- Boron trichloride
Chembox new
Name = Boron trichloride
ImageFile = Boron-trichloride-2D.png
ImageName = Boron trichloride
ImageFile1 = Boron-trichloride-3D-vdW.png
ImageName1 = Boron trichloride
IUPACName = Boron trichloride
OtherNames = Boron(III) chloride
Section1 = Chembox Identifiers
CASNo = 10294-34-5
RTECS = ED1925000
Section2 = Chembox Properties
Formula = BCl3
MolarMass = 117.17 g/mol
Appearance = Colorless gas,
fumes in air
Density = 1.43 g/ml (O °C)
Solubility = "decomp."
MeltingPt = −107.3 °C
BoilingPt = 12.5 °C
Section3 = Chembox Structure
MolShape = Trigonal planar ("D"3h)
Dipole = zero
Section7 = Chembox Hazards
ExternalMSDS =
EUClass = Very toxic (T+)
RPhrases = R14, R26/28, R34
SPhrases = S1/2, S9, S26, S28,
S36/37/39, S45
FlashPt = Non-flammable
Section8 = Chembox Related
OtherAnions =Boron trifluoride Boron tribromide Boron triiodide
OtherCations =Aluminium chloride Gallium chloride
OtherCpds =Boron oxide Carbon tetrachloride Boron trichloride is a
chemical compound with the formula BCl3. This colorless gas is a valuable reagent inorganic synthesis . It is also dangerously reactive.Production and properties
Boron reacts with
halogens to give the corresponding trihalides. Boron trichloride is, however, produced industrially by directchlorination ofboron oxide andcarbon at 500 °C.:B2O3 + 3 C + 3 Cl2 → 2 BCl3 + 3 COThe synthesis is analogous to theKroll process for the conversion of titanium dioxide to titanium tetrachloride. In the laboratory BF3 reacted with AlCl3 gives BCl3 via halogen exchange.Greenwood&Earnshaw] BCl3 is a trigonal planar molecule like the other boron trihalides, and has a bond length of 175pm. It has a zero dipole moment because it is symmetric and therefore the dipole moments associated with the bonds cancel each other out. Boron trichloride does not form dimers, although there is some evidence that may indicate dimerisation at very low temperatures (20°K). NMR studies of mixtures of boron trihalides shows the presence of mixed halides which may indicate a four centre intermediate e.g. a dimer. The absence of dimerisation contrasts with the other trihalides of group 13 which contain 4 or 6 coordinate metal centres, for example see AlCl3 and GaCl3. A degree of π-bonding has been proposed to explain the short B− Cl distance although there is some debate as to its extent.BCl3 is a
Lewis acid readily formingadduct s with tertiaryamines ,phosphines ,ethers ,thioether s, andhalide ions. [cite journal| author = W. Gerrard and M. F. Lappert| title = Reactions Of Boron richloride With Organic Compounds| journal =Chemical Reviews | year = 1958| volume = 58| pages = 1081–1111| doi = 0.1021/cr50024a003] For example, BCl3S(CH3)2 (CAS# 5523-19-3) is often employed as a conveniently handled source of BCl3 because this solid (m.p. 88-90 °C) releases BCl3::(CH3)2SBCl3overrightarrow{leftarrow} (CH3)2S + BCl3When boron trichloride is passed at low pressure through devices delivering an electric discharge, diboron tetrachloride, [Wartik, T.; Rosenberg, R.; Fox, W. B. "Diboron tetrachloride" Inorganic Syntheses 1967, volume X, pages 118-126.] Cl2B-BCl2, and tetraboron tetrachloride, formula B4Cl4, are formed. Colourless diboron tetrachloride (m.p. -93 °C) has a planar molecule in the solid, (similar to
dinitrogen tetroxide , but in the gas phase the structure is staggered. It decomposes at room temperatures to give a series of monochlorides having the general formula (BCl)"n", in which "n" may be 8, 9, 10, or 11; the compounds with formulas B8Cl8 and B9Cl9 are known to contain closed cages of boron atoms.The mixed
aryl andalkyl boron chlorides are also of interest.Phenyl boron dichloride is commercially available. Such species can be prepare by the reaction of BCl3 with organotin reagents::2 BCl3 + R4Sn → 2 RBCl2 + R2SnCl2Uses
Boron trichloride is a starting material for the production of elemental boron. It is also used in the
refining ofaluminium ,magnesium ,zinc , andcopper alloys to removenitrides ,carbide s, andoxides from molten metal. It has been used as a soldering flux for alloys of aluminium,iron , zinc,tungsten , andmonel . Aluminum castings can be improved by treating the melt with boron trichloride vapors. In the manufacture of electrical resistors, a uniform and lasting adhesivecarbon film can be put over aceramic base using BCl3. It has been used in the field of high energy fuels and rocket propellants as a source of boron to raise BTU value. BCl3 is also used inplasma etching insemiconductor manufacturing. This gas etches metal oxides by formation of a volatile BOClx compounds.BCl3 is used as a
reagent in the synthesis of organic compounds. Like the corresponding bromide, it cleaves C-O bonds inether s. [Yamamoto, Y.; Miyaura, N. "Boron Trichloride" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. DOI: 10.1002/047084289.]afety
BCl3 is an aggressive reagent that releases
hydrogen chloride upon exposure to moisture oralcohol s. Thedimethyl sulfide adduct is safer to use, when possible.References
*cite journal
author = D. R. Martin
title = Coordination compounds of boron trichloride. I - A review
journal =Chemical Reviews
year = 1944
volume = 34
pages = 461–473
doi = 10.1021/cr60109a005
* cite journal
author = Kabalka GW, Wu ZZ, Ju YH
title = The use of organoboron chlorides and bromides in organic synthesis
journal = Journal of Organometallic Chemistry
year = 2003
volume = 680
pages = 12–22
doi = 10.1016/S0022-328X(03)00209-2External links
*
Wikimedia Foundation. 2010.