Chapter 5 - Syntheses and Structures of the Oxide Fluorides of the Main-Group and Transition Metal Elements

Abstract

This chapter summarizes the syntheses and structural findings related to the oxide fluorides that have been synthesized during the period 1985-1998. The replacement of fluorine atoms with oxygen atoms generally leads to the stabilization of higher oxidation states, and the stabilization is further enhanced when the high-valent oxide fluoride occurs as an anion. This is illustrated by the stabilization of the highest oxidation state in the periodic table, +8. The tetroxides, RuO4, OsO4 and explosive XeO4 are all known as well as a host of notoriously stable perxenates, XeO64-. While RuVlll oxide fluorides are unknown, OsO2F4 and OsO3F2 are stable compounds and XeO3F2 and XeO2F4 have been prepared in small quantities from XeO4. In contrast, the highest oxidation state that can be attained in the binary fluorides of these elements is +6, for example XeF6, RuF6, and OsF6. Direct solid state reactions have been used to prepare two new InIII oxide fluorides: Ba2InO3F and Ba3In2OsF2. The Ba2InO3F structure has ordered anions producing a K2NiF4 superstructure with alternating layers of oxide and fluoride ions. The Ba3In2OsF2 structure also shows ordering of the oxide and fluoride ions, producing sheets of vertex-sharing indium-oxygen square pyramids separated by BaF layers. The electrosynthesis of the known compound, T1OF, has been reported from aqueous HF/T1F and T1OH/T1F solutions.