Iridium Complexes Containing a PNP Pincer Ligand: Syntheses, Structural Chemistry, and Bond Activations



The coordination chemistry of the monoanionic PNP pincer ligand 3,6-di-tert-butyl-1,8-bis[(diphenylphosphanyl)methyl]carbazole (Cbzdiphos) was investigated for different iridium(I) and iridium(III) complexes. Reaction of the protio ligand with [Ir(acac)(cod)] (acac = acetylacetonate; cod = 1,5-cyclooctadienyl) gave [(Cbzdiphos)Ir(cod)] (1). Upon hydrogenation the dihydrido complex [(Cbzdiphos)IrH2] (2) was obtained, and its reactivity in different organometallic transformations was examined. Treating 2 with ammonia afforded [(Cbzdiphos)IrH2(NH3)] (3), whereas treatment with diphenylacetylene (dpa) yielded the IrI compound [(Cbzdiphos)Ir(dpa)] (4) and trans-stilbene. Furthermore, the conversion with norbornene led to a reactive species, which activated C–H and C–Cl bonds. The reaction with THF gave a Fischer carbene [(Cbzdiphos)Ir{=C(OC3H6)}] (8) after double C–H bond activation, whereas treatment with benzene or chlorobenzene afforded the oxidative addition products [(Cbzdiphos)Ir(Ph)H] (5) and [(Cbzdiphos)Ir(Ph)Cl] (7).