:Tantalum(V) chloride

{{chem2|TaCl5}} crystallizes in the monoclinic space group C2/m.{{cite journal |first1=Susanne|last1 = Rabe|first2=Ulrich|last2=Müller|title = Crystal structure of tantalum pentachloride, (TaCl₅)₂|journal = Z. Kristallogr. - New Cryst. Struct.|year = 2000|volume = 215|issue=1|pages=1–2|doi=10.1515/ncrs-2000-0102|doi-access=free| bibcode=2000ZK....215....1R }}{{primary source inline|date=May 2025}}{{primary source inline|date=May 2025}} 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, {{chem2|TaCl5}} is monomeric. This monomer adopts a trigonal bipyramidal structure, like that of Phosphorus pentachloride.{{cite book | author = Fairbrother, F. | year = 1967 | title = The Chemistry of Niobium and Tantalum | edition = | pages = | location = | publisher = Elsevier | isbn = | url = https://archive.org/details/chemistryofniobi0000fair | url-access = registration | access-date = | quote = }}{{full|date=May 2025}}{{page needed|date=May 2025}}

{{unreferenced section|date=May 2025}}

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. {{chem2|TaCl5}} is purified by sublimation to give white needles.{{Contradictory inline|reason=Lead, infobox, and Physical properties section all present discrepant, unique descriptions of form.|date=May 2025}}

{{refimprove section|date=May 2025}}

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.{{cite journal|last1=Young|first1=Ralph C.|last2=Brubaker|first2=Carl H.|journal=Journal of the American Chemical Society|title = Reaction of Tantalum with Hydrogen Chloride, Hydrogen Bromide and Tantalum Pentachloride; Action of Hydrogen on Tantalum Pentachloride|year=1952|volume=74|issue=19|page=4967|doi=10.1021/ja01139a524|bibcode=1952JAChS..74.4967Y }}{{primary source inline|date=May 2025}}{{primary source inline|date=May 2025}}

:{{chem2|2 Ta + 5 Cl2 → 2 TaCl5}}

:{{chem2|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

:{{chem2|Ta2O5 + 5 SOCl2 → 2 TaCl5 + 5 SO2}}

Tantalum pentachloride is commercially available, however samples can be contaminated with tantalum(V) oxytrichloride ({{chem2|TaOCl3}}), formed by hydrolysis.

{{refimprove section|date=May 2025}}

{{chem2|TaCl5}} is electrophilic and it behaves like a Friedel–Crafts catalyst, similar to Aluminium chloride. It forms adducts with a variety of Lewis bases.{{cite book | author = Cotton, F. A. & Wilkinson, G. | year = 1980 | title = Advanced Inorganic Chemistry | edition = 4th | pages = | location = New York, NY | publisher = John Wiley & Sons | isbn = | url = | url-access = | access-date = | quote = }}{{full|date=May 2025}} Information on these authors is available via the articles on F. Albert Cotton and Geoffrey Wilkinson.{{page needed|date=May 2025}}

{{chem2|TaCl5}} forms stable complexes with ethers:

:{{chem2|TaCl5 + R2O → TaCl5(OR2)}} (R = Me, Et)

{{chem2|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:

:{{chem2|TaCl5 + PCl5 → [PCl4]+[TaCl6]-}}

:{{chem2|TaCl5 + OPCl3 → [TaCl5(OPCl3)]}}

Tantalum pentachloride reacts with tertiary amines to give crystalline adducts.

:{{chem2|TaCl5 + 2 R3N → [TaCl5(NR3)]}}

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

:{{chem2|TaCl5 + 3 OPPh3 → [TaOCl3(OPPh3)]_{x}|}} ...

The presumed initial formation of adducts between {{chem2|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:

:{{chem2|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 tantalum(V) ethanolate {{chem2|Ta(OEt)5}}. Similarly {{chem2|TaCl5}} reacts with lithium methoxide in anhydrous methanol to form related methoxy derivatives:

:{{chem2|TaCl5 + 4 LiOMe → Ta(OMe)4Cl + 4 LiCl}}

Ammonia will displace most of the chloride ligands from {{chem2|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:

Image:EntryWithCollCode26094.png

:{{chem2|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:

:{{chem2|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 {{chem2|[Ta6Cl18](4−)}} and {{chem2|[Ta6Cl14](H2O)4}}.{{cite book | last1=Duraisamy|first1=Thirumalai|last2=Hay|first2=Daniel N. T.|last3=Messerle|first3=Louis| year=2014| chapter = Octahedral Hexatantalum Halide Clusters | title = Inorganic Syntheses | edition = | volume = 36 | pages = 1–8 | location = | publisher = | isbn = 9781118744994 | doi = 10.1002/9781118744994.ch1 | url = | url-access = | access-date = | quote = }}{{full|date=May 2025}}{{full|date=May 2025}}

{{reflist}}

• {{cite journal |first1=A.|last1 = Cowley |first2=F.|last2 = Fairbrother |first3=N.|last3 = Scott | journal = J. Chem. Soc. |title = The Halides of Niobium (Columbium) and Tantalum. Part V. Diethyl Ether Complexes of the Pentachlorides and Pentabromides; the Solubility of Tantalum Pentaiodide in Ether | year = 1958 | pages = 3133–3137|doi = 10.1039/JR9580003133}}
• {{cite journal|first1=G. A.|last1=Ozin|first2=R. A.|last2=Walton|journal=J. Chem. Soc. A|year=1970|pages=2236–2239|doi=10.1039/j19700002236|title = 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)}}
• {{cite journal |first1=C.|last1 = Đorđević |first2=V.|last2 = Katović | journal = J. Chem. Soc. A | year = 1970 | pages = 3382–3386 | doi = 10.1039/j19700003382 | title = 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}}
• {{cite journal |first1=J. I.|last1 = Bullock |first2=F. W. |last2 = Parrett |first3=N. J. |last3 = Taylor | journal = J. Chem. Soc., Dalton Trans. |issue = 5 | year = 1973 | pages = 522–524|title = Some Metal Halide–Phosphorus Halide–Alkyl Halide Complexes. Part II. Reactions with Niobium and Tantalum Pentachlorides and Tungsten Hexachloride |doi = 10.1039/DT9730000522}}

{{Commons category|Tantalum(V) chloride}}

• [http://webbook.nist.gov/chemistry/ NIST Standard Reference Database]

{{Tantalum compounds}}

{{Chlorides}}

{{DEFAULTSORT:Tantalum(V) Chloride}}

Category:Tantalum(V) compounds

Category:Chlorides

Category:Metal halides