Tantalum(V) chloride

Structure

crystallizes in the monoclinic space group C2/m. The ten chlorine atoms define a pair of octahedra that share a common edge. The tantalum atoms occupy the centres of the octahedra and are joined by two chlorine bridging ligands. The dimeric structure is retained in non-complexing solvents and to a large extent in the molten state. In the vapour state, however, is monomeric. This monomer adopts a trigonal bipyramidal structure, like that of .

Synthesis

Tantalum pentachloride can be prepared by treating powdered metallic tantalum with chlorine gas at between 170 and 250 °C. This reaction can also be performed using HCl at 400 °C.

: :

It can also be prepared by a reaction between tantalum pentoxide and thionyl chloride at 240 °C.

:

Tantalum pentachloride is commercially available, however samples can be contaminated with tantalum(V) oxytrichloride (), formed by hydrolysis. Samples contaminated with niobium pentachloride appear yellow.

Reactions

is electrophilic. It forms adducts with a variety of Lewis bases. It serves as a Lewis acid in Friedel-Crafts reactions.

Simple adducts

forms stable complexes with ethers:. : (R = Me, Et)

also reacts with phosphorus pentachloride and phosphoryl chloride, the former as a chloride donor and the latter serves as a ligand, binding through the oxygen: : :

Tantalum pentachloride reacts with tertiary amines to give adducts: :

Chloride displacement reactions

Tantalum pentachloride reacts at room temperature with an excess of triphenylphosphine oxide to give oxychlorides: : ...

Hydrolysis, alcoholysis, ammonolysis and related reactions

Anhydrous TaCl5 (Ta2Cl10) rapidly (but not violently) hydrolyses in water at room temperature.

Tantalum pentachloride reacts with sodium ethoxide to give the pentaethoxide, which also exists as a dimer: : A variety of related alkoxides and mixed chloro-alkoxides are known, e.g. .

Ammonium chloride gives the nitrido complex .

Reduction

Reduction of tantalum(V) chloride gives anionic and neutral clusters including and .

References

References

1. {{RubberBible87th{{page needed. (May 2025)
2. Clark, R. J. H.. (2013). "The Chemistry of Vanadium, Niobium and Tantalum: Pergamon Texts in Inorganic Chemistry". Elsevier Reference Monographs.
3. G. Brauer. (1963). "Handbook of Preparative Inorganic Chemistry, 2nd Ed.". Academic Press.
4. (2000). "Crystal structure of tantalum pentachloride, (TaCl₅)₂". [[Z. Kristallogr. - New Cryst. Struct.]].
5. Fairbrother, F.. (May 2025). "The Chemistry of Niobium and Tantalum". Elsevier.
6. (1952). "Reaction of Tantalum with Hydrogen Chloride, Hydrogen Bromide and Tantalum Pentachloride; Action of Hydrogen on Tantalum Pentachloride". [[Journal of the American Chemical Society]].
7. (2005). "Encyclopedia of Inorganic Chemistry".
8. (1958). "The Halides of Niobium (Columbium) and Tantalum. Part V. Diethyl Ether Complexes of the Pentachlorides and Pentabromides; the Solubility of Tantalum Pentaiodide in Ether". [[J. Chem. Soc.]].
9. "Tantalum(V) chloride {{!}} Tantalum pentachloride {{!}} TaCl5".
10. Schubert, U.. (2003). "Comprehensive Coordination Chemistry II". [[Pergamon]].
11. (1992). "Progress in Niobium and Tantalum Coordination Chemistry". Coordination Chemistry Reviews.
12. (May 2025). "Inorganic Syntheses".