Tetrafluoroborate

Tetrafluoroborate is the anion BF⁻
₄. This tetrahedral species is isoelectronic with tetrafluoroberyllate (BeF²⁻
₄), tetrafluoromethane (CF₄), and tetrafluoroammonium (NF⁺
₄) and is valence isoelectronic with many stable and important species including the perchlorate anion, ClO⁻
₄, which is used in similar ways in the laboratory. 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.