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Revision as of 14:07, 6 December 2011 editBeetstra (talk | contribs)Edit filter managers, Administrators172,031 edits Saving copy of the {{chembox}} taken from revid 459790503 of page Silane for the Chem/Drugbox validation project (updated: '').  Latest revision as of 19:50, 29 October 2024 edit Mondtaler (talk | contribs)182 edits GHS04 and H280 specifically address hazards linked to the pressurized storage of gases. As storage methods can vary, these pictograms and hazard statements are not universally applicable to all gaseous compounds. Also added the 'toxic pictogram', as it is stated in the article that it's a poisonous gas.Tag: 2017 wikitext editor 
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{{Short description|Chemical compound (SiH4)}}
{{ambox | text = This page contains a copy of the infobox ({{tl|chembox}}) taken from revid of page ] with values updated to verified values.}}
{{About|the compound with chemical formula SiH<sub>4</sub>|the broader classes of compounds|Silanes}}
{{Chembox {{Chembox
| Watchedfields = changed
| verifiedrevid = 451777236
| verifiedrevid = 464390173
| ImageFileL1 = Silane-2D.png
| ImageFile1 = Silane-2D.svg
| ImageSizeL1 = 121
| ImageNameL1 = Stereo structural formula of silane with implit hydrogens | ImageName1 = Stereo structural formula of silane
| ImageFileR1 = Silane-3D-vdW.png | ImageFileL1 = Silane-3D-balls.png
| ImageNameL1 = Ball-and-stick model of silane
| ImageSizeR1 = 121
| ImageFileR1 = Silane-3D-vdW.png
| ImageNameR1 = Spacefill model of silane
| ImageNameR1 = Spacefill model of silane
| IUPACName = Silane
| IUPACName = Silane
| OtherNames = Monosilane<br />
| SystematicName = Silicane
Silicane<br />
| OtherNames = {{ubl
Silicon hydride<br />
| Monosilane
Silicon tetrahydride
| Silicon(IV) hydride
| Section1 = {{Chembox Identifiers
| Silicon tetrahydride
}}
| Section1 = {{Chembox Identifiers
| CASNo = 7803-62-5 | CASNo = 7803-62-5
| CASNo_Ref = {{cascite|correct|CAS}} | CASNo_Ref = {{cascite|correct|CAS}}
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 5J076063R1
| PubChem = 23953 | PubChem = 23953
| PubChem_Ref = {{Pubchemcite|correct|PubChem}}
| ChemSpiderID = 22393 | ChemSpiderID = 22393
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} | ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
Line 27: Line 32:
| SMILES = | SMILES =
| StdInChI_Ref = {{stdinchicite|correct|chemspider}} | StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/H4Si/h1H4 | StdInChI = 1S/SiH4/h1H4
| InChI = 1/H4Si/h1H4 | InChI = 1/SiH4/h1H4
