Spectra and structure of organophosphorus compounds: XLIX. Microwave, infrared, and Raman spectra, electric dipole moment, molecular structure, and ab initio calculations of dimethylphosphonothioic fluoride

The microwave spectra of (CH3)2PSF, (CH3)(CD3)PSF, (CD3)2PSF, and (CH3)2P34SF have been investigated from 20.0 to 40.0 GHz. Botha-type R branch andc-type Q branch transitions have been measured in the ground states of each isotopic species. From a least-square adjustment to fit 12 rotational constants, the following structural parameters were obtained:r(P−F)=1.582 ± 0.003 A;r(P=S)=1.902 ± 0.001 A;r(P-C)=1.800 ± 0.001 A;r(C-H)=1.088 ± 0.002 A; ∢HCP=109.28 ± 0.12°; ∢SPF=114.50 ± 0.13°; and SPC=116.33 ± 0.06°. From Stark effect measurements, the dipole moment components have been determined to be ¦μ a ¦ =3.556 ± 0.005; ¦μ c ¦=2.026 ± 0.009; and ¦μ t ¦=4.093 ± 0.009 (D). The Raman spectra (3200 to 100 cm−1) of each isotopic species have been measured for the solid, and liquid and qualitative depolarization values obtained. Additionally, the mid-infrared spectra (3200 to 500 cm−1) of the solids have been recorded. Proposed assignments of the normal modes have been made on the basis of Raman depolarization values and group frequencies which are supported by normal coordinate analysis utilizing an ab initio force field. Optimized structural parameters have been obtained with both the 3-21G* and 6-31G* basis sets. These results are compared to the corresponding quantities for several similar molecules.