Halogen Photoreductive Elimination from Metal−Metal Bonded Iridium(II)−Gold(II) Heterobimetallic Complexes

Halogen oxidation of [IrIAuI(dcpm)2(CO)X](PF6) (dcpm = bis(dicyclohexylphosphino)methane, X = Cl, Br) and [IrIAuI(dppm)2(CNtBu)2](PF6)2 (dppm = bis(diphenylphosphino)methane) furnishes the heretofore unknown class of d7d9 compounds comprising an IrIIAuII heterobimetallic core. A direct metal−metal bond is evident from a 0.2 Å contraction in the intermetallic distance, as determined by X-ray crystallography. The photophysical consequence of iridium−gold bond formation, as elucidated by experimental and computational investigations, is an electronic structure dominated by a σ → σ* transition that possesses significant ligand-to-metal charge transfer (LMCT) character. Accordingly, these compounds are non-emissive but photoreactive. Excitation of IrIIAuII complexes in the presence of a halogen trap prompts a net photoreductive elimination of halogen and the production of the two-electron reduced IrIAuI species with about 10% quantum efficiency. The IrIIAuII complexes add to a growing library of d7d9 heterobimetallic species from which halogen elimination may be driven by a photon.