Trinuclear Pd 3 O 2 Intermediate in Aerobic Oxidation Catalysis

The activation of O 2 is a key step in selective catalytic aerobic oxidation reactions mediated by transition metals. The bridging trinuclear palladium species, [(LPd II ) 3 (μ 3 ‐O) 2 ] 2+ (L=2,9‐dimethylphenanthroline), was identified during the [LPd(OAc)] 2 (OTf) 2 ‐catalyzed aerobic oxidation of 1,2‐propanediol. Independent synthesis, structural characterization, and catalytic studies of the trinuclear compound show that it is a product of oxygen activation by reduced palladium species and is a competent intermediate in the catalytic aerobic oxidation of alcohols. The formation and catalytic activity of the trinuclear Pd 3 O 2 species illuminates a multinuclear pathway for aerobic oxidation reactions catalyzed by Pd complexes.