Tantalum(V) chloride

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Tantalum(V) chloride
IUPAC names
Tantalum(V) chloride
Tantalum pentachloride
3D model (JSmol)
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EC Number
  • 231-755-6
PubChem CID
Molar mass 358.213 g/mol
Appearancewhite 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 chloroform, CCl4
+140.0×10−6 cm3/mol
Monoclinic, mS72
C2/m, No. 12
221.75 J K−1 mol−1
-858.98 kJ/mol
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
1900 mg/kg (oral, rat)
Related compounds
Other anions
Tantalum(V) fluoride
Tantalum(V) bromide
Tantalum(V) iodide
Other cations
Vanadium(IV) chloride
Niobium(V) chloride
Related compounds
Tantalum(III) chloride, Tantalum(IV) chloride
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 and is commonly used as a starting material in tantalum chemistry. It readily hydrolyzes to form tantalum(V) oxychloride (TaOCl3) and eventually tantalum pentoxide (Ta2O5); this requires that it be synthesised and manipulated under anhydrous conditions, using air-free techniques.



TaCl5 crystallizes in the monoclinic space group C2/m. [2] 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, TaCl5 is monomeric. This monomer adopts a trigonal bipyramidal structure, like that of PCl5. [3]

Physical Properties

The solubility of tantalum pentachloride increases slightly for the following series of aromatic hydrocarbons:

benzene < toluene < m-xylene < mesitylene

This is reflected in the deepening of colour of the solutions from pale yellow to orange. Tantalum pentachloride is less soluble in cyclohexane and carbon tetrachloride than in the aromatic hydrocarbons. Such solutions of tantalum pentachloride are also known to be poor conductors of electricity, indicating little ionization. TaCl5 is purified by sublimation to give white needles.


Tantalum pentachloride can be prepared by reacting powdered metallic tantalum with chlorine gas at between 170 and 250 °C. This reaction can also be performed using HCl at 400 °C. [4]

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

Ta2O5 + 5 SOCl2 → 2 TaCl5 + 5 SO2

Tantalum pentachloride is commercially available, however samples can be contaminated with tantalum(V) oxychloride (TaOCl3), formed by hydrolysis.


TaCl5 is electrophilic and it behaves like a Friedel–Crafts catalyst, similar to AlCl3. It forms adducts with a variety of Lewis bases. [5]

Simple adducts

TaCl5 forms stable complexes with ethers:

TaCl5 + R2O → TaCl5(OR2) (R = Me, Et)

TaCl5 also reacts with phosphorus pentachloride and phosphorus oxychloride, the former as a chloride donor and the latter serves as a ligand, binding through the oxygen:

TaCl5 + PCl5 → [PCl+
TaCl5 + OPCl3 → [TaCl5(OPCl3)]

Tantalum pentachloride reacts with tertiary amines to give crystalline adducts.

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 ...

The presumed initial formation of adducts between TaCl5 and hydroxyl compounds such as alcohols, phenols and carboxylic acids is followed immediately by the elimination of hydrogen chloride and the formation of Ta–O bonds:

TaCl5 + 3 HOEt → TaCl2(OEt)3 + 3 HCl

In the presence of ammonia as a HCl acceptor, all five chloride ligands are displaced with formation of Ta(OEt)5. Similarly TaCl5 reacts with lithium methoxide in anhydrous methanol to form related methoxy derivatives:

TaCl5 + 4 LiOMe → Ta(OMe)4Cl + 4 LiCl

Ammonia will displace most of the chloride ligands from TaCl5 to give a cluster. Chloride is displaced more slowly by primary or secondary amines but the replacement of all five chloride centers by amido groups has been achieved by the use of lithium dialkylamides, as illustrated by the synthesis of pentakis(dimethylamido)tantalum:

TaCl5 + 5 LiNMe2 → Ta(NMe2)5

With alcohols, the pentachloride reacts to give alkoxides. As shown for the preparation of tantalum(V) ethoxide, such reactions are often conducted in the presence of base:

10 EtOH + Ta2Cl10 + 10 NH3 → Ta2(OEt)10 + 10 NH4Cl

Tantalum pentachloride is reduced by nitrogen heterocycles such as pyridine.


