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 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. Synthesis left, 184px, Structure of NbCl3(dimethoxyethane)(3-hexyne). Nb ...

and

niobium(V) chloride 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. NbCl ...

when heated.Macintyre, J.E.; Daniel, F.M.; Chapman and Hall; Stirling, V.M. Dictionary of Inorganic Compounds. 1992, Cleveland, OH: CRC Press, p. 2957

Structure and properties

In the solid state, niobium(IV) chloride exists as chains of edge-sharing octahedra with alternating Nb-Nb distances of lengths 302.9 and 379.4 pm. The shorter distances correspond to Nb-Nb bonds, which result in the compound's diamagnetism. Its structure is very similar to that of

tungsten(IV) chloride Tungsten(IV) chloride is an inorganic compound with the formula WCl4. It is a diamagnetic black solid. The compound is of interest in research as one of a handful of binary tungsten chlorides. Structure and preparation WCl4 is usually prepar ...

. Other

coordination complexes A coordination complex consists of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of bound molecules or ions, that are in turn known as ''ligands'' or complexing agents. Many m ...

with the formula NbCl₄L₂, such as tetrachlorobis(tetrahydrofuran) niobium, only form monomers resulting in one unpaired electron in the d_''xy'' orbital, making the compounds paramagnetic. Niobium chloride rapidly oxidizes and hydrolyzes in air to form

niobium(V) oxide Niobium pentoxide is the inorganic compound with the formula Nb2 O5. 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 allo ...

Preparation

Niobium(IV) chloride is typically produced by allowing elemental

niobium Niobium is a chemical element with chemical symbol Nb (formerly columbium, Cb) and atomic number 41. It is a light grey, crystalline, and ductile transition metal. Pure niobium has a Mohs hardness rating similar to pure titanium, and it has sim ...

and

crystals to react over several days in a temperature gradient, with the metal around 400 °C and the salt around 250 °C. :4 NbCl₅ + Nb → 5 NbCl₄ Niobium (IV) chloride can also prepared by a similar reduction of

niobium pentachloride 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. NbCl ...

with powdered

aluminium Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...

. :3 NbCl₅ + Al → 3 NbCl₄ + AlCl₃ A similar technique is also used in the synthesis of

niobium(IV) bromide Niobium is a chemical element with chemical symbol Nb (formerly columbium, Cb) and atomic number 41. It is a light grey, crystalline, and ductile transition metal. Pure niobium has a Mohs hardness rating similar to pure titanium, and it has s ...

and

tantalum(IV) chloride Tantalum is a chemical element with the symbol Ta and atomic number 73. Previously known as ''tantalium'', it is named after Tantalus, a villain in Greek mythology. Tantalum is a very hard, ductile, lustrous, blue-gray transition metal that is ...

. Niobium(IV) iodide exists as well and may be synthesized by thermal decomposition of

niobium(V) iodide Niobium(V) iodide is the inorganic compound with the formula Nb2I10. Its name comes from the compound's empirical formula, NbI5. It is a diamagnetic, yellow solid that hydrolyses readily. The compound adopts an edge-shared bioctahedral structur ...

. At 400 °C NbCl₄ disproportiates: :2 NbCl₄ → NbCl₃ + NbCl₅

Reactions

The disproportiation of niobium(IV) chloride can be used to make tetrachlorobis(tetrahydrofuran) niobium, a useful synthon in Nb^IV chemistry due to the lability of the attached

tetrahydrofuran Tetrahydrofuran (THF), or oxolane, is an organic compound with the formula (CH2)4O. The compound is classified as heterocyclic compound, specifically a cyclic ether. It is a colorless, water-miscible organic liquid with low viscosity. It is ma ...

ligands In coordination chemistry, a ligand is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's electro ...

.Hubert-Pfalzgraf, L.G. Niobium & Tantalum: Inorganic & Coordination Chemistry. 2006: John Wiley & Sons, Ltd. This compound can be synthesized by first reacting NbCl₅ with

acetonitrile Acetonitrile, often abbreviated MeCN (methyl cyanide), is the chemical compound with the formula and structure . This colourless liquid is the simplest organic nitrile (hydrogen cyanide is a simpler nitrile, but the cyanide anion is not clas ...

followed by addition of

to the resultant solid by the following reaction. : 3 NbCl₅ + Al + 3 CH₃CN → 3 NbCl₄(NCCH₃)₃ + AlCl₃ : 3 NbCl₄(NCCH₃)₃ + AlCl₃ + 3 C₄H₈O → 3 NbCl₄(thf)₂ + 9 MeCN + AlCl₃(thf)

References

{{Chlorides Niobium(IV) compounds Chlorides Metal halides