Tantalum(V) chloride

Tantalum(V) chloride
  Tantalum, Ta;   Chlorine, Cl
Names
IUPAC names
Tantalum(V) chloride
Tantalum pentachloride
Identifiers
CAS Number
  • 7721-01-9 TaCl5 checkY
  • 17499-29-5 Ta2Cl10 ☒N
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.028.869
EC Number
  • 231-755-6
PubChem CID
UNII
CompTox Dashboard (EPA)
InChI
  • Key: OEIMLTQPLAGXMX-UHFFFAOYSA-I
  • InChI=1S/5ClH.Ta/h5*1H;/q;;;;;+5/p-5
SMILES
  • monomer: Cl[Ta](Cl)(Cl)(Cl)Cl
  • dimer: Cl[Ta-]1(Cl)(Cl)(Cl)[Cl+][Ta-]([Cl+]1)(Cl)(Cl)(Cl)Cl
Properties
Chemical formula
 TaCl5
Molar mass 358.213 g/mol
Appearance white monoclinic crystals[1]
Density 3.68 g/cm3
Melting point 216 °C (421 °F; 489 K)
Boiling point 239.4 °C (462.9 °F; 512.5 K) (decomposes)
Solubility in water
 reacts
Solubility chloroform, CCl4
Magnetic susceptibility (χ)
 +140.0×10−6 cm3/mol
Structure
Crystal structure
 Monoclinic, mS72
Space group
 C2/m, No. 12
Thermochemistry
Std molar
entropy (S⦵298)
 221.75 J K−1 mol−1
Std enthalpy of
formation (ΔfH⦵298)
 −858.98 kJ/mol
Hazards
GHS labelling:
Pictograms
 GHS05: CorrosiveGHS07: Exclamation mark
Signal word
 Danger
Hazard statements
 H302, H314, H335
Precautionary statements
 P260, P264+P265, P270, P271, P280, P301+P317, P301+P330+P331, P302+P361+P354, P304+P340, P305+P351+P338, P305+P354+P338, P310, P316, P330, P363, P403+P233, P405, P501
NFPA 704 (fire diamond)
NFPA 704 four-colored diamond
3
0
0
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
LD50 (median dose)
 1900 mg/kg (oral, rat)
Safety data sheet (SDS) External SDS
Related compounds
Other anions
Other cations
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Tantalum(V) chloride, also known as tantalum pentachloride, is an inorganic compound with the formula TaCl5. It takes the form of a white powder, which is highly sensitive to moisture. It is synthesised and manipulated under anhydrous conditions, using air-free techniques.[2][3]

Structure

TaCl5 crystallizes in the monoclinic space group C2/m.[4] 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 Ta2Cl10 is retained in non-complexing solvents and to a large extent in the molten state. In the vapour state, however, TaCl5 is monomeric. This monomer adopts a trigonal bipyramidal structure, like that of PCl5.[5]

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.[6]

2 Ta + 5 Cl2 → 2 TaCl5
2 Ta + 10 HCl → 2 TaCl5 + 5 H2

It can also be prepared by a reaction between tantalum pentoxide and thionyl chloride at 240 °C.[3]

Ta2O5 + 5 SOCl2 → 2 TaCl5 + 5 SO2

Tantalum pentachloride is commercially available, however samples can be contaminated with tantalum(V) oxytrichloride (TaOCl3), formed by hydrolysis. Samples contaminated with niobium pentachloride appear yellow.[3]

Reactions

TaCl5 is electrophilic. It forms adducts with a variety of Lewis bases. It serves as a Lewis acid in Friedel-Crafts reactions.[7]

Simple adducts

TaCl5 forms stable complexes with ethers:.[7][8]

TaCl5 + R2O → TaCl5(OR2) (R = Me, Et)

TaCl5 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:[9]

TaCl5 + PCl5 → [PCl4]+[TaCl6]−
TaCl5 + OPCl3 → [TaCl5(OPCl3)]

Tantalum pentachloride reacts with tertiary amines to give adducts:[7]

TaCl5 + 2 R3N → [TaCl5(NR3)]

Chloride displacement reactions

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

TaCl5 + 3 OPPh3 → [TaOCl3(OPPh3)]x ...

