Triphenylborane

Triphenylborane
IUPAC name

Triphenylborane
Identifiers
CAS number 960-71-4
PubChem 70400
ChemSpider 63579 Y
EC number 213-504-2
Jmol-3D images Image 1
Properties
Molecular formula C18H15B
Molar mass 242.12 g/mol
Appearance White crystals
Melting point

142 °C
Boiling point

203 °C (15 mmHg)
Solubility in water Insoluble
Structure
Molecular shape trigonal planar
Hazards
R-phrases R11
S-phrases S16 S22 S24/25
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Triphenylborane, often abbreviated to BPh3 where Ph is the phenyl group C6H5-, is a chemical compound with the formula B(C6H5)3. It is a white crystalline solid and is both air and moisture sensitive, slowly forming benzene and triphenylboroxine. It is soluble in aromatic solvents.

Contents

Structure and properties

The core of the compound, BC3, has a trigonal planar structure. The phenyl groups are rotated at about a 30° angle from the core plane.[1]

Even though triphenylborane and tris(pentafluorophenyl)boron are structurally similar, their Lewis acidity is not. BPh3 is a weak Lewis acid while B(C6F5)3 is a strong Lewis acid due to the electronegativity of the fluorine atoms. Other boron Lewis acids include BF3 and BCl3.[2]

Synthesis

Triphenylborane was first synthesized in 1922.[3] It is typically made with boron trifluoride diethyl etherate and the Grignard reagent, phenylmagnesium bromide.[4]

BF3•O(C2H5)2 + 3 C6H5MgBr → B(C6H5)3 + 3 MgBrF + (C2H5)2O

Triphenylborane can also be synthesized on a smaller scale by the thermal decomposition of trimethylammonium tetraphenylborate.[5]

[B(C6H5)4][NH(CH3)3] → B(C6H5)3 + N(CH3)3 + C6H6

Applications

Triphenylborane is made commercially by a process developed by Du Pont for use in its hydrocyanation of butadiene to adiponitrile, a nylon intermediate. Du Pont produces triphenylborane by reacting sodium metal, a haloaromatic (chlorobenzene), and a secondary alkyl borate ester.[6]

Triphenylborane can be used to make triarylborane amine complexes, such as pyridine-triphenylborane. Triarylborane amine complexes are used as catalysts for the polymerization of acrylic esters.[6]

References

  1. ^ Zettler, F.; Hausen, H. D.; Hess, H. (1974). "Crystal and Molecular Structure of Triphenylborane". J. Organomet. Chem. 72 (2): 157. doi:10.1016/S0022-328X(00)81488-6. 
  2. ^ Erker, G. (2005). "Tris(pentafluorophenyl)borane: a special boron Lewis acid for special reactions". Dalton Trans. (11): 1883–90. doi:10.1039/b503688g. PMID 15909033. 
  3. ^ E. Krause and R. Nitsche (1922). "Darstellung von organischen Bor-Verbindungen mit Hilfe von Borfluorid, II.: Bortriphenyl und Phenyl-borsäure". Chemische Berichte 55 (5): 1261. doi:10.1002/cber.19220550513. 
  4. ^ R. Köster, P. Binger, and W. Fenzl (1974). "Triphenylborane". Inorg. Synth.. Inorganic Syntheses 15: 134. doi:10.1002/9780470132463.ch30. ISBN 9780470132463. 
  5. ^ G. Wittig, P. Raff (1951). "Ober Komplexbildung mit Triphenyl-bor". Liebigs Annalen der Chemie 573: 195. doi:10.1002/jlac.19515730118. 
  6. ^ a b C. R. Guibert and J. L. Little, “Alkyl- and Arylboranes,” Ullmanns’s Encyclopedia of Industrial Chemistry, Wiley-VCH Verlag, Weinheim, 2005. doi:10.1002/14356007.a04_309