ELECTROCHEMICAL STUDY OF THE LIGAND SUBSTITUTION-REACTIONS IN OXYFLUORIDE BORON-CONTAINING MELTS

Substitution of ligands during titration with oxides of a molten tripl e eutectic of fluorides of lithium, sodium, and potassium (FLINAK) con taining potassium tetrafluoroborate is studied by linear voltammetry. At the molar ratio O : B = 1, complexes BF4- that are characteristic f or an oxygen-free melt transform into BOF2-. A further increase in the O : B ratio to 2 leads to formation of the BO2- berate complexes. The data obtained are used to elucidate the reason for the different elec trochemical behavior of two berate types (NaBO2 and Na2B4O7) in fluori de melts. In the presence of dissolved NaBO2, only the BO2- berate com plexes exist in the melt. In the presence of Na2B4O7, the oxyfluoride BOF2- and berate BO2- aggregates coexist.