MICROWAVE SPECTRUM OF HPF4

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, trigonal bipyramid model, and rule out 63 and 64,, models. Rotational constants A, B, C (Me/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 Me/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 62, trigonal bipyramid model is assumed to be 1.36±0.05 A, the other parameters are: PF(axial) = 1.594±0.005 1, PF(equatorial) =1.55±0.03 A, <£HPFax = 90°±4°, £HPFea=124°±2°. The c axis is along the PH bond, and the axial PF bonds lie in the a, c plane.