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

Abstract

We report the first homoleptic Mo(0) complex with bidentate isocyanide ligands, which exhibits metal-to-ligand charge transfer ((3) MLCT) 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 (3) MLCT excited states that are applicable to unusually challenging photoredox chemistry.

Deuterated Molecular Ruby with Record Luminescence Quantum Yield

“…[1,2] Except for copper(I) complexes, [2] strongly luminescent molecular complexes of earth-abundant-metal ions were essentially unknown until very recently.N ear-IR (NIR) emission with mononuclear copper(I) complexes is still very rare. [4][5][6][7][8] Milsmann and co-workers reported aluminescent zirconium-(IV) complex bearing 2,6-bis(pyrrolyl)pyridine ligands. [3] Ah andful of examples of luminescent complexes based on earth-abundant-metal ions with d n electron configuration (n < 10) only became available in the last three years (Scheme 1).…”

“…They include ligand-to-metal charge transfer (LMCT), metal-to-ligand (MLCT), and spin-flip emitters. [6,7] Thec hromium(III) complex [Cr(ddpd) 2 ] 3+ (1 3+ ) [8] with ad 3 electron configuration is based on the tridentate strongfield ligand N,N'-dimethyl-N,N'-dipyridine-2-yl-pyridine-2,6diamine (ddpd) introduced into coordination chemistry by the Heinze group (Scheme 1). [4] A unique low-spin hexacarbene iron(III) complex with LMCT emission has been reported by Wärnmark.…”

“…[4] A unique low-spin hexacarbene iron(III) complex with LMCT emission has been reported by Wärnmark. [4][5][6][7][8] [*] C. Wang displays asharp,unprecedentedly intense spin-flip emission in the NIR with aphotoluminescence quantum yield of F = 0.11 and al uminescence lifetime of t = 898 msi nH 2 Oa tr oom temperature. [6,7] Thec hromium(III) complex [Cr(ddpd) 2 ] 3+ (1 3+ ) [8] with ad 3 electron configuration is based on the tridentate strongfield ligand N,N'-dimethyl-N,N'-dipyridine-2-yl-pyridine-2,6diamine (ddpd) introduced into coordination chemistry by the Heinze group (Scheme 1).…”

“…[5] Wengersd 6 metal(0) isocyanide chelate complexes display MLCT luminescence in solution (Scheme 1). [8] Emerging novel applications of these extraordinary emitters such as triplet-triplet annihilation upconversion, [6a] demanding photoredox reactions, [6] optical temperature sensing with as ingle dye [10] and selective energy transfer/singlet oxygen formation [11] have already been realized in this short time and ap lethora of others are expected in the future. [9] The" molecular ruby" 1 3+ Scheme 1.…”

Blue‐Emissive Cobalt(III) Complexes and Their Use in the Photocatalytic Trifluoromethylation of Polycyclic Aromatic Hydrocarbons

“…[4] Some fruitful approaches to destabilize the energy of the 3 MC states consist of a) introduction of strong donor ligands and b) the use of tridentate ligands that form 6-membered chelate rings to reduce the steric strain and achieve am ore octahedral geometry compared to those bearing five-membered chelate rings. Recently,W enger and Gray et al observed 3 MLCT emission of earth abundant low-valent Cr 0 , [13] Mo 0 , [14] and W 0 [15] complexes with arylisocyanide ligands. Recently,W enger and Gray et al observed 3 MLCT emission of earth abundant low-valent Cr 0 , [13] Mo 0 , [14] and W 0 [15] complexes with arylisocyanide ligands.…”