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Abstract Several renewable energy schemes aim to use the chemical bonds in abundant molecules like water and ammonia as energy reservoirs. Because the O-H and N-H bonds are quite strong (>100 kcal/mol), it is necessary to identify substances that dramatically weaken these bonds to facilitate proton-coupled electron transfer processes required for energy conversion. Usually this is accomplished through coordination-induced bond weakening by redox-active metals. However, coordination-induced bond weakening is difficult with earth’s most abundant metal, aluminum, because of its redox inertness under mild conditions. Here, we report a system that uses aluminum with a redox non-innocent ligand to achieve significant levels of coordination-induced bond weakening of O-H and N-H bonds. The multisite proton-coupled electron transfer manifold described here points to redox non-innocent ligands as a design element to open coordination-induced bond weakening chemistry to more elements in the periodic table. 

Abstract The amination of aryl halides with palladium catalysts (Buchwald‐Hartwig amination) is a widely used transformation in synthetic and drug discovery chemistry. In this report, we demonstrate that a monometallic 2‐phosphinoimidazole Pd catalyst exhibits comparable or enhanced reactivity when compared to all ligands screened for room temperature amination of aryl chlorides with secondary amines. The di‐tert‐butylphosphine derivative showed extremely high reactivity while the di‐isopropyl variant led to almost complete loss of catalytic activity. Computational and experimental mechanistic and kinetic studies indicate that a monometallic Pd structure rather than a bimetallic Pd structure is key to fast catalysis. The di‐tert‐butylphosphine ligand has fast catalysis because it thermodynamically disfavors the formation of a much less active bimetallic Pd complex. A wide substrate scope is demonstrated for the arylation of secondary amines with aryl chlorides using our new catalyst system.