Tetrafluoroborate is the anion BF4−. This tetrahedral species is isoelectronic with tetrafluoromethane, CF4 and tetrafluoroammonium NF4+, and is valence isoelectronic with many stable and important species including the closely related anion perchlorate, ClO4−. It arises by the reaction of fluoride salts with the Lewis acid BF3, treatment of tetrafluoroboric acid with base, or by treatment of boric acid with hydrofluoric acid.
Read more about Tetrafluoroborate: BF4− As An Anion in Inorganic and Organic Chemistry, Examples of BF4− Salts