Niobium(V) chloride

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Template:Chembox header | Niobium(V) chloride
Sample of niobium(V) chloride
Systematic name Niobium(V) chloride
Niobium pentachloride
Molecular formula NbCl5
Molar mass 270.17 g/mol
Density 2.75 g/cm3
Solubility (water) Decomposes
Solubility (dimethylformamide) Good
Melting point 204.7 °C
Boiling point 254 °C
CAS number [10026-12-7]
EINECS number 233-059-8
Template:Chembox header | Thermodynamic data
Standard enthalpy
of formation
-797.47 kJ/mol
Standard molar entropy
214.05 J.K−1.mol−1
Template:Chembox header | Safety data
EU classification not listed
Flash point non-flammable
RTECS number QU0350000
Template:Chembox header | Related compounds
Related chlorides Vanadium(IV) chloride
Tantalum(V) chloride
Template:Chembox header |Disclaimer and references

Niobium(V) chloride, also known as niobium pentachloride, is a yellow crystalline solid often used as a starting material in niobium chemistry. It is prepared by heating niobium metal in chlorine. It is often contaminated with small amounts of niobium(V) oxychloride, NbOCl3, formed by hydrolysis or from traces of oxygen during the preparation. NbCl5 may be purified by sublimation.

Structure and properties

Niobium(V) chloride forms chloro-bridged dimers in the solid state (see figure). Each niobium centre is six-coordinate, but the octahedral coordination is significantly distorted. The niobium–chlorine bond lengths are 225 pm (terminal) and 256 pm (bridging), while the Nb–Cl–Nb angle at the bridge is 101.3°. The Nb–Nb distance is 395.1 pm, too long for any metal-metal interaction. NbBr5, TaCl5 and TaBr5 are isostructural with NbCl5, but NbI5 and TaI5 have different structures.

Ball-and-stick model of niobium pentachloride
Ball-and-stick model of niobium pentachloride


Niobium(V) chloride is used in organic chemistry as a Lewis acid in activating alkenes for the carbonyl-ene reaction and the Diels-Alder reaction. Niobium chloride can also generate N-acyliminium compounds from certain pyrrolidines which are substrates for nucleophiles such as allyltrimethylsilane, indole, or the silyl enol ether of benzophenone[1].

N-acyliminium ion generated from niobium pentachloride
N-acyliminium ion generated from niobium pentachloride


  1. ^ Andrade, C. K. Z.; Rocha, R. O.; Russowsky, D.; & Godoy, M. N. (2005). Studies on the Niobium Pentachloride-Mediated Nucleophilic Additions to an Enantiopure Cyclic N-acyliminium Ion Derived from (S)-malic acid. J. Braz. Chem. Soc. 16: 535–539. Online Article (.PDF file)

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