Trichlorosilane

Trichlorosilane is an inorganic compound with the formula HCl3Si. It is a colourless, volatile liquid. Purified trichlorosilane is the principal precursor to ultrapure silicon in the semiconductor industry. In water, it rapidly decomposes to produce a siloxane polymer while giving off hydrochloric acid. Because of its reactivity and wide availability, it is frequently used in the synthesis of silicon-containing organic compounds.[2]

Trichlorosilane
Names
IUPAC name
trichlorosilane
Other names
silyl trichloride, silicochloroform
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.030.026
EC Number
  • 233-042-5
RTECS number
  • VV5950000
UNII
UN number 1295
  • InChI=1S/Cl3HSi/c1-4(2)3/h4H checkY
    Key: ZDHXKXAHOVTTAH-UHFFFAOYSA-N checkY
  • InChI=1/Cl3HSi/c1-4(2)3/h4H
    Key: ZDHXKXAHOVTTAH-UHFFFAOYAH
  • Cl[SiH](Cl)Cl
Properties
HCl3Si
Molar mass 135.45 g/mol
Appearance colourless liquid
Density 1.342 g/cm3
Melting point −126.6 °C (−195.9 °F; 146.6 K)
Boiling point 31.8 °C (89.2 °F; 304.9 K)
hydrolysis
Hazards[1]
GHS labelling:
GHS02: FlammableGHS05: CorrosiveGHS06: ToxicGHS07: Exclamation mark
Danger
H224, H250, H302, H314, H332
P231, P280, P305+P351+P338+P310, P310, P370+P378
NFPA 704 (fire diamond)
NFPA 704 four-colored diamond
3
4
2
W
Flash point −27 °C (−17 °F; 246 K)
185 °C (365 °F; 458 K)
Explosive limits 1.2–90.5%
Safety data sheet (SDS) ICSC 0591
Related compounds
Related chlorosilanes
 Chlorosilane
Dichlorosilane
Dichloromethylsilane
Chlorodimethylsilane
Silicon tetrachloride
Related compounds
 Trifluorosilane
Tribromosilane
Chloroform
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Production

Trichlorosilane is produced by treating powdered metallurgical grade silicon with blowing hydrogen chloride at 300 °C. Hydrogen is also produced, as described in the chemical equation:

Si + 3 HCl → HCl3Si + H2

Yields of 80-90% can be achieved. The main byproducts are silicon tetrachloride (chemical formula SiCl4), hexachlorodisilane (Si2Cl6) and dichlorosilane (H2SiCl2), from which trichlorosilane can be separated by distillation.

Tank car of trichlorosilane. UN number: 2988 (Chlorosilanes). ADR hazard identification number: X338 (Highly flammable liquid, corrosive, which reacts dangerously with water)

It is also produced from silicon tetrachloride:[3]

Si + 3 SiCl4 + 2 H2 → 4 HCl3Si

Applications

Trichlorosilane is the basic ingredient used in the production of purified polysilicon.

HCl3Si → Si + HCl + Cl2

Ingredient in hydrosilylation

Via hydrosilylation, trichlorosilane is a precursor to other useful organosilicon compounds:

RCH=CH2 + HSiCl3 → RCH2CH2SiCl3

Some useful products of this or similar reactions include octadecyltrichlorosilane (OTS), perfluoroctyltrichlorosilane (PFOTCS), and perfluorodecyltrichlorosilane (FDTS). These reagents used in surface science and nanotechnology to form Self-assembled monolayers. Such layers containing fluorine decrease surface energy and reduce sticking. This effect is usually exploited as coating for MEMS and microfabricated stamps for a nanoimprint lithography (NIL) and in injection molding tools.[4]

Organic synthesis

Trichlorosilane is a reagent in the conversion of benzoic acids to toluene derivatives. In the first step of a two-pot reaction, the carboxylic acid is first converted to the trichlosilylbenzyl compound. In the second step, the benzylic silyl derivative is converted to the toluene derivative with base.[5]

Safety

Trichlorosilane is highly reactive, and may respond violently (and even explosively) to many compounds.[6] This also includes water, potentially producing silicon dioxide, chlorine, hydrogen, hydrogen chloride (and it's aqueous form hydrochloric acid), and heat. Trichlorosilane can cause hazardous chemical reactions with moisture and humidity alone, and should be handled and stored under inert gas.[6] Spills of trichlorosilane may be neutralized using a 1-1 ratio of sodium hydroxide, or a 2-1 ratio of sodium bicarbonate to trichlorosilane.[7] Fires can be extinguished using alcohol-resistant aqueous film-forming foam (AR-AFFF).[6][7]

References
  1. "GESTIS-Stoffdatenbank". gestis.dguv.de.
  2. Lianhong Xu, Ravi Kurukulasuriya, "Trichlorosilane" Encyclopedia of Reagents for Organic Synthesis, 2006. doi:10.1002/047084289X.rt213.pub2
  3. Simmler, W. "Silicon Compounds, Inorganic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a24_001.
  4. Cech J, Taboryski R (2012). "Stability of FDTS monolayer coating on aluminum injection molding tools". Applied Surface Science. 259: 538–541. Bibcode:2012ApSS..259..538C. doi:10.1016/j.apsusc.2012.07.078.
  5. George S. Li, David F. Ehler, R. A. Benkeser "Methyl Groups By Reduction Of Aromatic Carboxylic Acids With Trichlorosilane - Tri-n-propylamine: 2-methylbiphenyl" Org. Synth. 1977, volume 56, pp. 83. doi:10.15227/orgsyn.056.0083
  6. Trichlorosilane: Safety Data Sheet P-4823 (PDF) (Report). Linde Inc. February 3, 2022. Archived from the original (PDF) on June 6, 2022.
  7. Hazardous Substance Fact Sheet: Trichlorosilane (PDF) (Report). New jersey department of health. October 2010.
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