Niobium(IV) chloride
Encyclopedia
Niobium 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.
with alternating Nb-Nb distances of lengths 302.9 and 379.4 pm. The shorter distances correspond to Nb-Nb bonds, forming a polymer
resulting in the compound’s diamagnetism
. This metal bond forms as niobium
forms d1 compounds
in its +4 oxidation state
, resulting in lone electrons. Other coordination complexes with the formula NbCl4L2, such as tetrachlorobis(tetrahydrofuran) niobium, only form monomers resulting in one unpaired electron in the dxy orbital, making the compounds paramagnetic.
Niobium chloride rapidly oxidizes and hydrolyzes in air to form niobium(V) oxide.
and niobium(V) chloride
crystals to react over several days in a temperature gradient, with the metal around 400 °C and the salt around 250 °C.
Niobium (IV) chloride can also prepared by a similar reduction of niobium pentachloride with powdered aluminium
.
A similar technique is also used in the synthesis of niobium(IV) bromide and tantalum(IV) chloride. Niobium(IV) iodide exists as well and may be synthesized by thermal decomposition of niobium(V) iodide.
At 400 °C NbCl4 disproportiates:
in NbIV chemistry due to the lability of the attached tetrahydrofuran
ligands.This compound can be synthesized by first reacting NbCl5 with aluminium
in acetonitrile
followed by addition of tetrahydrofuran
to the resultant solid by the following reaction.
Niobium chloride has been used in the syntheses of indazoles which can be used as LXR
or Liver X receptor
inhibitors.
Niobium(V) chloride
Niobium 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...
when heated.
Structure and properties
In the solid state, niobium(IV) chloride exists as chains of edge-sharing octahedraOctahedral molecular geometry
In chemistry, octahedral molecular geometry describes the shape of compounds where in six atoms or groups of atoms or ligands are symmetrically arranged around a central atom, defining the vertices of an octahedron...
with alternating Nb-Nb distances of lengths 302.9 and 379.4 pm. The shorter distances correspond to Nb-Nb bonds, forming a polymer
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...
resulting in the compound’s diamagnetism
Diamagnetism
Diamagnetism is the property of an object which causes it to create a magnetic field in opposition to an externally applied magnetic field, thus causing a repulsive effect. Specifically, an external magnetic field alters the orbital velocity of electrons around their nuclei, thus changing the...
. This metal bond forms as niobium
Niobium
Niobium or columbium , is a chemical element with the symbol Nb and atomic number 41. It's a soft, grey, ductile transition metal, which is often found in the pyrochlore mineral, the main commercial source for niobium, and columbite...
forms d1 compounds
D electron count
The d electron count is a chemistry formalism used to describe the electron configuration of the valence electrons of a transition metal center in a coordination complex. The d electron count is an effective way to understand the geometry and reactivity of transition metal complexes...
in its +4 oxidation state
Oxidation state
In chemistry, the oxidation state is an indicator of the degree of oxidation of an atom in a chemical compound. The formal oxidation state is the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic. Oxidation states are typically represented by...
, resulting in lone electrons. Other coordination complexes with the formula NbCl4L2, such as tetrachlorobis(tetrahydrofuran) niobium, only form monomers resulting in one unpaired electron in the dxy orbital, making the compounds paramagnetic.
Niobium chloride rapidly oxidizes and hydrolyzes in air to form niobium(V) oxide.
Preparation
Niobium(IV) chloride is typically produced by allowing elemental niobiumNiobium
Niobium or columbium , is a chemical element with the symbol Nb and atomic number 41. It's a soft, grey, ductile transition metal, which is often found in the pyrochlore mineral, the main commercial source for niobium, and columbite...
and niobium(V) chloride
Niobium(V) chloride
Niobium 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...
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 with powdered aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
.
- 3 NbCl5 + Al → 3 NbCl4 + AlCl3
A similar technique is also used in the synthesis of niobium(IV) bromide and tantalum(IV) chloride. Niobium(IV) iodide exists as well and may be synthesized by thermal decomposition of niobium(V) iodide.
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 synthonSynthon
A synthon is a concept in retrosynthetic analysis. It is defined as a structural unit within a molecule which is related to a possible synthetic operation. The term was coined by E.J. Corey...
in NbIV chemistry due to the lability of the attached tetrahydrofuran
Tetrahydrofuran
Tetrahydrofuran is a colorless, water-miscible organic liquid with low viscosity at standard temperature and pressure. This heterocyclic compound has the chemical formula 4O. As one of the most polar ethers with a wide liquid range, it is a useful solvent. Its main use, however, is as a precursor...
ligands.This compound can be synthesized by first reacting NbCl5 with aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
in acetonitrile
Acetonitrile
Acetonitrile is the chemical compound with formula . This colourless liquid is the simplest organic nitrile. It is produced mainly as a byproduct of acrylonitrile manufacture...
followed by addition of tetrahydrofuran
Tetrahydrofuran
Tetrahydrofuran is a colorless, water-miscible organic liquid with low viscosity at standard temperature and pressure. This heterocyclic compound has the chemical formula 4O. As one of the most polar ethers with a wide liquid range, it is a useful solvent. Its main use, however, is as a precursor...
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)
Niobium chloride has been used in the syntheses of indazoles which can be used as LXR
Liver X receptor
The liver X receptor is a member of the nuclear receptor family of transcription factors and is closely related to nuclear receptors such as the PPARs, FXR and RXR. Liver X receptors are important regulators of cholesterol, fatty acid, and glucose homeostasis...
or Liver X receptor
Liver X receptor
The liver X receptor is a member of the nuclear receptor family of transcription factors and is closely related to nuclear receptors such as the PPARs, FXR and RXR. Liver X receptors are important regulators of cholesterol, fatty acid, and glucose homeostasis...
inhibitors.