Knowledge Bank

The perfluorocyclopropenyl cation, $[FIGURE]$, is the product of the reaction of perfluorocyclopropene with Lewis acids, such as $BF3$. From infrared spectra of the solid compounds, $C3F3+BF4-$ and $C3F\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}+SbF\mathrm{<mrow\; data-mjx-texclass="ORD">6</mrow>}-$, and from Raman spectra of $C3F3+BF4-$ in solution in sulfur dioxide we have observed all but one of the spectroscopically active fundamentals of the $C3F3+$ cation which has $D3h$ symmetry. An overlay normal coordinate calculation for the monofluorocation, the $difluoracation,2$ and the perfluorocation has led to a complete assignment of the fundamentals of the $C3F3+$ cation. With calculated values in parentheses this assignment is (in $cm-1$): $(a1\prime )2013,751;(a2\prime )(800);(e\prime )(1589,998,287;(a2″)(250);(e″)640$. A discussion will be included of the effect of fluorine substitution on the CC stretching force constants.