prepared by thermal elimination of ethyl chloride from ethyl phenyl selenide di-chloride/ by thermal elimination of chlorine from phenylselenium trichloride," and by chlorinolysis of diphenyl diselenide with either sulfuryl chloride " or chlorine. " ... 

Phenyl selenides Diphenyl diselenide, 125 Selenocyanates Potassium selenocyanate, 286 Other selenides... 

Dimethyl selenide, (CH3)2Se.—An intimate mixture of selenium and amorphous phosphorus (5 2) is heated, and the black mass powdered and heated in a retort with concentrated sodium hydroxide and potassium methyl sulphate. The mixture foams and a yellow liquid distils over. This is separated from the water and fractionated to remove dimethyl diselenide, which is present in small quantity. 

This selenide may be obtained as follows (1) Phosphorus pentaselenidc (P2Se5) is treated with alcoholic sodium hydroxide until sodium selenide is produced, air being excluded during the operation. Benzyl chloride is then added and the mixture heated under reflux. Evaporation away of the solvent yields white needles of the selenide, together with yellow scales of the diselenide.8 (2) Potassium selenosulphate is... 

Di-m-aminophenyi diselenide, (NH2.C6H4)2Se2, may be obtained in three ways (1) The foregoing compound is reduced by an alkaline solution of sodium sulphide. (2) m-Nitrophenyl selenocyanate is reduced by tin and hydrochloric acid. (3) Diazotised m-nitroaniline is treated with potassium selenocyanate.5 The dihydrochloride crystallises from dilute hydrochloric acid in yellow grains formed of small needles melting with decomposition at 291° to 292° C. (corr.).6 It readily... 

Di-p-ethoxyphenyl diselenide, (C6H4.OC2H5)2Se2, is obtained by oxidising p-ethoxyselenophenol with dilute potassium hydroxide solution. It forms brilliant yellow laminae, M.pt. 65° C. 

Dibenzyl diselenide, (C6H5.CH2)2Se2.—This compound may be obtained in a variety of ways (1) Sodium selenide is heated for several hours under reflux with benzyl chloride in alcoholic solution.2 (2) A good yield of the diselenide results when a solution of selenium in sodium sulphide or sodium hydroxide is shaken on a machine with benzyl chloride.3 (3) Potassium selenosulphate is shaken with the calculated quantity of benzyl chloride in the cold. (4) An alcohol solution of potassium benzyl selenosulphate is treated with an excess of iodine, and the diselenide remaining in solution is precipitated by the addition of water. The precipitate is collected immediately and recrystallised from alcohol, since the presence of iodine appears to aid decomposition, with deposition of selenium, and it is also necessary to wash the crystals with water to remove any traces of hydriodic acid before drying the product.4 (4) An aqueous solution of potassium benzyl selenosulphate is subjected to electrolysis, using a current of 0 25 to 0 5 ampere, the method of operation being similar to that used for di-p-nitrobenzyl diselenide. 

Di-p-nitrobenzyl diselenide,6 (N02.C6H4.CH2)2Se2.—An alcoholic solution of iodine is added to a solution of potassium p-nitrobenzyl selenosulphate in alcohol until the colour of the iodine persists water is then added to precipitate the last traces of diselenide. The latter is then recrystallised from alcohol containing a drop of sulphurous acid,... 

Benzyl chloride and potassium selenocyanate give benzyl selenocyanate, which yields a para-compound on nitration, the latter also being obtained by the condensation of p-nitrobenzyl chloride with potassium selenocyanate. The strength of the nitric acid and the conditions of the nitration determine the resulting products in the case of chlorophenyl and tolyl compounds. Nitric acid (density 1 4) at 8° C. converts p-tolyl selenocyanate into di-2-nitro-p-tolyl diselenide and 2-nitro-p-tolylselenimc acid, whereas acid of density 1 5 at -10° C. yields 2-nitro-p-tolyl selenocyanate and a small amount of 3-nitro-p-tolyl selenocyanate. 

This is obtained in the usual manner from diazotised p-toluidine and potassium selenocyanate it yields large transparent crystals of characteristic odour, M.pt. 55° to 56° C., readily soluble in most organic solvents and easily volatile in steam. Di-p-tolyl diselenide occurs with it as a by-product. When p-tolyl selenocyanate is boiled with alcoholic sodium hydroxide, di-p-tolyl diselenide results. Nitration 4 at -10° C. with nitric acid of density 1-5 yields principally 2-nitro-p-tolyl selenocyanate, yellow needles, M.pt. 69° to 70° C., and in much smaller amount 3-nitro-p-tolyl selenocyanate, yellow needles, M.pt. 150° C. If nitric acid of density 1 41 be used at 3° C., a mixture of di-2-nitro-p-tolyl diselenide and 2-nitro-p-tolueneseleninic acid results. 

Dinaphthylselenoxide, C10H7.SeO.C10H7, occurs when 8 -dinaphthyl diselenide, in acetic acid, is oxidised by potassium dichromate. From alcohol it is deposited as colourless needles, M.pt. 134° C. 

The foregoing nitric acid solution of polymerised c /cZoselenopropane after removal of the oxalic acid gives a viscous residue. After treatment with sodium acetate, addition of potassium iodide precipitates the brick-red diselenodi-iodide. The di-iodide occurs when hydriodic acid acts on trimethylenediselenious acid or when a chloroform solution of C2/cZotrimethylene diselenide is treated with iodine. It dissolves in warm chloroform or benzene, but is very sparingly soluble in acetone or alcohol it melts to a red liquid at 124° C. 

The foregoing diselenocyanate and diselenide both dissolve readily in nitric acid and the solution on concentration yields white needles of the dinitrate. This decomposes at 112° C., dissolves readily in water, and the solution, when treated successively with sodium acetate and potassium iodide, yields brick-red trimethylenediselenodi-iodide. 

This product crystallises from acetic acid as orange-red plates, M.pt. 212° C., which give a green solution in alcoholic potassium hydroxide. This solution on standing in air deposits the yellowish-red diselenide. The selenophenol dyes wool orange-red. 

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