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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.
(C6F5)3B is prepared using a Grignard reagent:
Originally the synthesis employed C6F5Li, but this reagent can detonate with elimination of LiF.
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. Illustrative is a reaction that give rise to alkene polymerization catalyst:
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. 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.
Related compounds are Pentafluorophenylboron halides. 
(C6F5)3B was used to prepare a compound containing a Xe-C bond:
The bulky mesityl groups prevent the phosphorus atom from coordinating directly to boron and instead the ring is attacked. When the fluorine atom on boron is replaced by hydrogen with dimethylchlorosilylhydride, the resulting phosphazenium borate is capable of reversible hydrogen storage 
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Tris(pentafluorophenyl)boron". A list of authors is available in Wikipedia.|