Difluorosilane

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Difluorosilane
Difluorsilan.svg
Difluorosilane-elpot-transparent-3D-balls.png
Difluorosilane-3D-vdW.png
Identifiers
3D model (JSmol)
ChemSpider
PubChem CID
  • InChI=1S/F2H2Si/c1-3-2/h3H2
    Key: PUUOOWSPWTVMDS-UHFFFAOYSA-N
  • F[SiH2]F
Properties
F2H2Si
Molar mass 68.098 g·mol−1
Appearancecolourless gas
Melting point −122 °C (−188 °F; 151 K)
Boiling point −77.8 °C (−108.0 °F; 195.3 K)
Thermochemistry [1]
262.12 J/mol•K
-790.78 kJ/mol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Difluorosilane is a gaseous chemical compound with formula SiH2F2. It can be considered as a derivative of silane with two hydrogen atoms replaced with fluorine.

Contents

Production

Difluorosilane can be made by fluorinating dichlorosilane with antimony trifluoride. [2] [3]

3 SiH2Cl2 + 2 SbF3 → 3 SiH2F2 + 2 SbCl3

Some is also made in a reaction of silicon tetrafluoride with hydrogen

SiF4 + 2 H2 → SiH2F2 + 2 HF

Traces of difluorosilane are made when coal is burnt. [4]

Properties

Difluorosilane is a gas with boiling point −77.8 °C, and a freezing point of −122 °C. It has no colour. The silicon–fluorine bond length in difluorosilane is 1.358 Å which is greater than that in fluorosilane but less than the length in trifluorosilane. [5]

Reactions

In an electric discharge, hydrogen atoms are preferentially removed from the molecule and SiHF2SiHF2 is formed along with hydrogen. [3]

2 SiH2F2SiHF2SiHF2 + H2

At elevated temperatures, difluorosilane can disproportionate by swapping hydrogen and fluorine atoms between molecules to form fluorosilane and trifluorosilane. [5]

Use

Difluorosilane is used in dental varnish in order to prevent tooth cavities. [6]

Difluorosilane is also used in chemical vapour deposition to deposit silicon nitride films.

Related Research Articles

Silane is an inorganic compound with chemical formula, SiH4. It is a colourless, pyrophoric, toxic gas with a sharp, repulsive smell, somewhat similar to that of acetic acid. Silane is of practical interest as a precursor to elemental silicon. Silane with alkyl groups are effective water repellents for mineral surfaces such as concrete and masonry. Silanes with both organic and inorganic attachments are used as coupling agents.

Hydrofluoric acid Solution of hydrogen fluoride in water

Hydrofluoric acid is a solution of hydrogen fluoride (HF) in water. Solutions of HF are colourless, acidic and highly corrosive. It is used to make most fluorine-containing compounds; examples include the commonly used pharmaceutical antidepressant medication fluoxetine (Prozac) and the material PTFE (Teflon). Elemental fluorine is produced from it. It is commonly used to etch glass and silicon wafers.

Noble gas compounds are chemical compounds that include an element from the noble gases, group 18 of the periodic table. Although the noble gases are generally unreactive elements, many such compounds have been observed, particularly involving the element xenon. From the standpoint of chemistry, the noble gases may be divided into two groups: the relatively reactive krypton, xenon (12.1 eV), and radon (10.7 eV) on one side, and the very unreactive argon (15.8 eV), neon (21.6 eV), and helium (24.6 eV) on the other. Consistent with this classification, Kr, Xe, and Rn form compounds that can be isolated in bulk at or near standard temperature and pressure, whereas He, Ne, Ar have been observed to form true chemical bonds using spectroscopic techniques, but only when frozen into a noble gas matrix at temperatures of 40 K or lower, in supersonic jets of noble gas, or under extremely high pressures with metals.

