1369. Pentafluoroethyl derivatives of selenium

Abstract

Welcnzan and Regev 761 1 1369. Pentajluoroethyl Derivatives of Selenium B y N. WELCMAN and (MRs.) H. REGEVSeveral pentafluoroethyl derivatives of selenium have been prepared by the use of the mercurial, (C,F,Se),Hg, or preferably the diselenide, (C,F,) ,Se,, as starting materials. Reactions of these new compounds were studied, and some of their physical properties are described. Pentafluoroethyl selenyl trichloride is stable under excess pressure of chlorine, and the tertiary pentafluoroethylselenyl amine seems to be unstable. PERFLUOROALKYL derivatives of metals and non-metals can be prepared mainly by two types of reaction. (1)The direct reaction between the element and the respective perfluoroiodoalkane.(2) The thermal interaction of the element and a heavy-metal salt of the appropriate perfluoroalkyl acid.Most perfluoroalkyl compounds of many elements, notably those of phosphorus, arsenic, antimony, and sulphur, were prepared by the first meth0d.l Bistrifluoromethyl mono-and di-selenide were also prepared by the interaction of trifluoroiodomethane and selenium.2 Bis-pentafluoroethyl and -heptafluoropropyl mono-and di-selenides, on the other hand, were prepared by the action of mercuric or silver propionate and butyrate, respectively, on selenium metal p ~w d e r . ~ Bis-trifluoromethyl and -pentafluoroethyl diselenide were separated from the respective original reaction mixtures by fractional vacuum distillation, but the corresponding separation of bisheptafluoropropyl diselenide was not fea~ible.~ Bispentafl uoroethyl diselenide reacted readily with the stoicheiometric amount of chlorine to form pentafluoroethylselenyl chloride, and with excess of chlorine it gave pent afluoroethylselenyl trichloride. This is a pale yellow solid, stable only under pressure of chlorine, and on exposure to the atmosphere it gives a colourless, volatile solid, soluble in water to give an acid solution.The reaction between the diselenide and mercury was stoicheiometric and gave the mercurial, (C2F5Se),Hg, a white, crystalline solid, m. p. 3 9 4 0 " . This mercurial reacted at room temperature instantaneously with iodine to give the diselenide, but the reaction (a)

Some Pseudohalide Derivatives of Perfluoralkyl Selenides

“…All starting materials, such as silver salts of perfluoroalkyl acids and the corresponding perfluoroalkyl selenium chlorides, were prepared by methods previously described [2,3]. Infrared spectra were recorded on a Perkin-Elmer model 131 Infracord, either in the gaseous phase or, for solid materials, in KBr discs.…”

“…There are relatively few works dealing with the specific field of pseudohalide derivatives of fully fluorinated alkyl or aryl sulphides or selenides. The question of the existence and stabi.lity of these compounds arose as a consequence of the earlier preparation of several perfluoroalkyl monohalides of selenium and the differences found between them [1,2,3). Thus, the reacti.on of bis-trifluoromethyl and pentafluoroethyl monoselenide with chlorine partly resulted in the formation of trifluoromethyl selenium mono-and tri-chloride, respectively, whereas the same reaction with the heptafluoropropyl analog gave no trichloride.…”

Trifluormethylselenyl‐Verbindungen des N, P und As

“…Wahrend in der Chemie der CF,S-Gruppe alle Verbindungen der Reihe (CF,S)nNH,_n (n = 1, 2,3) [I] synthetisiert werden konnten und praparativ interessante Ausgangsverbindungen darstellen, kennt man vom CF,Se-Rest keine entsprechenden Amine ; lediglich (C,F,Se),NH [2] ist hergestellt und charakterisiert worden. Setzt man CF,SeBr mit NH, bei -20°C im Molverhaltnis 3:4 um, SO erhLlt man (CF,Se),N, das noch (CF,Se),NH, CF,SeNH, und CF,SeSeCCF, ent-Iialt, gemiiJ3 :…”