Imidazolium bisimidazolium salts

The C2 - H oxidative addition of imidazolium salts to metal complexes was recently proved for metals other than low valent group 10. The reaction of a ferrocenyl-bisimidazolium salt to [IrCl(cod)]2 in the presence of NEt3 provided the first evidence of the preparation of a stable NHC-Ir(III)-H complex by direct oxidative addition of the imidazolium salt [96]. It was proposed that the ferrocenyl fragment may be sterically protecting the M - H from further reductive elimination, but later it was shown that this fragment was not necessary in order to obtain the desired NHC-Ir(III)-H complexes (Scheme 43) [159]. The role of the weak base (NEt3 in this case) had to be reconsidered in order to explain the overall metallation process, and it was proposed that a mechanism as that shown in Scheme 44 may better explain the process. The oxidative addition of the C2 - H bond of the imida-... 

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