Microwave Spectrum of HPF4

Abstract

The microwave spectra of hydrido- and deuteridotetrafluorophosphorane (HPF4 and DPF4) are reported. The molecule is an asymmetric rotor, with the c axis being an axis of twofold symmetry. The spectra, therefore, support the C2υ trigonal bipyramid model, and rule out C3υ and C4υ models. Rotational constants A, B, C (Mc/sec) are, respectively, for HPF4, 6011.29, 4317.42, 3156.22 and for DPF4, 5822.24, 4222.98, 3154.51, with an uncertainty of ± 0.05 Mc/sec. The dipole moment, measured from Stark splittings, is 1.32 ± 0.02 D along the c axis. If the PH bond length for the C2υ trigonal bipyramid model is assumed to be 1.36 ± 0.05 Å, the other parameters are: PF (axial) = 1.594 ± 0.005 Å, PF (equatorial) = 1.55 ± 0.03 Å, ≮ HPFax = 90° ± 4°, ≮ HPFeq = 124° ± 2°. The c axis is along the PH bond, and the axial PF bonds lie in the a, c plane.