The Molecular Structure of MoF6, WF6, and UF6 from Infrared and Raman Spectra

This paper is a report of the complete investigation and interpretation of the Raman and infrared spectra of MoF6, WF6, and UF6. The Raman photographs of MoF6 and WF6 exhibit three intense lines in accord with earlier measurements on UF6 in solution. The exploration of the infrared spectra of MoF6 and WF6 from 2–40μ yielded a great many bands for each molecule. Two of these were quite intense in each case and were identified as fundamentals while the remaining weaker ones were identified as overtones and combinations. The infrared spectrum of UF6 was repeated from 2–17μ with substantially the same results as in the earlier work. Extension of this spectrum from 17–40μ was made and three new bands were discovered. Because of the great similarity of the spectra of these three molecules, an interpretation of the bands was made along lines suggested by Bigeleisen, Mayer, Stevenson, and Turkevich for UF6, that the molecule belongs to the point group Oh and has totally symmetric octahedral structure. It was possible to fit all but five very weak bands into an identification scheme based on this model. The success of this effort is taken to be conclusive evidence in favor of the Oh type symmetry.