Description
Sodium tetrafluoroborate is an organic compound that has the molecular formula NaBF4. The compound is a salt that forms white or colorless water-soluble rhombic crystals. It is less soluble in organic solvents and readily soluble in water.
Preparation
Sodium tetrafluoroborate can be prepared by reacting tetrafluoroboric with sodium carbonate or hydroxide.
NaOH + HBF4 → NaBF4 + H2O
Na2CO3 + 2 HBF4 → 2 NaBF4 + H2O + CO2
Applications
Sodium tetrafluoroborate can be used as a catalyst for the synthesis of bis(indolyl)methanes via electrophilic substitution reaction of indoles with ketones and aldehydes. In the synthesis of ionic liquids such as trihexyl(tetradecyl)phosphonium tetrafluoroborat and 1-butyl-3-methylimidazolium tetrafluoroborate.
In the laboratory, sodium tetrafluoroborate may be used for the synthesis of boron fluoride. It may also be used in the synthesis of fluoroheterocyclic and fluoro-nucleic acids. The compound is also used in metal finishing, fluxes, and plating circuits.
Chemical Properties
white crystals or powder, crystallizes in the
anhydrous form as clear, orthogonal, stubby prisms. Anhydrous
NaBF4 does not etch glass. Readily soluble in water. Rhombic
crystals, isodimorphous with NaClO4.
Uses
Fluorinating agent, see Lawton, Levy, J. Am. Chem. Soc. 77, 6083 (1955).
Uses
Sodium Tetrafluoroborate is used in various metal finishing and plating circuits.
Uses
Sodium tetrafluoroborate may be used for the laboratory synthesis of boron fluoride. It may be used for the synthesis of fluoro-nucleic acids and fluoroheterocyclic compounds.
General Description
Sodium tetrafluoroborate (NaBF
4) is colorless sodium salt and its crystals belong to the rhombic crystal system. It can be synthesized by reacting tetrafluoroboric acid with sodium carbonate or hydroxide.
Flammability and Explosibility
Not classified
Safety Profile
Moderately toxic by subcutaneous route. When heated to decomposition it emits toxic fumes of Fand Na2O.
Synthesis
Boric acid (6.2 g.) is added, with cooling, to 25 g. of 40% hydrofluoric acid contained in a Pt dish. The mixture is left standing for
six hours at room temperature, then cooled with ice, and 5.3 g of
dry Na2CO3 is added. The solution is then evaporated until crystallization starts. The salt can be recrystallized from water, whereby
large, beautiful single crystals can be obtained. The NaBF4 is
finally dried under vacuum.
2 H3BO3 + 8 HF + Na2CO3 = 2 NaBF4 + 7 H2O + CO2
Purification Methods
Crystallise the fluoroborate from hot water (50mL/g) by cooling to 0o. Alternatively, free it from insoluble material by dissolving it in a minimum amount of water; then fluoride ions are removed by adding concentrated lanthanum nitrate in excess. After removing lanthanum fluoride by centrifugation, the supernatant is passed through a cation-exchange column (Dowex 50, Na+-form) to remove any remaining lanthanum [Anbar & Guttman J Phys Chem 64 1896 1960]. It has also been recrystallised from anhydrous MeOH and dried in a vacuum at 70o for 16hours. Keep it dry as it is hygrosopic. [Delville et al. J Am Chem Soc 109 7293 1987.]
