LOW-TEMPERATURE FLUORINATION OF RUTHENIUM AND OSMIUM DI-OXIDES AND TETRA-OXIDES

The fluorination of ruthenium dioxide, RuO2, and osmium di- and tetra- oxides, OsO2 and OsO4, has been studied at ambient temperature using f luorinating agents of variable strength such as chlorine trifluoride C lF3, bromine pentafluoride BrF5 or krypton difluoride KrF2. The result s of this study and those previously obtained on the fluorination of r uthenium and osmium tetroxides (RuO4, OsO4) are compared and discussed . The reaction of RuO2 with KrF2 in HF solution leads to the ruthenium (V) dioxygenyl salt, O2 RuF6-, and that of OSO2 to osmium oxide pentaf luoride, OsOF5. This oxide fluoride also results from the reaction of OSO2 or OsO4 with liquid ClF3. However, osmium trioxide difluoride, OS O3F2, and small quantities of osmium dioxide tetrafluoride, OSO2F4, ar e formed at intermediate stages of the fluorination of OSO4 by ClF3. A slow reaction takes place between liquid BrF5 and OSO4 to yield OSO3F 2 as the sole osmium derivative. A large excess of KrF, or its derivat ive cation KrF+ in HF solution leaves OsOF5 unreacted. In contrast to the strength of the metal-oxygen bonds generally observed for the oxid e fluorides of osmium in high oxidation states, the weakness of the co rresponding Ru-O bonds is the rule. The differences between the fluori nation pathways of the oxides of ruthenium and those of osmium are thu s explained.