Reduction of tantalum(V) chloride gives anionic and neutral clusters including [Ta6Cl18]4− and [Ta6Cl14](H2O)4. [6]

Structure of edge-capped octahedral clusters such as Ta6Cl18 . EntryWithCollCode26094.png
Structure of edge-capped octahedral clusters such as Ta6Cl18 .

Related Research Articles

Titanium tetrachloride

Titanium tetrachloride is the inorganic compound with the formula TiCl4. It is an important intermediate in the production of titanium metal and the pigment titanium dioxide. TiCl4 is a volatile liquid. Upon contact with humid air, it forms spectacular opaque clouds of titanium dioxide (TiO2) and hydrated hydrogen chloride. It is sometimes referred to as "tickle" or "tickle 4" due to the phonetic resemblance of its molecular formula (TiCl4) to the word.

Dysprosium(III) chloride

Dysprosium(III) chloride (DyCl3), also known as dysprosium trichloride, is a compound of dysprosium and chlorine. It is a white to yellow solid which rapidly absorbs water on exposure to moist air to form a hexahydrate, DyCl3·6H2O. Simple rapid heating of the hydrate causes partial hydrolysis to an oxychloride, DyOCl.

Phosphorus pentachloride

Phosphorus pentachloride is the chemical compound with the formula PCl5. It is one of the most important phosphorus chlorides, others being PCl3 and POCl3. PCl5 finds use as a chlorinating reagent. It is a colourless, water-sensitive and moisture-sensitive solid, although commercial samples can be yellowish and contaminated with hydrogen chloride.

Phosphorus trichloride

Phosphorus trichloride is a chemical compound of phosphorus and chlorine, having the chemical formula PCl3. It is a toxic and volatile liquid which reacts violently with water to release HCl gas. It has a trigonal pyramidal shape, owing to the lone pairs on the phosphorus. It is an important industrial chemical, being used for the manufacture of phosphites and other organophosphorus compounds for a wide variety of applications. It has a 31P NMR signal at around +220 ppm with reference to a phosphoric acid standard.

Niobium(V) chloride Chemical compound

Niobium(V) chloride, also known as niobium pentachloride, is a yellow crystalline solid. It hydrolyzes in air, and samples are often contaminated with small amounts of NbOCl3. It is often used as a precursor to other compounds of niobium. NbCl5 may be purified by sublimation.

Hafnium tetrachloride

Hafnium(IV) chloride is the inorganic compound with the formula HfCl4. This colourless solid is the precursor to most hafnium organometallic compounds. It has a variety of highly specialized applications, mainly in materials science and as a catalyst.

Phosphoryl chloride

Phosphoryl chloride (commonly called phosphorus oxychloride) is a colourless liquid with the formula POCl3. It hydrolyses in moist air releasing phosphoric acid and fumes of hydrogen chloride. It is manufactured industrially on a large scale from phosphorus trichloride and oxygen or phosphorus pentoxide. It is mainly used to make phosphate esters such as tricresyl phosphate.

Vanadium tetrachloride is the inorganic compound with the formula VCl4. This bright red liquid serves as a useful reagent for the preparation of other vanadium compounds.

Molybdenum(V) chloride

Molybdenum(V) chloride is the inorganic compound with the formula [MoCl5]2. This dark volatile solid is used in research to prepare other molybdenum compounds. It is moisture-sensitive and soluble in chlorinated solvents. Usually called molybdenum pentachloride, it is in fact a dimer with the formula Mo2Cl10.

Rhenium pentachloride

Rhenium pentachloride is an inorganic compound of chlorine and rhenium. The compound has the formula Re2Cl10 but it is usually referred to as rhenium pentachloride. It is a red-brown solid.