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} | StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = BLRPTPMANUNPDV-UHFFFAOYSA-N | StdInChIKey = BLRPTPMANUNPDV-UHFFFAOYSA-N
| InChIKey = BLRPTPMANUNPDV-UHFFFAOYAE}} | InChIKey = BLRPTPMANUNPDV-UHFFFAOYAE}}
| Section2 = {{Chembox Properties | Section2 = {{Chembox Properties
| H = 4 | Si=1 | H=4
| Appearance = Colorless gas
| Si = 1
| Odor = Repulsive<ref name=PGCH/>
| ExactMass = 32.008226661 g mol<sup>−1</sup>
| Density = 1.313{{nbsp}}g/L<ref name=crc>Haynes, p. 4.87</ref>
| Appearance = Colourless gas
| Density = 1.342 g dm<sup>−3</sup>
| MeltingPtC = −185 | MeltingPtC = −185
| MeltingPt_ref=<ref name=crc/>
| BoilingPtC = −112}}
| BoilingPtC = −111.9
| Section3 = {{Chembox Structure
| BoilingPt_ref=<ref name=crc/>
| MolShape = ]
| Solubility = Reacts slowly<ref name=crc/>
r(Si-H) = 1.4798 angstroms
| VaporPressure = >1{{nbsp}}atm (20&nbsp;°C)<ref name=PGCH/>
| Dipole = 0 ]
| ConjugateAcid = Silanium (sometimes spelled silonium)
}} }}
| Section4 = {{Chembox Thermochemistry | Section3 = {{Chembox Structure
| MolShape = ] <br/>r(Si-H) = 1.4798{{nbsp}}Å<ref>Haynes, p. 9.29</ref>
| DeltaHf = 34.31kJ/mol
| Dipole = 0{{nbsp}}]
| Entropy = 204.6 J&thinsp;mol<sup>−1</sup>&thinsp;K<sup>−1</sup>
}}
| Section4 = {{Chembox Thermochemistry
| Thermochemistry_ref = <ref>Haynes, p. 5.14</ref>
| DeltaHf = 34.31{{nbsp}}kJ/mol
| DeltaGfree = 56.91{{nbsp}}kJ/mol
| Entropy = 204.61{{nbsp}}J/mol·K
| HeatCapacity = 42.81{{nbsp}}J/mol·K
}} }}
| Section7 = {{Chembox Hazards | Section7 = {{Chembox Hazards
| ExternalMSDS = | ExternalSDS =
| MainHazards = Extremely flammable, pyrophoric in air, toxic
| EUIndex = Not listed
| GHSPictograms = {{GHS02}} {{GHS06}}
| MainHazards = Extremely flammable, pyrophoric in air
| RPhrases = | GHSSignalWord = Danger
| HPhrases = {{H-phrases|220}}
| SPhrases =
| PPhrases = {{P-phrases|P210|P222|P230|P280|P377|P381|P403|P410+P403}}
| NFPA-H = 2 | NFPA-H = 2
| NFPA-F = 4 | NFPA-F = 4
| NFPA-R = 3 | NFPA-R = 3
| FlashPt = flammable gas | FlashPt = Not applicable, pyrophoric gas
| AutoignitionPt = ~
| Autoignition = 294 K (21 °C) (~70 °F)
| AutoignitionPtC = 18
| ExploLimits = 1.37–100% | ExploLimits = 1.37–100%
| PEL = 5 ppm (] TLV) | PEL = None<ref name=PGCH/>
| IDLH = N.D.<ref name=PGCH>{{PGCH|0556}}</ref>
| REL = TWA 5{{nbsp}}ppm (7{{nbsp}}mg/m<sup>3</sup>)<ref name=PGCH/>
}} }}
| Section8 = {{Chembox Related | Section8 = {{Chembox Related
| OtherFunction_label = tetrahydride compounds
| Function = monosilanes
| OtherFunction = ]<br />]<br />]<br />]
| OtherFunctn = ]<br />
| OtherCompounds = ]<br />]<br />]<br />]}}
]
| OtherCpds = ]<br />
]<br />
]<br />
]}}
}} }}

