Activation of C-H and C-F bonds by cyclopentadienyl iridium complexes

Abstract

Photochemical C-H activation of cycloalkanes by aminoethyl-functionalised cyclopentadienyl iridium complexes [Cp^Ir(CO)2 and Cp*^Ir(CO)2] proceeded in a broadly similar way to their unfunctionalised analogues to yield hydridoalkyl iridium complexes CpxIr(CO)(R)(H) (x = Cp^, Cp*^). In addition, their corresponding dihydride species CpxIr(CO)(H)2 were also obtained. Under a carbon monoxide atmosphere, carbonylation of the activated cyclohexyl species occurred to produce cyclohexanecarboxaldehyde. In situ infrared spectroscopic studies with the help of BTEM deconvolution on the data collected allowed for the identification of several species present in low concentration in the reaction mixture.Cp*Ir(CO)2, 2a reacted with hexafluorobenzene under photoirradiation to afford Cp*Ir(CO)(N72-C6F6) and [Cp*Ir(C6F5)(o --CO)]2. The reaction of 2a with fluoroarenes carrying an electron-withdrawing group in the presence of water at ambient temperature gave metallocarboxylic acids with the general formula Cp*Ir(CO)(COOH)(p-C6F4X). The reaction is proposed to occur via a nucleophilic substitution pathway.