SPECTRA AND STRUCTURE OF ORGANOPHOSPHORUS COMPOUNDS .49. 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 ((CH 3)2PSF)-S-34 have been investigated from 20.0 to 40.0 GHz. Both a-type R branch and c-type Q branch transitions have been measured in the gr ound states of each isotopic species. From a least-square adjustment t o fit 12 rotational constants, the following structural parameters wer e obtained: r(P-F) = 1.582 +/- 0.003 angstrom; r(P=S) = 1.902 +/- 0.00 1 angstrom; r(P-C) = 1.800 +/- 0.001 angstrom; r(C-H) = 1.088 +/- 0.00 2 angstrom; less than with right parenthesis through it HCP = 109.28 /- 0.12-degrees; less than with right parenthesis through it SPF = 114 .50 +/- 0.13-degrees; and SPC = 116.33 +/- 0.06-degrees. From Stark ef fect measurements, the dipole moment components have been determined t o be \mu(a)\ = 3.556 +/- 0.005; \mu(c)\ = 2.026 +/- 0.009; and \mu(t)\ = 4.093 +/- 0.009 (D). The Raman spectra (3200 to 100 cm-1) of each i sotopic species have been measured for the solid, and liquid and quali tative 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 d epolarization values and group frequencies which are supported by norm al coordinate analysis utilizing an ab initio force field. Optimized s tructural parameters have been obtained with both the 3-21G and 6-31G basis sets. These results are compared to the corresponding quantiti es for several similar molecules.