'''Silane''' ('''Silicane''') is an ] with ] {{chem2|SiH4}}. It is a colorless, ], ] with a sharp, repulsive, ] smell, somewhat similar to that of ].<ref>{{Greenwood&Earnshaw2nd}}</ref> Silane is of practical interest as a precursor to elemental ]. Silane with ]s are effective water repellents for mineral surfaces such as concrete and masonry. Silanes with both ] and ] attachments are used as coupling agents. They are commonly used to apply coatings to surfaces or as an adhesion promoter.<ref>{{Cite journal |last1=London |first1=Gábor |last2=Carroll |first2=Gregory T. |last3=Feringa |first3=Ben L. |date=2013 |title=Silanization of quartz, silicon and mica surfaces with light-driven molecular motors: construction of surface-bound photo-active nanolayers |url=http://xlink.rsc.org/?DOI=c3ob40276b |journal=Organic & Biomolecular Chemistry |language=en |volume=11 |issue=21 |pages=3477–3483 |doi=10.1039/c3ob40276b |pmid=23592007 |s2cid=33920329 |issn=1477-0520}}</ref>

==Production==

===Commercial-scale routes===
Silane can be produced by several routes.<ref name=Ullmann>{{Ullmann |author=Simmler, W. |title=Silicon Compounds, Inorganic |doi=10.1002/14356007.a24_001}}</ref> Typically, it arises from the reaction of hydrogen chloride with ]:
: {{chem2|Mg2Si + 4 HCl -> 2 MgCl2 + SiH4}}

It is also prepared from metallurgical-grade silicon in a two-step process. First, silicon is treated with ] at about 300&nbsp;°C to produce ], HSiCl3, along with ] gas, according to the ]
: {{chem2|Si + 3 HCl -> HSiCl3 + H2}}

The trichlorosilane is then converted to a mixture of silane and ]:
: {{chem2|4 HSiCl3 -> SiH4 + 3 SiCl4}}
This ] requires a catalyst.

The most commonly used catalysts for this process are ] ], particularly ]. This is referred to as a redistribution reaction, which is a double displacement involving the same central element. It may also be thought of as a ] reaction, even though there is no change in the oxidation number for silicon (Si has a nominal oxidation number IV in all three species). However, the utility of the oxidation number concept for a covalent molecule{{Vague|date={{CURRENTMONTHNAME}} {{CURRENTYEAR}}}}, even a polar covalent molecule, is ambiguous.{{Citation needed|date=December 2022}} The silicon atom could be rationalized as having the highest formal oxidation state and partial positive charge in {{chem2|SiCl4}} and the lowest formal oxidation state in {{chem2|SiH4}}, since Cl is far more electronegative than is H.{{Citation needed|date=December 2022}}

An alternative industrial process for the preparation of very high-purity silane, suitable for use in the production of semiconductor-grade silicon, starts with metallurgical-grade silicon, hydrogen, and ] and involves a complex series of redistribution reactions (producing byproducts that are recycled in the process) and distillations. The reactions are summarized below:

# {{chem2|Si + 2 H2 + 3 SiCl4 -> 4 SiHCl3}}
# {{chem2|2 SiHCl3 -> SiH2Cl2 + SiCl4}}
# {{chem2|2 SiH2Cl2 -> SiHCl3 + SiH3Cl}}
# {{chem2|2 SiH3Cl -> SiH4 + SiH2Cl2}}

The silane produced by this route can be thermally decomposed to produce high-purity silicon and hydrogen in a single pass.

Still other industrial routes to silane involve reduction of ] ({{chem2|SiF4}}) with ] (NaH) or reduction of {{chem2|SiCl4}} with ] ({{chem2|LiAlH4}}).

Another commercial production of silane involves reduction of ] ({{chem2|SiO2}}) under Al and {{chem2|H2}} gas in a mixture of ] and ] ({{chem2|AlCl3}}) at high pressures:<ref>Shriver and Atkins. Inorganic Chemistry (5th edition). W.&nbsp;H. Freeman and Company, New York, 2010, p.&nbsp;358.</ref>

: {{chem2|3 SiO2 + 6 H2 + 4 Al -> 3 SiH4 + 2 Al2O3}}

===Laboratory-scale routes===
In 1857, the German chemists ] and ] discovered silane among the products formed by the action of ] on aluminum silicide, which they had previously prepared. They called the compound ''siliciuretted hydrogen''.<ref>Mellor, J. W. "A Comprehensive Treatise on Inorganic and Theoretical Chemistry", vol.&nbsp;VI, Longmans, Green and Co. (1947), p.&nbsp;216.</ref>

