- Tungsten(VI) fluoride
Chembox new
ImageFileL1 = Tungsten(VI) fluoride.jpg
ImageSizeL1 = 100px
ImageNameL1 = Tungsten(VI) fluoride
ImageFileR1 = Tungsten-hexafluoride-3D-balls.png
ImageSizeR1 = 100px
ImageNameR1 = Ball-and-stick model of tungsten hexafluoride
IUPACName = Tungsten(VI) fluoride
OtherNames = Tungsten hexafluoride
Section1 = Chembox Identifiers
CASNo = 7783-82-6
Section2 = Chembox Properties
Formula = WF6
MolarMass = 297.83 g/mol
Appearance = Colorless gas.
Density = 13.1 g/L, gas.
Solubility = Hydrolyzes.
MeltingPt = 2.3°C (275.45 K)
BoilingPt = 17.1°C (290.25 K)
Section3 = Chembox Structure
MolShape = Octahedral
Dipole = 0 D
Section7 = Chembox Hazards
MainHazards = Corrosive, highly toxic.
Section8 = Chembox Related
OtherAnions =Tungsten(VI) chloride ,Tungsten(VI) bromide
OtherCations =Chromium(V) fluoride ,Molybdenum(VI) fluoride
OtherCpds =Tungsten(IV) fluoride ,Tungsten(V) fluoride ,
Uranium hexafluoride Tungsten(VI) fluoride, also known as tungsten hexafluoride, is a colorless gas. It is nonflammable, but highly corrosive and very toxic. It is the densest known gas at a pressure of 1 atm and room temperature (25 °C). The molecule is octahedral with the symmetry point group of Oh.The gas is most commonly used in the production of
semiconductor circuits andcircuit boards , through the process ofchemical vapor deposition .Kirss, Rein U., Lamartine Meda. "Chemical Vapor Deposition of Tungsten Oxide." "Applied Organometallic Chemistry" 12 (1998): 155–160.]Industrial Synthesis
Tungsten hexafluoride of a purity high enough for
semiconductor CVD is produced by the reaction offluorine gas withtungsten metal. The metal is placed in a heated reactor, slightly pressurized to 1.2 to 2.0 psi, with a constant flow of WF6 infused with a small amount offluorine gas. [http://www.patentstorm.us/patents/6544889.html Patent Storm] ]Reactions
WF6("g") + H2("g") + Al("s") → W("s") + HF("g") + AlF3("s")
This reaction occurs when
tungsten is deposited onaluminium .One application of this would be in the production of studs for semiconductor circuits. [http://www.priorartdatabase.com/IPCOM/000038388/ Ip.com] ]Tungsten can also be deposited on a
silicon wafer or other semiconducting material viachemical vapor deposition , or CVD, as follows: [http://www.mne.umd.edu/grad/courses/old_courses_stuff_saved/659s_mats_&_proc_for_microelectronics/659s_spring_1998/enma659S_spr98_final_project_results/wcvd/sih4.html James Clark School of Engineering] ]WF6("g") + W* → WF6*
2 SiH4("g") + WF6* → W("s") + 2 SiHF3(g) + 3 H2("g")
The
silane SiH4 reduces the tungsten from anoxidation state of 6+ (VI) to its elemental state of zero.afety
On contact with water tungsten(VI) fluoride forms
hydrofluoric acid (HF), which can penetrate the skin and cause damage to the subdermal tissues and bone. Inhalation burns the respiratory tract and can be toxic. WF6 is alachrymator which causes tearing and irritation of the eyes. Contact causes burns to the eyes, skin and mucous membranes. [https://www.mathesongas.com/msds/index.aspx Matheson Gas] ]In "",
Oliver Sacks comments on how he wanted WF6-filled balloons for his 65th birthday, but the gas was too reactive. Had one of the balloons popped, the tungsten(VI) fluoride would have reacted with moisture in the air to formhydrogen fluoride .References
External links
* [http://www.npi.gov.au/database/substance-info/profiles/44.html National Pollutant Inventory - Flouride and compounds fact sheet]
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