Niobium(V) ethoxide is an metalorganic compound with formula Nb
2(OC
2H
5)
10. It is a colorless liquid that dissolves in some organic solvents but hydrolyzes readily.
[W. M. Haynes. CRC Handbook of Chemistry and Physics, 93rd Edition. Physical Constants of Inorganic Compounds.] It is mainly used for the
sol-gel processing of materials containing niobium oxides.
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Structure
Metal alkoxides rarely adopt monomeric structures, and niobium(V) ethoxide is no exception. Early studies established that niobium alkoxides aggregate in solution as dimers. Subsequent crystallographic analysis established that the methoxide and isopropoxides of niobium adopt bioctahedral structures.ligand
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 elec ...
oxygen atoms of the Nb2(OEt)10 molecule in solution define a pair of octahedra sharing a common edge with the two niobium atoms located at their centres. From a bonding perspective, each niobium centre is surrounded octahedrally by four monodentate
In coordination chemistry, denticity () refers to the number of donor groups in a given ligand that bind to the central metal atom in a coordination complex. In many cases, only one atom in the ligand binds to the metal, so the denticity equals ...
and two bridging ethoxide ligands. The oxygen atoms of the bridging ethoxides are each bonded to both niobium centres, and these two ligands are ''cis'' to one another within the coordination sphere
In coordination chemistry, the first coordination sphere refers to the array of molecules and ions (the ligands) directly attached to the central metal atom. The second coordination sphere consists of molecules and ions that attached in various ...
. The formula EtO)4Nb(μ-OEt)sub>2 more comprehensively represents this dimeric structure, though the simplified formula is commonly used for most purposes.
Preparation and reactions
This compound is prepared by salt metathesis
A salt metathesis reaction, sometimes called a double displacement reaction, is a chemical process involving the exchange of bonds between two reacting chemical species which results in the creation of products with similar or identical bonding a ...
from 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. NbC ...
(Et = C2H5):
:10 NaOEt + Nb2Cl10 → Nb2(OC2H5)10 + 10 NaCl
The most important reaction of niobium alkoxides is their hydrolysis to produce films and gels of niobium oxides.[U. Schubert "Sol–Gel Processing of Metal Compounds" Comprehensive Coordination Chemistry II 2003, Pages 629–656 Volume 7. ] Although these reactions are complex, they can be described by this simplified equation:
:Nb2(OC2H5)10 + 5 H2O → Nb2O5 + 10 HOEt
The thermal decomposition of Nb(OC2H5)5 begins above 325 – 350 °C. This can be observed with QMS as an increasing amount of ethanol and ethane
Ethane ( , ) is an organic chemical compound with chemical formula . At standard temperature and pressure, ethane is a colorless, odorless gas. Like many hydrocarbons, ethane is isolated on an industrial scale from natural gas and as a petroc ...
released. Diethyl ether
Diethyl ether, or simply ether, is an organic compound in the ether class with the formula , sometimes abbreviated as (see Pseudoelement symbols). It is a colourless, highly volatile, sweet-smelling ("ethereal odour"), extremely flammable li ...
, C2H5OC2H5, and niobium(V) oxide are the decomposition products released following an atomic layer deposition or chemical vapor deposition process. The decomposition reaction can be summarised as:
References
{{Niobium compounds
Ethoxides
Niobium(V) compounds