For classroom demonstrations, silane can be produced by heating ] with ] powder to produce ] ({{chem2|Mg2Si}}), then pouring the mixture into hydrochloric acid. The magnesium silicide reacts with the acid to produce silane gas, which ] on contact with air and produces tiny explosions.<ref name="theodoregray">{{cite web |url=https://theodoregray.com/PeriodicTable/PopularScience/2005/10/1/index.html |title=Making Silicon from Sand |url-status=live |archive-url=https://web.archive.org/web/20101129090339/http://theodoregray.com/PeriodicTable/PopularScience/2005/10/1/index.html |work=] |via=Theodore Gray |archive-date=2010-11-29}}.</ref> This may be classified as a ]{{Clarify|date=October 2011}} ] chemical reaction, since the isolated {{chem2|Si(4-)}} ion in the {{chem2|Mg2Si}} structure can serve as a ] capable of accepting four protons. It can be written as

: {{chem2|4 HCl + Mg2Si -> SiH4 + 2 MgCl2}}

In general, the alkaline-earth metals form silicides with the following ]: {{chem2|M^{II}2Si}}, {{chem2|M^{II}Si}}, and {{chem2|M^{II}Si2}}. In all cases, these substances react with Brønsted–Lowry acids to produce some type of hydride of silicon that is dependent on the Si anion connectivity in the silicide. The possible products include {{chem2|SiH4}} and/or higher molecules in the homologous series {{chem2|Si_{''n''}H_{2''n''+2} }}, a polymeric silicon hydride, or a ]. Hence, {{chem2|M^{II}Si}} with their zigzag chains of {{chem2|Si(2-)}} anions (containing two lone pairs of electrons on each Si anion that can accept protons) yield the polymeric hydride {{chem2|(SiH2)_{''x''} }}.

Yet another small-scale route for the production of silane is from the action of ] on ], {{chem2|SiH2Cl2}}, to yield monosilane along with some yellow ] {{chem2|(SiH)_{''x''} }}.<ref>Mellor, J. W. "A Comprehensive Treatise on Inorganic and Theoretical Chemistry", vol.&nbsp;VI. Longmans, Green and Co. (1947), pp.&nbsp;970–971.</ref>

==Properties==
Silane is the ] ] of ]. All four {{chem2|Si\sH}} bonds are equal and their length is 147.98 ].<ref name=cccbdb>{{cite journal | url=https://cccbdb.nist.gov/exp2x.asp?casno=7803625&charge=0 | title=Maintenance | journal=NIST | date=17 October 2019 }}</ref> Because of the greater electronegativity of hydrogen in comparison to silicon, this Si–H bond polarity is the opposite of that in the C–H bonds of methane. One consequence of this reversed polarity is the greater tendency of silane to form complexes with transition metals. A second consequence is that silane is ]&nbsp;— it undergoes spontaneous combustion in air, without the need for external ignition.<ref>{{
cite journal
|author1=Emeléus, H. J. |author2=Stewart, K.
|name-list-style=amp |title = The oxidation of the silicon hydrides
| year = 1935
| journal = Journal of the Chemical Society
| pages = 1182–1189
| doi = 10.1039/JR9350001182}}</ref> However, the difficulties in explaining the available (often contradictory) combustion data are ascribed to the fact that silane itself is stable and that the natural formation of larger silanes during production, as well as the sensitivity of combustion to impurities such as moisture and to the catalytic effects of container surfaces causes its pyrophoricity.<ref>{{
cite journal
| author = Koda, S.
| title = Kinetic Aspects of Oxidation and Combustion of Silane and Related Compounds
| year = 1992
| journal = Progress in Energy and Combustion Science
| volume = 18
| issue = 6
| pages = 513–528
| doi = 10.1016/0360-1285(92)90037-2| bibcode = 1992PECS...18..513K
}}</ref><ref name=timms/> Above {{convert|420|C|F}}, silane decomposes into silicon and ]; it can therefore be used in the ] of silicon.

