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)