E.S.R. spectra of PF4radicals produced in a single crystal of PF3

Abstract

E.S.R. spectra of PF4 radicals were investigated with single crystals of PF3 made at a low temperature and irradiated with γ-rays. The angular dependence of the spectral lines was satisfactorily analysed in terms of the second-order equations for large couplings of one 31P nucleus and two magnetically equivalent 19F nuclei and of the first-order equation for two 19F nuclei with small couplings. We conclude that the two magnetically equivalent fluorine nuclei occupy the axial positions of the trigonal bipyramidal structure of the PF4 radical and the other two fluorine nuclei are in the equatorial positions. Furthermore, the unpaired electron of the PF4 radical was shown to occupy an orbital consisting mainly of the 2p orbital of each of the two axial fluorine atoms along the F-P-F axis and the 3s and 3p orbitals, directed towards the vacant equatorial position of the central phosphorus atom. The orbital of the unpaired electron can be reasonably represented as a Rundle three-centre non-bonding orbital. The...