The Si–H ] is around 384 kJ/mol, which is about 20% weaker than the H–H bond in {{chem2|H2}}. Consequently, compounds containing Si–H bonds are much more reactive than is {{chem2|H2}}. The strength of the Si–H bond is modestly affected by other substituents: the Si–H bond strengths are: {{chem2|SiHF3}} 419 kJ/mol, {{chem2|SiHCl3}} 382 kJ/mol, and SiHMe<sub>3</sub> 398 kJ/mol.<ref>M. A. Brook "Silicon in Organic, Organometallic, and Polymer Chemistry" 2000, J. Wiley, New York. {{ISBN|0-471-19658-4}}.</ref><ref>{{cite web |url=https://www2.chemistry.msu.edu/faculty/reusch/virttxtjml/questions/bndenrgy.htm |title=Standard Bond Energies |publisher=Michigan State University Organic Chemistry}}</ref>

==Applications==
<!-- Please help to remove the usages of the higher silanes -->
]
While diverse applications exist for ], silane itself has one dominant application, as a precursor to elemental silicon, particularly in the semiconductor industry. The higher silanes, such as di- and trisilane, are only of academic interest. About 300 ]s per year of silane were consumed in the late 1990s.{{Update inline|date=November 2023}}<ref name=timms>{{
cite journal
| author = Timms, P. L.
| title = The chemistry of volatile waste from silicon wafer processing
| year = 1999
| journal = Journal of the Chemical Society, Dalton Transactions
| issue = 6
| pages = 815–822
| doi = 10.1039/a806743k}}</ref> Low-cost ] module manufacturing has led to substantial consumption of silane for depositing hydrogenated ] (a-Si:H) on glass and other substrates like metal and plastic. The ] (PECVD) process is relatively inefficient at materials utilization with approximately 85% of the silane being wasted. To reduce that waste and the ] of a-Si:H-based solar cells further several recycling efforts have been developed.<ref>Briend P, Alban B, Chevrel H, Jahan D. American Air, Liquide Inc. (2009) "Method for Recycling Silane (SiH<sub>4</sub>)". , .</ref><ref>{{cite journal |doi=10.1016/j.resconrec.2012.10.002 |title=Life cycle analysis of silane recycling in amorphous silicon-based solar photovoltaic manufacturing |year=2013 |last1=Kreiger |first1=M.A. |last2=Shonnard |first2=D.R. |last3=Pearce |first3=J.M. |journal=Resources, Conservation and Recycling |volume=70 |pages=44–49 |bibcode=2013RCR....70...44K |s2cid=3961031 |url=https://www.academia.edu/2310926 |url-status=live |archive-url=https://web.archive.org/web/20171112225425/http://www.academia.edu/2310926/Life_Cycle_Analysis_of_Silane_Recycling_in_Amorphous_Silicon-Based_Solar_Photovoltaic_Manufacturing |archive-date=2017-11-12}}</ref>

==Safety and precautions==
A number of fatal industrial accidents produced by combustion and detonation of leaked silane in air have been reported.<ref>{{
cite journal
| author = Chen, J. R.
| title = Characteristics of fire and explosion in semiconductor fabrication processes
| year = 2002
| journal = Process Safety Progress
| volume = 21
| issue = 1
| pages = 19–25
| doi = 10.1002/prs.680210106| s2cid = 110162337
}}</ref><ref>{{
cite journal
|author1=Chen, J. R. |author2=Tsai, H. Y. |author3=Chen, S. K. |author4=Pan, H. R. |author5=Hu, S. C. |author6=Shen, C. C. |author7=Kuan, C. M. |author8=Lee, Y. C. |author9=Wu, C. C. |name-list-style=amp |title=Analysis of a silane explosion in a photovoltaic fabrication plant
| year = 2006
| journal = Process Safety Progress
| volume = 25
| issue = 3
| pages = 237–244
| doi = 10.1002/prs.10136|s2cid=111176344 }}</ref><ref>{{
cite journal
|author1=Chang, Y. Y. |author2=Peng, D. J. |author3=Wu, H. C. |author4=Tsaur, C. C. |author5=Shen, C. C. |author6=Tsai, H. Y. |author7=Chen, J. R. |name-list-style=amp |title=Revisiting of a silane explosion in a photovoltaic fabrication plant
| year = 2007
| journal = Process Safety Progress
| volume = 26
| issue = 2
| pages = 155–158
| doi = 10.1002/prs.10194|s2cid=110741985 }}</ref>