Niobium pentoxide

Niobium pentoxide is the inorganic compound with the formula Nb2O5. It is a colorless insoluble solid that is fairly unreactive. It is the main precursor to all materials made of niobium, the dominant application being alloys, but other specialized applications include capacitors, lithium niobate, and optical glasses.

Niobium(IV) chloride

Niobium(IV) chloride, also known as niobium tetrachloride, is the chemical compound of formula NbCl4. This compound exists as dark violet crystals, is highly sensitive to air and moisture, and disproportiates into niobium(III) chloride and niobium(V) chloride when heated.

Niobium oxychloride

Niobium oxychloride is the inorganic compound with the formula NbOCl3. It is a white, crystalline, diamagnetic solid. It is often found as an impurity in samples of niobium pentachloride, a common reagent in niobium chemistry.

Molecular oxohalides (oxyhalides) are a group of chemical compounds in which both oxygen and halogen atoms are attached to another chemical element A in a single molecule. They have the general formula AOmXn, X = F, Cl, Br, I. The element A may be a main group element, a transition element or an actinide. The term oxohalide, or oxyhalide, may also refer to minerals and other crystalline substances with the same overall chemical formula, but having an ionic structure.

Niobium(V) ethoxide

Niobium(V) ethoxide is an metalorganic compound with formula Nb2(OC2H5)10. It is a colorless liquid that dissolves in some organic solvents but hydrolyzes readily. It is mainly used for the sol-gel processing of materials containing niobium oxides.

Tantalum(V) ethoxide

Tantalum(V) ethoxide is a metalorganic compound with formula Ta2(OC2H5)10, often abbreviated as Ta2(OEt)10. It is a colorless solid that dissolves in some organic solvents but hydrolyzes readily. It is used to prepare films of tantalum(V) oxide.

Organotantalum chemistry

Organotantalum chemistry is the chemistry of chemical compounds containing a carbon-to-tantalum chemical bond. A wide variety of compound have been reported, initially with cyclopentadienyl and CO ligands. Oxidation states vary from Ta(V) to Ta(-I).

Niobium(III) chloride also known as niobium trichloride is a compound of niobium and chlorine. The binary phase NbCl3 is not well characterized but many adducts are known.

Tantalum(III) chloride Chemical compound

Tantalum(III) chloride or tantalum trichloride is non-stoichiometric with a range of composition from TaCl2.9 to TaCl3.1 Anionic and neutral clusters containing Ta(III) chloride include [Ta6Cl18]4− and [Ta6Cl14](H2O)4.

Transition metal chloride complex Coordination complex

In chemistry, a transition metal chloride complex is a coordination complex that consists of a transition metal coordinated to one or more chloride ligand. The class of complexes is extensive.


  1. Lide, David R., ed. (2006). CRC Handbook of Chemistry and Physics (87th ed.). Boca Raton, FL: CRC Press. ISBN   0-8493-0487-3.
  2. Rabe, Susanne; Müller, Ulrich (2000). "Crystal structure of tantalum pentachloride, (TaCl5)2". Z. Kristallogr. - New Cryst. Struct. 215 (1): 1–2. doi: 10.1515/ncrs-2000-0102 .
  3. F. Fairbrother (1967). The Chemistry of Niobium and Tantalum . Elsevier.
  4. 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. doi:10.1021/ja01139a524.
  5. F. A. Cotton, G. Wilkinson, Advanced Inorganic Chemistry (4th ed.), Wiley, New York, 1980.
  6. Duraisamy, Thirumalai; Hay, Daniel N. T.; Messerle, Louis (2014). "Octahedral Hexatantalum Halide Clusters". Inorganic Syntheses: Volume 36. Inorganic Syntheses. 36. pp. 1–8. doi:10.1002/9781118744994.ch1. ISBN   9781118744994.
  7. Thaxton, C. B.; Jacobson, R. A. (1971). "The Crystal Structure of H2(Ta6Cl18)(H2O)6". Inorganic Chemistry. 10: 1460–1463. doi:10.1021/ic50101a029.CS1 maint: uses authors parameter (link)

Further reading