Knowledge Bank

The gas phase Raman spectrum of the $\nu 7$ fundamental of $PF5$ has been observed under spectral resolutions approaching 1 $cm-1$. With the use of a two dimensional harmonic oscillator basis set and a potential function of the form $V(p,\phi )=1/2ap2-b\cos (3\phi )p3+cp4$, an adequate fit to the observed spectrum was obtained. In addition, this potential enabled us to estimate an axial-equatorial fluorine interchange barrier of 1371 $cm-1$ (3.92 Kcal/mole). As one might expect, the other $MF5$ ($D3h$) gas phase molecules such as $AsF5$ and $VF5$ should show a $\nu 7$ spectrum very similar to that of $PF5$. We are currently studying $AsF5$ and $VF5$ and find this to be the case.