Due to weak bonds and hydrogen, silane is a pyrophoric gas (capable of autoignition at temperatures below {{convert|54|°C|°F|disp=or}}).<ref> {{webarchive|url=https://web.archive.org/web/20140519130659/http://www.voltaix.com/images/doc/Mssi000_Silane.pdf |date=2014-05-19}}</ref>
:{{chem2|SiH4 + 2 O2 -> SiO2 + 2 H2O}}{{spaces|5}}<math>\Delta H = -1517 \text{ kJ/mol } = -47.23 \text{ kJ/g}</math>
:{{chem2|SiH4 + O2 -> SiO2 + 2 H2}}
:{{chem2|SiH4 + O2 -> SiH2O + H2O}}
:{{chem2|2 SiH4 + O2 -> 2 SiH2O + 2 H2}}
:{{chem2|SiH2O + O2 -> SiO2 + H2O}}
For lean mixtures a two-stage reaction process has been proposed, which consists of a silane consumption process and a hydrogen oxidation process. The heat of {{chem2|SiO2(s)}} condensation increases the burning velocity due to thermal feedback.<ref>{{
cite journal
| author = V.I Babushok
| title = Numerical Study of Low and High Temperature Silane Combustion
| year = 1998
| journal = The Combustion Institute
| volume = 27
| issue = 2
| pages = 2431–2439
| doi = 10.1016/S0082-0784(98)80095-7
}}</ref>

Diluted silane mixtures with inert gases such as ] or ] are even more likely to ignite when leaked into open air, compared to pure silane: even a 1% mixture of silane in pure nitrogen easily ignites when exposed to air.<ref>{{
cite journal
|author1=Kondo, S. |author2=Tokuhashi, K. |author3=Nagai, H. |author4=Iwasaka, M. |author5=Kaise, M. |name-list-style=amp |title=Spontaneous Ignition Limits of Silane and Phosphine
| year = 1995
| journal = Combustion and Flame
| volume = 101
| issue = 1–2
| pages = 170–174
| doi = 10.1016/0010-2180(94)00175-R|bibcode=1995CoFl..101..170K }}</ref>

In Japan, in order to reduce the danger of silane for amorphous silicon solar cell manufacturing, several companies began to dilute silane with ] gas. This resulted in a symbiotic benefit of making more stable ] cells as it reduced the ].{{citation needed|date=April 2022}}

Unlike methane, silane is fairly toxic: the lethal concentration in air for rats (]) is 0.96% (9,600 ppm) over a 4-hour exposure. In addition, contact with eyes may form ] with resultant irritation.<ref>{{cite web |url=http://www.vngas.com/pdf/g97.pdf |title=MSDS for silane |website=vngas.com |url-status=usurped |archive-url=https://web.archive.org/web/20090220021944/http://www.vngas.com/pdf/g97.pdf |archive-date=2009-02-20}}</ref>

In regards to occupational exposure of silane to workers, the US ] has set a ] of 5 ppm (7&nbsp;mg/m<sup>3</sup>) over an eight-hour time-weighted average.<ref>{{cite web |title=Silicon tetrahydride |work=NIOSH Pocket Guide to Chemical Hazards |publisher=Centers for Disease Control and Prevention |url=https://www.cdc.gov/niosh/npg/npgd0556.html |date=April 4, 2011 |access-date=November 18, 2013 |url-status=live |archive-url=https://web.archive.org/web/20140726044247/http://www.cdc.gov/niosh/npg/npgd0556.html |archive-date=July 26, 2014}}</ref>

==See also==
*] (sometimes called silanes)
*]
*]
*], in which ] (in that compound) and ] (in this compound) are together in the ].

==References==
{{Reflist|30em}}

==Cited sources==
*{{cite book |editor=Haynes, William M. |year=2011 |title=] |edition=92nd |publisher=] |isbn=978-1439855119}}

==External links==
*

{{Silicon compounds}}
{{Molecules detected in outer space}}
{{Hydrides by group}}
{{Authority control}}

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