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| Names | |
|---|---|
| Preferred IUPAC name Chlorotri(fluoro)silane | |
| Other names silicon chlorotrifluoride[1] | |
| Identifiers | |
3D model (JSmol) | |
| ChemSpider |
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| |
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| Properties | |
| ClF3Si | |
| Molar mass | 120.53371 |
| Appearance | colorless gas |
| Density | 1.31 g/mL |
| Melting point | −138 °C (−216 °F; 135 K) |
| Boiling point | critical point 303.7 K at 3.46 MPa |
| reacts | |
| Vapor pressure | 16600 |
Refractive index (nD) | 1.279 |
| Structure | |
| distorted tetrahedron | |
| 0.636D(gas) | |
| Related compounds | |
Related compounds | tetrafluorosilane dichlorodifluorosilane |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Chlorotrifluorosilane is an inorganic gaseous compound with formula SiClF3 composed ofsilicon,fluorine andchlorine. It is asilane that substituteshydrogen withfluorine andchlorine atoms.
By heating a mixture of anhydrousaluminium chloride andsodium hexafluorosilicate to between 190 and 250 °C a mixture of gases containing chlorotrifluorosilane is given off. These are condensed at -196 °C degrees and fractionally distilled at temperatures up to -78 °C.[2]
SiClF3 can be made by reactingsilicon tetrachloride andsilicon tetrafluoride gases at 600 °C, producing a mixture of fluorochlorosilanes including about one quarter SiClF3.[3]
SiClF3 can be made by reactingsilicon tetrachloride withantimony trifluoride. Anantimony pentachloride catalyst assists. The products are distilled to separate it out fromtetrafluorosilane anddichlorodifluorosilane.[4][5][6]
At high temperatures above 500 °Csilicon tetrafluoride can react withphosphorus trichloride to yield some SiClF3. This is unusual because SiF4 is very stable.[7]
Silicon tetrachloride can react withtrifluoro(trichloromethyl)silane to yield SiClF3 and CCl3SiCl3.[8]
2-Chloroethyltrifluorosilane or 1,2-dichloroethyltrifluorosilane can be disassociated by an infrared laser to yield SiClF3 and C2H4 (ethylene) orvinyl chloride. By tuning the laser to a vibration frequency of a particular isotope of silicon, differentisotopomers can be selectively broken up in order to have a product that only concentrates one isotope of silicon. So silicon-30 can be increased to 80% by using the 934.5 cm−1 line in aCO2 laser.[9]
The first published preparation of SiClF3 by Schumb and Gamble was by exploding hexafluorodisilane in chlorine: Si2F6 + Cl2 → 2SiClF3. Other products of this explosion may include amorphous silicon, SiCl2F2 and SiF4.[10]
Chlorine reacts withsilicon tetrafluoride in the presence of aluminium chips at 500-600 °C to make mostly silicon tetra chloride and some SiClF3.[11]
Mercuric chloride when heated with SiF3Co(CO)4 breaks the bond to form a 90% yield of SiClF3.[12]
The combination of SiF4 and chlorodimethylphosphine yields some SiClF3.[13]
Trifluorosilane SiHF3 reacts with gaseous chlorine to yield SiClF3 and HCl.[14]
Bond length for Si–Cl is 1.996 Å and for Si–F is 1.558 Å. The bond angle ∠FSiCl = 110.2° and ∠FSiF = 108.7°.[4] The bond length between silicon and chlorine is unusually short, indicating a 31% double bond. This can be explained by the more ionic fluoride bonds withdrawing some charge allowing a partial positive charge on the chlorine.[15]
The molecular dipole moment is 0.636 Debye.[4]
Between 129.18 and 308.83 K the vapour pressure in mm Hg at temperature T in K is given by log10 P = 102.6712 -2541.6/T -43.347 log10 T + 0.071921T -0.000045231 T2.[16]
The heat of formation of chlorotrifluorosilane is -315.0 kcal/mol at 298K.[17]
Chlorotrifluorosilane is hydrolysed by water to produce silica.
Chlorotrifluorosilane reacts with trimethylstannane ((CH3)3SnH) at room temperature to maketrifluorosilane in about 60 hours.[18]
Proposed uses include a dielectric gas with a high breakdown voltage, and lowglobal warming potential, a precursor for making fluorinated silica soot, and a vapour deposition gas.
Chlorotrifluorosilane can form an addition compound withpyridine with formula SiClF3.2py (py=pyridine)[19] An addition compound withtrimethylamine exists.[20][21] This addition compound is made by mixing trimethylamine vapour with Chlorotrifluorosilane and condensing out a solid at -78 °C. If this was allowed to soak in trimethylamine liquid for over eight hours, a diamine complex formed (2Me3N·SiClF3).[21] At 0° the disassociation pressure of the monoamine complex was 23 mm Hg.[21]
SiClF3− is a trigonal bipyramidal shape with a Cl and F atom on the axis. It is formed when gamma rays hit the neutral molecule.[22]
Chlorotetrafluorosilicate (IV) (SiClF4−) can form a stable a pale yellow crystalline compound tetraethylammonium chlorotetrafluorosilicate.[23]
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