Tantalum(V) chloride

Last updated
Tantalum(V) chloride
TaCl5structure.jpg
Names
IUPAC names
Tantalum(V) chloride
Tantalum pentachloride
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.028.869 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 231-755-6
PubChem CID
UNII
  • Key: OEIMLTQPLAGXMX-UHFFFAOYSA-I
  • InChI=1S/5ClH.Ta/h5*1H;/q;;;;;+5/p-5
  • Cl[Ta](Cl)(Cl)(Cl)Cl
Properties
TaCl5
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)
reacts
Solubility chloroform, CCl4
+140.0×10−6 cm3/mol
Structure
Monoclinic, mS72
C2/m, No. 12
Thermochemistry
Std molar
entropy (S⦵298)
221.75 J K−1 mol−1
-858.98 kJ/mol
Hazards
GHS labelling:
GHS-pictogram-acid.svg GHS-pictogram-exclam.svg
Danger
H302, H314
P280, P305+P351+P338, P310
NFPA 704 (fire diamond)
NFPA 704.svgHealth 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
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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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.

Contents

Structure

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.

Synthesis

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.

Reactions

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+
4][TaCl−
6]
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

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

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<span class="mw-page-title-main">Europium(III) chloride</span> Chemical compound

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<span class="mw-page-title-main">Phosphorus pentachloride</span> Chemical compound

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

<span class="mw-page-title-main">Phosphorus trichloride</span> Chemical compound

Phosphorus trichloride is an inorganic compound with the chemical formula PCl3. A colorless liquid when pure, it is an important industrial chemical, being used for the manufacture of phosphites and other organophosphorus compounds. It is toxic and reacts readily with water to release hydrogen chloride.

<span class="mw-page-title-main">Niobium(V) chloride</span> 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.

<span class="mw-page-title-main">Antimony pentachloride</span> Chemical compound

Antimony pentachloride is a chemical compound with the formula SbCl5. It is a colourless oil, but typical samples are yellowish due to dissolved chlorine. Owing to its tendency to hydrolyse to hydrochloric acid, SbCl5 is a highly corrosive substance and must be stored in glass or PTFE containers.

<span class="mw-page-title-main">Molybdenum(V) chloride</span> Chemical compound

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<span class="mw-page-title-main">Rhenium pentachloride</span> Chemical compound

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.

Martin Arthur Bennett FRS is an Australian inorganic chemist. He gained recognition for studies on the co-ordination chemistry of tertiary phosphines, olefins, and acetylenes, and the relationship of their behaviour to homogeneous catalysis.

<span class="mw-page-title-main">Niobium pentoxide</span> Chemical compound

Niobium pentoxide is the inorganic compound with the formula Nb2O5. A colorless, insoluble, and fairly unreactive solid, it is the most widespread precursor for other compounds and materials containing niobium. It is predominantly used in alloying, with other specialized applications in capacitors, optical glasses, and the production of lithium niobate.

<span class="mw-page-title-main">Niobium(IV) chloride</span> Chemical compound

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.

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<span class="mw-page-title-main">Tantalum(III) chloride</span> Chemical compound

Tantalum(III) chloride or tantalum trichloride is non-stoichiometric chemical compound 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.

Manganese(III) chloride is the hypothetical inorganic compound with the formula MnCl3.

References

  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. Vol. 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.

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