Tungsten(VI) fluoride, also known as tungsten hexafluoride, is an inorganic compound with the formula WF6. It is a toxic, corrosive, colorless gas, with a density of about 13 grams per litre (0.00047 lb/cu in) (roughly 11 times heavier than air.) It is one of the densest known gases under standard conditions. WF6 is commonly used by the semiconductor industry to form tungsten films, through the process of chemical vapor deposition. This layer is used in a low-resistivity metallic "interconnect". It is one of seventeen known binary hexafluorides.

In chemistry, a hypervalent molecule is a molecule that contains one or more main group elements apparently bearing more than eight electrons in their valence shells. Phosphorus pentachloride, sulfur hexafluoride, chlorine trifluoride, the chlorite ion, and the triiodide ion are examples of hypervalent molecules.

In chemistry, an interhalogen compound is a molecule which contains two or more different halogen atoms and no atoms of elements from any other group.

Hydrogen fluoride Chemical compound

Hydrogen fluoride (fluorane) is an inorganic compound with the chemical formula HF. This colorless gas or liquid is the principal industrial source of fluorine, often as an aqueous solution called hydrofluoric acid. It is an important feedstock in the preparation of many important compounds including pharmaceuticals and polymers, e.g. polytetrafluoroethylene (PTFE). HF is widely used in the petrochemical industry as a component of superacids. Hydrogen fluoride boils at near room temperature, much higher than other hydrogen halides.

Hexafluorosilicic acid Octahedric silicon compound

Hexafluorosilicic acid is an inorganic compound with the chemical formula H
2
SiF
6
. Although no evidence has been presented for the existence of this species in solution or as a solid, aqueous solutions of hexafluorosilicic acid are well-defined, consisting of salts derived from various protonated forms of water as the cation and hexafluorosilicate as the anion. These salts and their aqueous solutions are colorless.

Xenon difluoride Chemical compound

Xenon difluoride is a powerful fluorinating agent with the chemical formula XeF
2
, and one of the most stable xenon compounds. Like most covalent inorganic fluorides it is moisture-sensitive. It decomposes on contact with water vapor, but is otherwise stable in storage. Xenon difluoride is a dense, colourless crystalline solid.

Sulfur tetrafluoride Chemical compound

Sulfur tetrafluoride is the chemical compound with the formula SF4. It is a colorless corrosive gas that releases dangerous HF upon exposure to water or moisture. Despite these unwelcome characteristics, this compound is a useful reagent for the preparation of organofluorine compounds, some of which are important in the pharmaceutical and specialty chemical industries.

Antimony trifluoride is the inorganic compound with the formula SbF3. Sometimes called Swarts' reagent, is one of two principal fluorides of antimony, the other being SbF5. It appears as a white solid. As well as some industrial applications, it is used as a reagent in inorganic and organofluorine chemistry.

Dioxygenyl Chemical compound

The dioxygenyl ion, O+
2
, is a rarely-encountered oxycation in which both oxygen atoms have a formal oxidation state of +1/2. It is formally derived from oxygen by the removal of an electron:

Tetrafluoroammonium

The tetrafluoroammonium cation is a positively charged polyatomic ion with chemical formula NF+
4
. It is equivalent to the ammonium ion where the hydrogen atoms surrounding the central nitrogen atom have been replaced by fluorine. Tetrafluoroammonium ion is isoelectronic with tetrafluoromethane CF
4
, trifluoramine oxide ONF
3
and the tetrafluoroborate BF
4
anion.

Thiophosphoryl fluoride Chemical compound

Thiophosphoryl fluoride is an inorganic molecular gas with formula PSF3 containing phosphorus, sulfur and fluorine. It spontaneously ignites in air and burns with a cool flame. The discoverers were able to have flames around their hands without discomfort, and called it "probably one of the coldest flames known". The gas was discovered in 1888.

