A Molybdenum(0) Isocyanide Analogue of Ru(2,2-Bipyridine)32+: A Strong Reductant for Photoredox Catalysis

We report the first homoleptic Mo-0 complex with bidentate isocyanide ligands, which exhibits metal-to-ligand charge transfer ((MLCT)-M-3) luminescence with quantum yields and lifetimes similar to Ru(bpy)(3)(2+) (bpy=2,2-bipyridine). This Mo-0 complex is a very strong photoreductant, which manifests in its capability to reduce acetophenone with essentially diffusion-limited kinetics as shown by time-resolved laser spectroscopy. The application potential of this complex for photoredox catalysis was demonstrated by the rearrangement of an acyl cyclopropane to a 2,3-dihydrofuran, which is a reaction that requires a reduction potential so negative that even the well-known and strongly reducing Ir(2-phenylpyridine)(3) photosensitizer cannot catalyze it. Our study thus provides the proof-of-concept for the use of chelating isocyanides to obtain Mo-0 complexes with long-lived (MLCT)-M-3 excited states that are applicable to unusually challenging photoredox chemistry.