Activation of C–H and H–H bonds by dinuclear iridium complexes. Oxidative addition to highly active unsaturated 32e− diiridium species

Reactions of [(Cp∗Ir)2(μ-dmpm)(μ-H)2][OTf]2 (1) with NaOtBu in aromatic solvent at room temperature give [(Cp∗Ir)(H)(μ-dmpm)(μ-H)(Cp∗Ir)(Ar)][OTf] [Ar = Ph (3), p-Tol (4a), m-Tol (4b), 2-furyl (5a), 3-furyl (5b)] via intermolecular aromatic C–H activation. Treatment of [(Cp∗Ir)2(μ-dppm)(μ-H)2][OTf]2 (2) with weak base (Et2NH) results in intramolecular C–H activation of a phenyl group in the dppm ligand to give [(Cp∗Ir)(H){μ-PPh(C6H4)CH2PPh2}(μ-H)(Cp∗Ir)][OTf] (6). Reaction of 1 with NaOtBu in tetrahydrofuran under H2 (1 atm) results in activation of the H–H bond to give [{(Cp∗Ir)(H)}2(μ-dmpm)(μ-H)][OTf] (7). Reaction of 1 with NaOtBu in dichloromethane under carbon monoxide (1 atm) gives a carbonyl-bridged IrII–IrII complex, [(Cp∗Ir)2(μ-dmpm)(μ-H)(μ-CO)][OTf] (8-OTf). These results strongly suggest that the active species in C–H and H–H bond activation starting with 1 and 2 would be unsaturated 32e− diiridium species. The structures of 3, 5a, 6, 7, and 8-BPh4 have been determined by X-ray diffraction methods.