Tantalum(V) chloride

Chemical compound From Wikipedia, the free encyclopedia

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]

Quick facts Names, Identifiers ...
Tantalum(V) chloride
  Tantalum, Ta;   Chlorine, Cl
Names
IUPAC names
Tantalum(V) chloride
Tantalum pentachloride
Identifiers
  • 7721-01-9 TaCl5 checkY
  • 17499-29-5 Ta2Cl10 X markN
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.028.869 Edit this at Wikidata
EC Number
  • 231-755-6
UNII
  • Key: OEIMLTQPLAGXMX-UHFFFAOYSA-I
  • InChI=1S/5ClH.Ta/h5*1H;/q;;;;;+5/p-5
  • monomer: Cl[Ta](Cl)(Cl)(Cl)Cl
  • dimer: Cl[Ta-]1(Cl)(Cl)(Cl)[Cl+][Ta-]([Cl+]1)(Cl)(Cl)(Cl)Cl
Properties
TaCl5
Molar mass 358.213 g/mol
Appearance white monoclinic crystals[1][page needed][contradictory]
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)
reacts
Solubility chloroform, CCl4
+140.0×10−6 cm3/mol
Structure
Monoclinic, mS72
C2/m, No. 12
Thermochemistry
221.75 J K−1 mol−1
−858.98 kJ/mol
Hazards
GHS labelling:
GHS05: CorrosiveGHS07: Exclamation mark
Danger
H302, H314, H335
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 diamondHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
3
0
0
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
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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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][page needed]

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

Further reading

External links

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