Tetrafluoroborate

Disadvantages to BF−4 include its slight sensitivity to hydrolysis and decomposition via loss of a fluoride ligand, whereas ClO−4 does not suffer from these problems.

With a formula weight of 86.8, BF–4 is also conveniently the smallest weakly coordinating anion from the point of view of equivalent weight, often making it the anion of choice for preparing cationic reagents or catalysts for use in synthesis, in the absence of other substantial differences in chemical or physical factors.

Despite the low reactivity of the tetrafluoroborate anion in general, BF−4 serves as a fluorine source to deliver an equivalent of fluoride.

Fluoroborates of alkali metals and ammonium ions crystallize as water-soluble hydrates with the exception of potassium, rubidium, and cesium.

Some examples include: An electrochemical cycle involving ferrous/ferric tetrafluoroborate is being used to replace thermal smelting of lead sulfide ores by the Doe Run Company.