Anhydrous TaCl5 (Ta2Cl10) rapidly (but not violently) hydrolyses in water at room temperature.[10]

Tantalum pentachloride reacts with sodium ethoxide to give the pentaethoxide, which also exists as a dimer:[11]

5 NaOC2H5 + TaCl5 → Ta(OC2H5)5 + NaCl

A variety of related alkoxides and mixed chloro-alkoxides are known, e.g. Ta(OCH3)5 and Ta(OCH2CH3)3Cl2.[7]

Ammonium chloride gives the nitrido complex [TaCl5N]3−.[12]

Reduction

Reduction of tantalum(V) chloride gives anionic and neutral clusters including [Ta6Cl18]4− and [Ta6Cl14](H2O)4.[13]

References

  1. ^ Lide, David R., ed. (2006). CRC Handbook of Chemistry and Physics (87th ed.). Boca Raton, Florida: CRC Press. ISBN 0-8493-0487-3.
  2. ^ Clark, R. J. H.; Brown, D.; Bailar, J. C.; Emeléus, H. J.; Nyholm, Ronald (2013). The Chemistry of Vanadium, Niobium and Tantalum: Pergamon Texts in Inorganic Chemistry. Texts in Inorganic Chemistry (1. Aufl ed.). s.l.: Elsevier Reference Monographs. ISBN 978-1-4831-8170-7.
  3. ^ a b c G. Brauer (1963). "Niobium (V) and Tantalum (V) Chlorides". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry, 2nd Ed. Vol. 2. NY, NY: Academic Press. pp. 1302–1305.
  4. ^ Rabe, Susanne; Müller, Ulrich (2000). "Crystal structure of tantalum pentachloride, (TaCl5)2". Z. Kristallogr. - New Cryst. Struct. 215 (1): 1–2. Bibcode:2000ZK....215....1R. doi:10.1515/ncrs-2000-0102.
  5. ^ Fairbrother, F. (1967). The Chemistry of Niobium and Tantalum. Elsevier.
  6. ^ Young, Ralph C.; Brubaker, Carl H. (1952). "Reaction of Tantalum with Hydrogen Chloride, Hydrogen Bromide and Tantalum Pentachloride; Action of Hydrogen on Tantalum Pentachloride". Journal of the American Chemical Society. 74 (19): 4967. Bibcode:1952JAChS..74.4967Y. doi:10.1021/ja01139a524.
  7. ^ a b c d Hubert-Pfalzgraf, Liliane G. (2005). "Niobium & Tantalum: Inorganic & Coordination Chemistry". Encyclopedia of Inorganic Chemistry. doi:10.1002/0470862106.ia153. ISBN 978-0-470-86078-6.
  8. ^ Cowley, A.; Fairbrother, F.; Scott, N. (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.: 3133–3137. doi:10.1039/JR9580003133.
  9. ^ Bullock, J. I.; Parrett, F. W.; Taylor, N. J. (1973). "Some Metal Halide–Phosphorus Halide–Alkyl Halide Complexes. Part II. Reactions with Niobium and Tantalum Pentachlorides and Tungsten Hexachloride". J. Chem. Soc., Dalton Trans. (5): 522–524. doi:10.1039/DT9730000522.
  10. ^ "Tantalum(V) chloride | Tantalum pentachloride | TaCl5". Ereztech. Retrieved 2025-12-03.
  11. ^ Schubert, U. (2003). "Sol–Gel Processing of Metal Compounds". In McCleverty, J. A.; Meyer, T. J. (eds.). Comprehensive Coordination Chemistry II. Reference Module in Chemistry, Molecular Sciences and Chemical Engineering. Vol. 7. Pergamon. pp. 629–656. doi:10.1016/B0-08-043748-6/06213-7. ISBN 978-0-12-409547-2.
  12. ^ Berg, Rolf W. (1992). "Progress in Niobium and Tantalum Coordination Chemistry". Coordination Chemistry Reviews. 113: 1–130. doi:10.1016/0010-8545(92)80074-2.
  13. ^ Duraisamy, Thirumalai; Hay, Daniel N. T.; Messerle, Louis (2014). "Octahedral Hexatantalum Halide Clusters". Inorganic Syntheses. Vol. 36. pp. 1–8. doi:10.1002/9781118744994.ch1. ISBN 9781118744994.

Further reading

  • Ozin, G. A.; Walton, R. A. (1970). "Vibrational Spectra and Structures of the 1:1 Complexes of Niobium and Tantalum, Pentachlorides and Tantalum Pentabromide with Aceto-, Perdeuterioaceto-, and Propionitriles in the Solid and Solution States and a Vibrational Analysis of the Species MX5, NC·CY3 (Y = H or D)". J. Chem. Soc. A: 2236–2239. doi:10.1039/j19700002236.
  • Đorđević, C.; Katović, V. (1970). "Co-ordination Complexes of Niobium and Tantalum. Part VIII. Complexes of Niobium(IV), Niobium(V), and Tantalum(V) with Mixed Oxo, Halogeno, Alkoxy, and 2,2′-Bipyridyl Ligands". J. Chem. Soc. A: 3382–3386. doi:10.1039/j19700003382.
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