A Molybdenum(0) Isocyanide Analogue of [Ru(2,2'-Bipyridine)3]2+: Strong Reductant for Photoredox Catalysis

We report the first homoleptic Mo0 complex with bidentate isocyanide ligands, which exhibits metal-to-ligand charge transfer (3MLCT) luminescence with quantum yields and lifetimes similar to Ru(bpy)32+ (bpy=2,2′-bipyridine). This Mo0 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 Mo0 complexes with long-lived 3MLCT excited states that are applicable to unusually challenging photoredox chemistry.