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.