Infrared and Raman spectra, conformational stability, structural parameters, ab initio calculations and vibrational assignments of aminodifluorophosphine

Infrared spectra (4000–50 cm−1) have been recorded for three isotopomers of aminodifluorophosphine, H2NPF2, H215NPF2 and D2NPF2, of the gases. The Raman spectra of all three molecules were recorded of the liquids. To support the vibrational assignment MP2(full) ab initio calculations with the 6-31G(d) basis set were carried out to predict the fundamental vibrational frequencies, infrared intensities, Raman activities, depolarization values and infrared band contours. Additional ab initio calculations employing a variety of basis sets with and without diffuse functions have been used to predict the conformational stability, structural parameters and centrifugal distortion constants. These predictions are compared to previously reported experimental values when available. The adjusted r0 structural parameters have been obtained by systematically fitting the MP2(full)/6-311+G(d) predicted values with the previously reported rotational constants for five isotopomers obtained from the microwave study. The difference in the two NH distances is 0.003 Å which is much smaller than the value of 0.021 Å previously reported. The bonding around the nitrogen atom is effectively planar which is consistent with the previously reported structural information from the microwave study but differs from the reported slightly pyramidal bonding obtained in the electron diffraction investigation. The adjusted r0 heavy atom distances and angles are: r(PF) = 1.587(3); r(NP) = 1.649(3) Å; ∠FPF = 94.7(5); ∠NPF = 100.6(5)°. Vibrational assignments are given for H2NPF2, H215NPF2 and D2NPF2 which are supported by ab initio MP2/6-31G(d) calculations. These results are compared to the corresponding quantities of some similar molecules.