Perfluoroaryl Boranes in the Synthesis of Novel Weakly Coordinating Anions

Perfluoroaryl Boranes in the Synthesis of Novel Weakly Coordinating Anions 

Perfluoroarylborates are among the most WCAs known, and are certainly the most easily accessible and widely available. As such, they have been applied to numerous 

The effectiveness of these anions depends to a large degree on the integrity of the jl-X linkage. The p,-NH2 compound is air and moisture stable and exhibits a particularly strong bridge, possibly by virtue of four N-H- F hydrogen bonds between ortho fluorine atoms and the amido NH protons. Activation of common metallocenes with the trityl salt 

Bochmann has also produced a novel class of large dianionic borates XV based on the non-labile fefra-cyano Ni and Pd(II) metallates [K12 M(CN) i 2. 215a The metals in these WCAs are strictly square planar and as such the anion assumes a flat rather than spherical shape, with a torus of fluorination on the periphery of the plane. The bis-trityl salts of these dianions afford catalysts that are not as productive as those formed from the XIV class (X = CN), although they are still much more active than borane activated catalysts. The lower activity was attributed to the inherently greater cation/anion attraction in a monocation/dianion pair. 

All of these species (XIV, XV) have been for the most part applied towards function in the olefin polymerization arena use of these novel anions for the stabilization of other electrophilic species remains to be explored. Recently, the imidazolide anion XVI, as well as the perfluorinated tetraaryl borate derived from the diborane IX of Chart 2, have been used to stabilize iodonium cations.222 These cations are used as photoinitiators for cationic polymerization of epoxy resins in photolithography applications. While use of the [B(C6F5)4] led to a breakthrough in this area of research,223 higher activities are observed for more WCAs. 

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