Tantalum(V) ethoxide

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Tantalum(V) ethoxide
Names
IUPAC name
Tantalum(V) ethoxide
Other names
  • Tantalum ethylate
  • Tantalum(V) ethylate
  • Pentaethyl tantalate
  • Tantalum pentaethoxide
  • Pentaethoxytantalum(V)
  • Tantalum(5+) pentaethanolate
Identifiers
3D model (
JSmol
)
ChemSpider
ECHA InfoCard
 100.025.464 Edit this at Wikidata
EC Number
  • 228-010-2
  • [Ta+5].[O-]CC.[O-]CC.[O-]CC.[O-]CC.[O-]CC
Properties
C10H25O5Ta
Molar mass 406.25 g mol−1
Appearance Colorless liquid
Density 1.566 g/cm3 (at 25 °C)
Melting point 21 °C (70 °F; 294 K)
Boiling point 145 °C (293 °F; 418 K) at 0.0133 kPa
reacts
Solubility Organic solvents
1.488[1]
Hazards[2]
GHS labelling:
GHS02: FlammableGHS05: CorrosiveGHS07: Exclamation mark
Danger
H226, H314, H319, H335
P280, P305+P351+P338
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g. white phosphorusSpecial hazard W: Reacts with water in an unusual or dangerous manner. E.g. sodium, sulfuric acid
2
1
2
W
Flash point 31 °C; 87 °F; 304 K
Safety data sheet (SDS) External MSDS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Tantalum(V) ethoxide is a

metalorganic compound with formula Ta2(OC2H5)10, often abbreviated as Ta2(OEt)10. It is a colorless solid that dissolves in some organic solvents but hydrolyzes readily.[3]
It is used to prepare films of tantalum(V) oxide.

Structure

Tantalum(V) alkoxides typically exist as

cis to one another within the coordination sphere
. The formula [(EtO)4Ta(μ-OEt)]2 more comprehensively represents this dimeric structure, although the simplified formula is commonly used for most purposes.

Preparation

5 kg of distilled pure tantalum ethoxide, showing that it is a solid at 20 °C.

Several approaches are known for preparing tantalum(V) ethoxide.

Tantalum pentachloride, Ta2Cl10, provides a convenient starting point. To avoid the generation of mixed chloride-ethoxide species, a base such as ammonia is usually added to trap liberated HCl:[8]

10 EtOH + Ta2Cl10 + 10 NH3 → Ta2(OEt)10 + 10 NH4Cl

Salt metathesis using an alkali metal alkoxide can be used as well:[8]

10 NaOEt + Ta2Cl10 → Ta2(OEt)10 + 10 NaCl

The same compound can be prepared

half-equations and the overall equation[9]
for this reaction are:

cathode: 2 EtOH + 2 e− → 2 EtO− + H2
anode: Ta → "Ta5+" + 5 e−
overall: 2 Ta + 10 EtOH → 2 "Ta5+" + 10 EtO− + 5 H2 → Ta2(OEt)10 + 5 H2

Commercial production of tantalum(V) ethoxide using this electrochemical approach has been employed in Russia.[9] The compound can also be prepared by direct reaction of tantalum metal with ethanol, in which case the overall equation is the same as that shown above for the electrochemical approach.[8]

Since the 1970s, Bayer of Germany had been producing tantalum(V) ethoxide in Leverkusen, however following the break-up of Bayer, production moved to Heraeus. Meanwhile, Inorgtech (later MultiValent), started production in 1974 in Cambridge, UK. Both routes involved the direct reaction of the metal chloride with alcohol in the presence of solvents to give a product of 99.999%+ purity.[citation needed]

Reactions

The most important reaction of tantalum alkoxides is

tantalum(V) oxide film by hydrolysis[3]
can be described by this simplified equation:

Ta2(OC2H5)10 + 5 H2O → Ta2O5 + 10 C2H5OH

Tantalum(V) ethoxide

tetraethoxysilane, Si(OEt)4, or di-t-butyoxydiacetoxysilane, Si(OC(CH3)3)2(OOCCH3)2, then tantalum(V) ethoxide is introduced.[10] As in the case of niobium(V) ethoxide, the ethoxide precursor thermally decomposes to produce the oxide layer with the associated release of diethyl ether
:

Ta2(OEt)10 → Ta2O5 + 5 Et–O–Et

Pyrolysis also produces a tantalum(V) oxide film by chemical vapor deposition in which case the tantalum(V) ethoxide is completely oxidised, producing carbon dioxide and water vapor:[11]

Ta2(OC2H5)10 + 30 O2 → Ta2O5 + 20 CO2 + 25 H2O

Amorphous tantalum(V) oxide films can also be prepared by atomic layer deposition or by a pulsed chemical vapour deposition technique in which tantalum(V) ethoxide and tantalum(V) chloride are applied alternately.[12] At temperatures approaching 450 °C the films produced have refractive indices and permittivity properties similar to those produced from conventional approaches.[12] The preparation of these films occurs with the loss of chloroethane:[12]

Ta2(OC2H5)10 + Ta2Cl10 → 2 Ta2O5 + 10 C2H5Cl

Sol-gel processing also produces thin films of tantalum(V) oxide[13] using a similar chemical approach. Sol-gel routes using tantalum(V) ethoxide to generate layered perovskite materials have also been developed.[14]

Applications

It is mainly used for the manufacture of

sol-gel processing.[13] These materials have semiconductor,[12] electrochromic,[15] and optical[10]
applications.

Tantalum(V) oxide films have a variety of applications including as optical films with refractive indices as high as 2.039

annealling.[17] Chemical vapour deposition allows control of the thickness of the film on a nanometre scale, which is essential for some applications. Direct pyrolysis is convenient for optical applications,[10] where transparent materials with low light loss due to absorption is important,[16] and has also been used to prepare nitride read-only memory.[11] Electrochromism is the property of some materials to change color when charge is applied,[18] and is the means by which so-called smart glass operates. Films produced by tantalum(V) ethoxide hydrolysis has been used to prepare amorphous tantalum(V) oxide films suitable for electrochromic applications.[15]

Mixed-metal thin-films have also been prepared from this compound. For example, lithium tantalate, LiTaO3, films are desirable for their

metalorganic vapour phase epitaxy (a form of chemical vapor deposition).[19] Films of strontium tantalate, Sr(TaO3)2, have also been prepared using atomic layer deposition approaches and their properties investigated.[20]

Tantalum(V) ethoxide condenses with carboxylic acids to give oxo-alkoxide-carboxylates, e.g., Ta4O4(OEt)8(OOCCH3)4.[8] The Ta4O4 core of such compounds form a cubane-type cluster.

References

  1. ^ "Tantalum Ethoxide and Niobium Ethoxide". Materian Advanced Chemicals. Retrieved 19 October 2012.
  2. ^ "Tantalum (V) ethoxide 99.98% trace metals basis". Sigma Aldrich. Retrieved 18 October 2012.
  3. ^
    ISBN 0-8493-0487-3
    .
  4. S2CID 98638647
    .
  5. doi:10.1139/v61-239
    .
  6. ^
    doi:10.1016/0277-5387(96)00092-7
    .
  7. ISBN 9780470167045
    .
  8. ^
    ISBN 978-0-12-409547-2
    .
  9. ^
    ISBN 978-0-08-048832-5
    .
  10. ^
    ISBN 9780819453136
    .
  11. ^ a b US patent 6461949, Chang, K. K. & Chen, C.-H., "Method For Fabricating A Nitride Read-Only-Memory (NROM)", issued 2002-10-08, assigned to Macronix International Co. Ltd. 
  12. ^
    doi:10.1021/cm001017j
    .
  13. ^
    ISBN 9783527318605
    .
  14. ISBN 9780125137553
    .
  15. ^
    doi:10.1016/S0927-0248(99)00041-0
    .
  16. ^
    doi:10.1016/j.optmat.2012.02.023
    .
  17. doi:10.1016/S0955-2219(03)00230-9
    .
  18. PMID 12449538
    .
  19. doi:10.1063/1.110061
    .
  20. S2CID 94199325
    .
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