Photoexcitation of Distinct Divalent Palladium Complexes in Cross-Coupling Amination Under Air

The development of metal complexes that function as both photocatalyst and cross-coupling catalyst remains a challenging research topic. So far, progress has been shown in palladium(0) excited-state transition metal catalysis for the construction of carbon-carbon bonds where the oxidative addition of alkyl/aryl halides to zero-valent palladium (Pd0) is achievable at room temperature. In contrast, the analogous process with divalent palladium (PdII) is uphill and endothermic. For the first time, we report that divalent palladium can act as a light-absorbing species that undergoes double excitation to realize carbon-nitrogen (C-N) cross-couplings under air. Differently substituted aryl halides can be applied in the mild, and selective cross-coupling amination using palladium acetate as both photocatalyst and cross-coupling catalyst at room temperature. Density functional theory studies supported by mechanistic investigations provide insight into the reaction mechanism. A palladium photocatalytic method is reported for the successful synthesis of primary anilines by the cross-coupling of aryl halides and sodium azide under open-air conditions at room temperature. For the first time, diverse divalent palladium complexes are shown to undergo photoexcitation to give carbon-nitrogen (C-N) cross-coupled product under air without using sophisticated ligands.+image