Nitrogen pentafluoride (NF5) is a theoretical compound of nitrogen and fluorine that is hypothesized to exist based on the existence of the pentafluorides of the atoms below nitrogen in the periodic table, such as phosphorus pentafluoride. Theoretical models of the nitrogen pentafluoride molecule are either a trigonal bipyramidal covalently bound molecule with symmetry group D3h, or NF+
4
F, which would be an ionic solid.

Fluorine forms a great variety of chemical compounds, within which it always adopts an oxidation state of −1. With other atoms, fluorine forms either polar covalent bonds or ionic bonds. Most frequently, covalent bonds involving fluorine atoms are single bonds, although at least two examples of a higher order bond exist. Fluoride may act as a bridging ligand between two metals in some complex molecules. Molecules containing fluorine may also exhibit hydrogen bonding. Fluorine's chemistry includes inorganic compounds formed with hydrogen, metals, nonmetals, and even noble gases; as well as a diverse set of organic compounds. For many elements the highest known oxidation state can be achieved in a fluoride. For some elements this is achieved exclusively in a fluoride, for others exclusively in an oxide; and for still others the highest oxidation states of oxides and fluorides are always equal.

Trifluorosilane Chemical compound

Trifluorosilane (silicon trifluoride) is the chemical compound with the formula F3HSi. At standard temperature and pressure, trifluorosilane is a colorless gas. Note that the free radical F3Si is often also referred to as trifluorosilane.

Pauling's principle of electroneutrality states that each atom in a stable substance has a charge close to zero. It was formulated by Linus Pauling in 1948 and later revised. The principle has been used to predict which of a set of molecular resonance structures would be the most significant, to explain the stability of inorganic complexes and to explain the existence of π-bonding in compounds and polyatomic anions containing silicon, phosphorus or sulfur bonded to oxygen; it is still invoked in the context of coordination complexes. However, modern computational techniques indicate many stable compounds have a greater charge distribution than the principle predicts.

Chlorotrifluorosilane is an inorganic gaseous compound with formula SiClF3 composed of silicon, fluorine and chlorine. It is a silane that substitutes hydrogen with fluorine and chlorine atoms.

Chlorine trifluoride oxide Chemical compound

Chlorine oxide trifluoride or chlorine trifluoride oxide is a corrosive liquid molecular compound with formula ClOF3. It was developed secretly as a rocket fuel oxidiser.

References

  1. Chase, M. W. (1998). "NIST-JANAF Themochemical Tables, Fourth Edition": 1–1951.{{cite journal}}: Cite journal requires |journal= (help)
  2. 郝润蓉 等. 无机化学丛书 第三卷 碳 硅 锗分族. 科学出版社, 1998. pp 178. 2.3 卤代硅烷
  3. 1 2 Addison, C. C. (1973). Inorganic Chemistry of the Main-Group Elements. Royal Society of Chemistry. p. 188. ISBN   9780851867526.
  4. Kruszewski, Łukasz; Fabiańska, Monika J.; Ciesielczuk, Justyna; Segit, Tomasz; Orłowski, Ryszard; Motyliński, Rafał; Kusy, Danuta; Moszumańska, Izabela (November 2018). "First multi-tool exploration of a gas-condensate-pyrolysate system from the environment of burning coal mine heaps: An in situ FTIR and laboratory GC and PXRD study based on Upper Silesian materials". Science of the Total Environment. 640–641: 1044–1071. Bibcode:2018ScTEn.640.1044K. doi:10.1016/j.scitotenv.2018.05.319. PMID   30021271. S2CID   51703425.
  5. 1 2 Ebsworth, E. A. V. (2013). Volatile Silicon Compounds: International Series of Monographs on Inorganic Chemistry. Elsevier. pp. 54–56. ISBN   9781483180557.
  6. Brambilla, Eugenio (2001). "Fluoride – Is It Capable of Fighting Old and New Dental Diseases?". Caries Research. 35 (1): 6–9. doi:10.1159/000049101. PMID   11359049. S2CID   24969435.