Molecular Structures of PCl4F, PCl3F2, PCl2F3, and PF5: Infrared and Low-Temperature Raman Vibrational Spectra

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Abstract
Molecular structures of PCl4F, PCl3F2, PCl2F3, and PF5 are derived from vapor‐state infrared spectra (2000–250 cm—1) and low‐temperature liquid‐state Raman displacements (Δν=50–1200 cm—1) together with qualitative polarization measurements. All of the compounds appear to have a basic trigonal bipyramidal framework. The spectra of PCl4F are best interpreted in terms of a C3v structure in which the fluorine atom occupies an axial site; in PCl3F2 (D3h point group) the fluorine atoms also assume axial positions. For PCl2F3, the symmetrical D3h structure is shown to be incorrect. Available evidence supports the C2v structure in which the fluorine atoms appear in one equatorial and two axial sites. Phosphorus pentafluoride is found to have a regular trigonal bipyramidal structure. Complete vibrational assignments are made in terms of the normal modes and thermodynamic functions are evaluated for PCl5, PCl3F2, and PF5.