LASER RAMAN SPECTROSCOPIC INVESTIGATIONS OF SOME FLUOROXENON COMPOUNDS

Abstract

<p>The Raman spectra of a number of salts of fluoro- and oxy-fluoro cations of xenon compounds, in a variety of oxidation states are reported. The preparation of some of these compounds is reported for the first time. Characteristic frequencies along with comprehensive assignments are given for the Xe₂F₃⁺, XeF⁺, XeF₃, XeOF₃⁺, Xe₂OF⁺, XeF₅⁺ and Xe₂F₁₁⁺ cations, and some other related compounds both in the solid state and in HF solution. Reactions of XeF₂ with BF₃ have been shown to give the new BF₄⁻ salts, XeF⁺BF₄⁻ and Xe₂F₃⁺BF₄⁻, while the reaction of XeF₄ with AsF₅ has been shown to give the new salt XeF₃⁺As₂F₁₁⁻⁻. Largely, by the aid of Raman spectroscopy, the molecular geometries of these cations are shown to be in accord with electron pair repulsion theory.</p> <p>Direct spectroscopic evidence is presented for the first time for the presence of weak covalent interaction, i.e., fluorine bridges, in a number of the salts studied. With the aid of the available X-ray crystallographic data, and the vibrational data presented, it was found that fluorine bridge interactions increase in strength in the series XeF₅⁺ < XeF₃⁺ < XeF⁺. Thus, in contrast to the previously supposed order the fluoride ion donating ability of the fluorides was found to decrease, in the order XeF₆ > XeF₄ > XeF₂.</p> <p>A useful correlation has been found between the xenon-fluorine stretching frequencies and the bond lengths. This correlation has been found to hold for a wide variety of fluorocations, and neutral molecules, in a number of different oxidation states and for a wide range of Xe-F bond lengths, including the Xe---F bridge bonds.</p>