Tantalum fluoride is the inorganic compound

Inorganic compound

Inorganic compounds have traditionally been considered to be of inanimate, non-biological origin. In contrast, organic compounds have an explicit biological origin. However, over the past century, the classification of inorganic vs organic compounds has become less important to scientists,...

 with the formula TaF₅. It is one of the principal molecular compounds of tantalum

Tantalum

Tantalum is a chemical element with the symbol Ta and atomic number 73. Previously known as tantalium, the name comes from Tantalus, a character in Greek mythology. Tantalum is a rare, hard, blue-gray, lustrous transition metal that is highly corrosion resistant. It is part of the refractory...

. Characteristic of some other pentafluorides, the compound is volatile but exists as an oligomer in the solid state.

Preparation and structure

It is prepared by treating tantalum metal with fluorine

Fluorine

Fluorine is the chemical element with atomic number 9, represented by the symbol F. It is the lightest element of the halogen column of the periodic table and has a single stable isotope, fluorine-19. At standard pressure and temperature, fluorine is a pale yellow gas composed of diatomic...

 gas. NbF₅ is prepared similarly.

Solid and molten TaF₅ is tetrameric, consisting of four TaF₄ centers linked together via bridging fluoride centers. Gaseous TaF₅ adopts the trigonal pyramidal structure with D_3h symmetry

Symmetry group

The symmetry group of an object is the group of all isometries under which it is invariant with composition as the operation...

.

Reactions and derivatives

The tendency of TaF₅ to form clusters in the solid state indicates the Lewis acidity of the monomer. Indeed, TaF₅ reacts with fluoride sources to give the ions , , and . With neutral Lewis bases, such as diethyl ether

Diethyl ether

Diethyl ether, also known as ethyl ether, simply ether, or ethoxyethane, is an organic compound in the ether class with the formula . It is a colorless, highly volatile flammable liquid with a characteristic odor...

 TaF₅ forms adduct

Adduct

An adduct is a product of a direct addition of two or more distinct molecules, resulting in a single reaction product containing all atoms of all components. The resultant is considered a distinct molecular species...

s.

is used in combination with HF

Hydrogen fluoride

Hydrogen fluoride is a chemical compound with the formula HF. This colorless gas is the principal industrial source of fluorine, often in the aqueous form as hydrofluoric acid, and thus is the precursor to many important compounds including pharmaceuticals and polymers . HF is widely used in the...

 as a catalyst for the alkylation

Alkylation

Alkylation is the transfer of an alkyl group from one molecule to another. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion or a carbene . Alkylating agents are widely used in chemistry because the alkyl group is probably the most common group encountered in...

 of alkane

Alkane

Alkanes are chemical compounds that consist only of hydrogen and carbon atoms and are bonded exclusively by single bonds without any cycles...

s and alkene

Alkene

In organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond...

s and for the protonation

Protonation

In chemistry, protonation is the addition of a proton to an atom, molecule, or ion. Some classic examples include*the protonation of water by sulfuric acid:*the protonation of isobutene in the formation of a carbocation:2C=CH2 + HBF4 → 3C+ + BF4−*the protonation of ammonia in the...

 of aromatic

Aromaticity

In organic chemistry, Aromaticity is a chemical property in which a conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibit a stabilization stronger than would be expected by the stabilization of conjugation alone. The earliest use of the term was in an article by August...

 compounds. The system is stable in reducing environments, unlike

Fluoroantimonic acid

Fluoroantimonic acid is a mixture of hydrogen fluoride and antimony pentafluoride in various ratios. The 1:1 combination forms the strongest known superacid, which has been demonstrated to protonate even hydrocarbons to afford carbocations and H2....

. In the presence of fluoride, tantalum pentafluoride forms the anions or , depending on the nature of the counterion and the concentration of HF. High concentrations of HF favor the hexafluoride by virtue of the formation of :

+ HF +

In the Marignac

Jean Charles Galissard de Marignac

Jean Charles Galissard de Marignac was a Swiss chemist whose work with atomic weights suggested the possibility of isotopes and the packing fraction of nuclei and whose study of the rare earth elements led to his discovery of ytterbium in 1878 and codiscovery of gadolinium in 1880.- Life and work...

 process, Nb and Ta are separated by fractional crystallization of K₂TaF₇

Potassium heptafluorotantalate

Potassium heptafluorotantalate is an inorganic compound with the formula K2TaF7. This white, water-soluble solid is an intermediate in the purification of tantalum from its ores and is the precursor to the metal.-Structure:...

from solutions of hydrofluoric acid. Under these conditions, niobium forms K₂NbOF₅, which is more soluble than K₂TaF₇]]. Reduction of K₂TaF₇ with sodium gives metallic Ta.