Selenides Potassium selenocyanate

Triphenylphosphine selenide, potassium selenocyanate, 3-methyl-2-selenoxobenzothiazole sodium 0,0-diethyl phosphorotelluronate," 0,0-dialkyIphosphoroselenoic acid salts" and benzenese-lenocarboxamide, have all been reported as reagents capable of one-step deoxygenation of epoxides. 

The advantage of this method is that it avoids the use of hydrogen selenide, necessary for the preparation of selenourea from cyanamide (14). Benzoylselenourea is synthesized by the method of Douglass (24) by the action of potassium selenocyanate On benzoyl chloride in acetone solution. 

Selen-verbindung, /. selenium compound, -wasserstoff, m, hydrogen selenide. -was-serstoffsaure, /. hydroselenic acid, -wismut-glanz, m. guanajuatite. -zelle, /. selenium cell, -zyanid, n. selenium cyanide seleno cyanate. -zyankalium, n. potassium selenocyanate. 

Selenocyanic Acid, HCNSe, may be prepared in solution by decomposing the lead salt (obtained by treating potassium selenocyanate with lead acetate) with hydrogen sulphide.3 It is stable only in neutral or alkaline solution. Selenocyanuric acid has been obtained 4 as a red amorphous powder by the action of cyanuric chloride on sodium selenide and subsequent precipitation by acids. 

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

A similar exchange reaction produced the 1 1 complexes of phenyl tellurium thiocyanate with ethylenethiourea1, when the phenyl tellurium chloride complex was treated with potassium thiocyanate in aqueous methanol. However, the phenyl tellurium chloride -selenourea adduct and potassium selenocyanate yielded bis[phenyIteUuro] selenium3. Phosphane selenides also coordinate to phenyl tellurium halides3. 

Selenetane is a pungent liquid obtained in low yield by treating 1,3-dibromo-propane with sodium selenide. Substituted selenetanes have been obtained by treatment of 1,3-dihalopropanes (e.g., 644) with potassium selenide or the cyclic monocarbonate of pentaerythritol with potassium selenocyanate. 3-Hydroxyselenetane 645 [ H nmr 5 3.6 (7=5.8) (H ) 3.85 (OH), 3.9-4.2(m) (H )ppm] is obtained by electrolysis in a diaphragm cell of chloromethyloxirane (epichlorohydrin) in the presence of selenium powder. It is also obtained by treatment of l,3-dibromo-2-propanol with NaSeH. Tetravalent, four-membered selenuranes are formed by treatment of 3,3-dimethylselentane with bromine at low temperature, and by treatment of the 1,1-dibromoselenetane... 

Finely divided free selenium reacts with mercury vapor to produce black mercury selenide. Suitable reagent paper is prepared by soaking filter paper in a solution of potassium selenocyanate (KCNSe), draining, and exposing to an atmosphere of hydrogen chloride (hood ). The potassium selenocyanate solution is readily prepared by vigorously shaking potassium cyanide solution with an excess of pure selenium powder in a stoppered flask. 

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. " ... 

Alcoholic potassium hydroxide when warmed with the selenocyanate in the absence of air converts it into the selenophenol (selenide) ... 

Selenocyanates (RSeCN), which are employed for the synthesis of selenides and selenoesters, are usually derived from selenenyl halides and cyanide ion (or silyl cyanate) [38 k, 40]. Alkylation of potassium selenolate (KSeCN) with alkyl halides is an alternative means of preparation of aliphatic selenocyanates (Scheme 15.13)... 

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