Synthesis and Catalytic Applications of Stable Palladium Dioxygen Complexes

The synthesis and characterization of air-stable palladium dioxygen complexes Pd(O2)L2 of basic phosphines L = P(1-Ad)2nBu, PtBu2nBu is described. Contrary to general belief, these dioxygen complexes are stable catalyst precursors for palladium-catalyzed coupling reactions. Specifically, palladium-catalyzed formylations and alkoxy carbonylations of aryl bromides proceed in high yield in air using commercial non-degassed solvents. It is shown that Pd(O2)L2 complexes are reduced back to the catalytically active palladium(0) species in the reductive atmosphere of CO or H2 at the onset of the carbonylation reaction.