Serendipitous Discovery of a Simple Compound with an Unsupported Ir−Ir Bond

The long-known compound Ir(acac)(CO)₂ (acac = 2,4-pentanedionato) undergoes a formal oxidation reaction when treated with AgOTf (Tf = CF₃SO₂) to give the dinuclear complex [Ir(acac)(OTf)(CO)₂]₂, containing an unsupported Ir−Ir bond. The compound has been characterized by a single-crystal X-ray diffraction study, and DFT and NBO calculations have been employed to probe the nature of the Ir−Ir bond. Reduction of the complex regenerates Ir(acac)(CO)₂.