Electron-Rich CpIr(biphenyl-2,2'-diyl) Complexes with π-Accepting Carbon Donor Ligands

Cp*Ir^III and CpIr^III complexes have attracted interest as catalysts for oxidative transformations, and highly oxidizing iridium species are postulated as key intermediates in both catalytic water and C-H bond oxidation. Strongly electron-donating ligand sets have been shown to stabilize Ir^IV complexes. We describe the synthesis and reactivity of complexes containing the CpIr(biphenyl-2,2'-diyl) moiety stabilized by a series of strong donor carbon-based ligands. The oxidation chemistry of these complexes has been characterized electrochemically, and a singly oxidized Ir^IV species has been observed by X-band EPR for the complex CpIr(biph)(p-CNCH₂SO₂C₆H₄CH₃).