Pentafluorophenyl Cold Complexes

The first thing to point out is that the use of a pentafluorophenyl CgFs group with late transition metal confers on the complexes great stability, both thermodynamic and kinetic. This general fact, that is also true in gold chemistry, can be explained by different factors  

The strong electron-withdravhng effect of the CeFs group that is estimated to have a Hammett constant ap of 0.4 [16,17] and a Brown constant of 0.99 [18,19]. The 

Lewis acid strength of B(C6F5)3 is between BF3 and BCI3 which means that the electron-withdrawing effect of the C Fs group should be comparable with that of these two halogens [20]. 

Unlike alkyl-gold bonds the Au—C bonds in pentafluorophenyl compounds are more resistant to cleavage by protic acids, giving more chemical integrity to the complexes. 

The pentafluorophenyl group imparts greater crystallinity to the complexes and as a result many complexes have been studied by X-ray crystallography. Although vith other metal centers C Fs-CaFs or CfiFs-CfiHs n-n stacking interactions are observed [21, 22], there are not many examples in gold chemistry and they have been sho vn very recently [23]. 

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