Trinuclear Pd₃O₂ intermediate in aerobic oxidation catalysis

The activation of O2 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 Pd3O2 species illuminates a multinuclear pathway for aerobic oxidation reactions catalyzed by Pd complexes.