Intimate relationship between C-I reductive elimination, aryl scrambling and isomerization processes in Au(III) complexes.

19 F NMR monitoring shows that heating trans -[Au III Rf 2 I 2 ] - solutions (Rf = C 6 F 3 Cl 2 -3,5) leads to formation of cis -[AuRf 2 I 2 ] - , [AuRf 3 I] - and [AuRfI 3 ] - via kinetic competition between isomerization and Rf/I scrambling. The system evolution is driven by the easy Rf-I reductive elimination from [AuRfI 3 ] - (forming also [AuI 2 ] - ), which is faster than any of the Rf-Rf couplings from the coexisting species, hindering the commonly desired and thermodynamically preferred C-C coupling. A kinetic model where I - dissociation triggers both isomerization and transmetalation steps is proposed, which fits well the experimental data. DFT calculations support that the lower bond strength of Au III -I compared to other halides produces a pathway switch that makes C-I coupling kinetically preferred. Consequently, it is better avoided in reactions looking for C-C coupling.