Anionic Derivatives of Perfluorinated Trimethylgold

The homoleptic compound [PPh₄ ][CF₃ AuCF₃ ] cleanly undergoes photoinduced oxidative addition of CF₃ I to afford the organogold(III) derivative [PPh₄ ][(CF₃ )₃ AuI] in good yield and under mild conditions. This compound provides a convenient entry to the chemistry of the perfluorinated (CF₃ )₃ Au fragment, the properties of which were analyzed with the aid of DFT methods and compared with those of the homologous non-fluorinated (CH₃ )₃ Au moiety. It was found that reductive elimination of CX₃ -CX₃ in the former (X=F) requires a much higher energy barrier than in the latter (X=H) and is therefore considerably less favored. This can be considered as one of the main features underlying the significantly higher stability associated to the (CF₃ )₃ Au fragment and its derivatives. This unsaturated, 14-electron species can be stabilized by coordination of any of the halide ligands, including fluoride. In fact, the whole series of anionic [PPh₄ ][(CF₃ )₃ AuX] complexes (X=F, Cl, Br, I, CN) has now been isolated and conveniently characterized. Evidence for intermolecular decomposition pathways upon thermolysis in the condensed phase is presented.