How trimethyl(trifluoromethyl)silane reacts with itself in the presence of naked fluoride-a one-pot synthesis of bis([15]crown-5)cesium 1,1,1,3,5,5,5-heptafluoro-2,4-bis(trifluoromethyl)pentenide

Reactions of trimethyl(trifluoromethyl)silane in the presence of naked fluoride proceed up to a temperature of +5 degrees C mainly with formation of [Me3Si(CF3)(2)](-). A further rise of temperature up to about 20 degrees C gives evidence for the formation of a salt with the 1,1,1,2,3,6,6,6-octafluoro-2,4,4,5,5 -pentakis (trifluoromethyl) hex- an-3-ide anion. This intermediate decomposes at room temperature into the 1,1,1,3,5,5,5-heptafluoro-2,4-bis(trifluoromethyl)pentenide anion. The bis([15]crown-5)cesium salt, [Cs([15]crown-5)(2)][(CF3)(2)CCFC(CF3)(2)] has been characterized unambiguously as the stable final product of this reaction sequence. Thermal decomposition of this salt opens a convenient nontoxic route to obtain 1,1,3,3-tetrakis(trifluoromethyl)allene, (F3C)(2)C=C=C(CF3)(2).