BrF3 Bromine fluoride

The actual composition present in the Br2/BrF3 mixture is not known, and any fluorination reaction may be a composite reaction of BrF, BrF3 and BrF5. It is not necessary to assume that BrFa is the reactive constituent, although this is probable. Consider the fluorination of a species X—a metal, oxide, oxysalt, halide, etc.—to the fluoride XF by a mixture of bromine fluorides BrFgj. The general reaction is... 

Bil3 Bismuth(III) iodide, 4 114 2Bi(N03)3-3Mg(N03)2-24H20 Bismuth magnesium nitrate, 2 57 BrF Bromine (I) fluoride, 3 185 BrF3 Bromine(III) fluoride, 3 184 BrF5 Bromine (V) fluoride, 3 185 BrH Hydrobromic acid, 1 151, 152, 155... 

Another anhydrous solvent that is frequently used for the synthesis of tantalum and niobium fluoride compounds is bromine trifluoride, BrF3. At ambient temperature, bromine trifluoride is light yellow liquid characterized by a boiling point of 126°C, a melting point of 9°C and a density of 2.84 g/cm3 at melting temperature. 

Fluorine and bromine.—While no sensible reaction between fluorine and chlorine has been observed, H. Moissan found that fluorine unites violently with cold bromine vapour, and the reaction is attended by une jiamme eclair ante, but with the evolution of little heat. P. Lebeau found that no flame is produced if dry liquid bromine is employed, and he showed that the product of the reaction is bromine trifluoride BF3, a result almost simultaneously established by E. B. E. Prideaux. No reaction —solvent or chemical—occurs between liquid fluorine and solid bromine, and the fluorine can be distilled from the latter without any sign of interaction. There is no indication of the formation of a lower bromide, say, BrF and attempts to prepare a higher fluoride, say BrF4, by passing a large excess of fluorine over the trifluoride, were fruitless. Bromine trifluoride was also made by the action of fluorine on potassium bromide KBr-[-2F2=KF+BrF3. 

Halide donor-acceptor reactions (of XX ) are generally those in which X is donated to or accepted from an interhalogen. They include self-ionization reactions such as that of BrF3 shown in Equation (18.53). This property makes bromine trifluoride a common aprotic (without protons) self-ionizing solvent. In addition to its self-ionization, BrF3 readily accepts fluoride ions from other sources, such as alkali-metal fluorides, to produce salts containing the bromine tetrafluoride ion, as shown in Equation (18.54). Conversely, it can donate fluoride ions to produce salts containing the bromine difluoride cation, as shown in Equation (18.55). 

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