Tantalum pentafluoride
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| Names | |
|---|---|
| Other names
tantalum pentafluoride
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| Identifiers | |
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3D model (JSmol)
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| ECHA InfoCard | 100.029.111 |
| EC Number | 232-022-3 |
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PubChem CID
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| RTECS number | WW5775000 |
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| Properties | |
| TaF5 | |
| Molar mass | 275.95 g/mol |
| Appearance | white powder |
| Density | 4.74 g/cm3, solid |
| Melting point | 96.8 °C (206.2 °F; 369.9 K) |
| Boiling point | 229.5 °C (445.1 °F; 502.6 K) |
| decomposes | |
| +795.0·10−6 cm3/mol | |
| Structure | |
| 0 D | |
| Hazards | |
| Main hazards | HF source |
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EU classification (DSD) (outdated)
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not listed |
| R-phrases (outdated) | 34 |
| S-phrases (outdated) | 26-27-28-36/37/39-45 |
| Flash point | Non-flammable |
| Related compounds | |
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Related compounds
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TaCl5 NbCl5 WF6 |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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 (what is   ?) |
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| Infobox references | |
Tantalum(V) fluoride is the inorganic compound with the formula TaF5. It is one of the principal molecular compounds of tantalum. Characteristic of some other pentafluorides, the compound is volatile but exists as an oligomer in the solid state.
It is prepared by treating tantalum metal with fluorine 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 D3hsymmetry.
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 [TaF
6]−
, [TaF
7]2−
, and [TaF
8]3−
. With neutral Lewis bases, such as diethyl ether TaF5 forms adducts.
TaF
5 is used in combination with HF as a catalyst for the alkylation of alkanes and alkenes and for the protonation of aromatic compounds. The TaF
5–HF system is stable in reducing environments, unlike SbF
5–HF. In the presence of fluoride, tantalum pentafluoride forms the anions [TaF
8]3−
, [TaF
7]2−
, or [TaF
6]−
, 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−
2:
...
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