Tris(pentafluorophenyl)boron
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Tris(pentafluorphenyl)boron | |
---|---|
General | |
Systematic name | Tris(pentafluorophenyl)boron |
Other names | Perfluorotriphenylboron |
Molecular formula | (C6F5)3B C18F15B |
SMILES | ? |
Molar mass | 511.98 g/mol |
Appearance | colorless solid |
CAS number | [1109-15-5] |
Properties | |
Density and phase | ? g/cm3, ? |
Solubility in water | forms adduct |
Melting point | 126-131 °C |
Boiling point | ? °C (? K) |
Viscosity | ? cP at ? °C |
Structure | |
Molecular shape | trigonal planar |
Dipole moment | 0 D |
Hazards | |
MSDS | External MSDS |
Main hazards | ? |
NFPA 704 | |
R/S statement | R: 36/37/38 S: 26-36 |
RTECS number | ? |
Supplementary data page | |
Structure and properties |
n, εr, etc. |
Thermodynamic data |
Phase behaviour Solid, liquid, gas |
Spectral data | UV, IR, NMR, MS |
Related compounds | |
Related compounds | Triphenylboron (C6H5)3B BF3 |
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references |
Tris(pentafluorophenyl)boron is the chemical compound (C6F5)3B. The molecule consists of three pentafluorophenyl groups attached in a "paddle-wheel" manner to a central boron atom; the BC3 core is planar. It has been described as the “ideal Lewis acid” because of its versatility and the relative inertness of the B-C bonds. Related fluoro-substituted boron compounds, such as those containing B-CF3 groups, decompose with formation of B-F bonds.
Contents |
[edit] Preparation
(C6F5)3B is prepared using a Grignard reagent:
- 3C6F5MgBr + BCl3 → (C6F5)3B + 3MgBrCl
Originally the synthesis employed C6F5Li, but this reagent can detonate with elimination of LiF.[1]
[edit] Lewis acidity
The most noteworthy property of this molecule is its strong Lewis acidity: stronger than BF3 but weaker than BCl3. This property indicates that the electronegativity of the C6F5 group and a halide are similar. An most important application of (C6F5)3B is that it forms noncoordinating anions by removing anionic ligands from metal centers.[2] Illustrative is a reaction that give rise to alkene polymerization catalyst:
- (C6F5)3B + (C5H5)2Zr(CH3)2 → [(C5H5)2ZrCH3+][ C6F5)3BCH3−]
In this process, the strongly coordinating methyl group transfers to the boron to expose a reactive site on zirconium. Alkenes can bind to this site, whereupon they couple to the remaining methyl ligand to give a propyl ligand, thereby starting the growth of a chain of polyethylene.
(C6F5)3B is also capable of abstracting hydride to give [(C6F5)3BH]−, and it catalyzes hydrosilylation of aldehydes. Otherwise (C6F5)3B binds to a wide range of Lewis bases, even weak ones.[3] The compound is hygroscopic, forming the trihydrate [(C6F5)3BOH2](H2O)2, wherein one water in coordinated to boron and the other two waters are hydrogen-bonded to the coordinated water.
[edit] Other reactions
(C6F5)3B was used to prepare a compound containing a Xe-C bond:
- (C6F5)3B + XeF2 → [C6F5Xe+][(C6F5)2BF2−]
[edit] Related compounds
Chivers, T. “Pentafluorophenylboron halides: 40 years later” Journal of Fluorine Chemistry (2002), volume 115, page 1-8.
[edit] References
- ^ Piers, W. E.; Chivers, T. “Pentafluorophenylboranes: from Obscurity to Applications” Chemical Society Reviews volume 26, pages 345-354 (1997)
- ^ Fuhrmann, H.; Brenner, S.; Arndt, P.; Kempe, R. “Octahedral Group 4 Metal Complexes That Contain Amine, Amido, and Aminopyridinato Ligands: Synthesis, Structure, and Application in α-Olefin Oligo- and Polymerization” Inorganic Chemistry 1996, 35, 6742-6745.
- ^ Erker, G. "Tris(pentafluorophenyl)borane: A Special Boron Lewis Acid for Special Reactions" Dalton Transactions (2005), 1883-1890.