Oxyfluorides oxygen compounds

Bismuth pentafluoride is an active fluorinating agent. It reacts explosively with water to form ozone, oxygen difluoride, and a voluminous chocolate-brown precipitate, possibly a hydrated bismuth(V) oxyfluoride. A similar brown precipitate is observed when the white soHd compound bismuth oxytrifluoride [66172-91 -6] BiOF, is hydrolyzed. Upon standing, the chocolate-brown precipitate slowly undergoes reduction to yield a white bismuth(Ill) compound. At room temperature BiF reacts vigorously with iodine or sulfur above 50°C it converts paraffin oil to fluorocarbons at 150°C it fluorinates uranium tetrafluoride to uranium pentafluoride and at 180°C it converts Br2 to bromine trifluoride, BrF, and bromine pentafluoride, BrF, and chlorine to chlorine fluoride, GIF. It apparently does not react with dry oxygen. 

Oxygen and fluorine ions have very similar ionic radii. This steric similarity ensures relatively easy substitution of the oxygen in the compounds, by fluorine ions. Such substitution opens up huge possibilities for the synthesis of oxyfluoride compounds with desired crystal structure and properties. 

One of the most important parameters that defines the structure and stability of inorganic crystals is their stoichiometry - the quantitative relationship between the anions and the cations [134]. Oxygen and fluorine ions, O2 and F, have very similar ionic radii of 1.36 and 1.33 A, respectively. The steric similarity enables isomorphic substitution of oxygen and fluorine ions in the anionic sub-lattice as well as the combination of complex fluoride, oxyfluoride and some oxide compounds in the same system. On the other hand, tantalum or niobium, which are the central atoms in the fluoride and oxyfluoride complexes, have identical ionic radii equal to 0.66 A. Several other cations of transition metals are also sterically similar or even identical to tantalum and niobium, which allows for certain isomorphic substitutions in the cation sublattice. 

Sharing of an oxygen atom by two central atoms in compounds with chain-type structures weakens the binary Nb=0 bond compared to the corresponding bond in pure isolated ions such as NbOF52 This phenomenon affects the vibration spectra and increases wave numbers of NbO vibrations in the case of isolated oxyfluoride complex ions. Table 31 displays IR absorption spectra of some chain- type compounds. Raman spectra are discussed in [212],... 

The steric similarity of oxygen and fluorine ions enables the formation of coordination-type structures in some tantalum and niobium oxyfluoride compounds. 

Decomposition processes of oxyfluorides, in which two compounds are formed, one with a higher oxygen content than the precursor and the other with a lower oxygen content, seem to be common among oxyfluoroniobates. In general, this reaction can be represented as follows ... 

Edmond Fremy, who had watched Louyet perform some of his experiments (33), tried to decompose anhydrous calcium fluoride electro-lytically, and did obtain calcium at die cathode, while a gas, which must have been fluorine, escaped at the anode (34). However, because of its tendency to add on to other substances and form ternary and quaternary compounds, Fremy failed in all his attempts to collect and identify the gas. When he allowed chlorine to act on a fluoride, he obtained no fluorine, but only a fluochloride when he used oxygen in place of chlorine, he obtained an oxyfluoride. 

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