A visible-light activated secondary phosphine oxide ligand enabling Pd-catalyzed radical cross-couplings

Ligand design is key for improving the performance in light-enabled catalytic processes. Here, the authors report the synthesis of a visible-light-activated secondary phosphine oxide ligand and apply it to Pd-catalyzed radical cross-coupling reactions. Although transition metal-catalyzed reactions have evolved with ligand development, ligand design for palladium-catalyzed photoreactions remains less explored. Here, we report a secondary phosphine oxide ligand bearing a visible-light sensitization moiety and apply it to Pd-catalyzed radical cross-coupling reactions. The tautomeric phosphinous acid coordinates to palladium in situ, allowing for pseudo-intramolecular single-electron transfer between the ligand and palladium. Molecular design of the metal complexes aided by time-dependent density functional theory calculations enables the involvement of allyl radicals from pi-allyl palladium(II) complexes, and alkyl and aryl radicals from the corresponding halides and palladium(0) complex. This complex enables radical cross-couplings by ligand-to-Pd(II) and Pd(0)-to-ligand single-electron transfer under visible-light irradiation.

Automated summary

Ligand design plays a crucial role in enhancing the performance of light-enabled catalytic processes. In this study, the authors synthesized a visible-light-activated secondary phosphine oxide ligand and applied it to Pd-catalyzed radical cross-coupling reactions. Through molecular design aided by computational calculations, the ligand enables ligand-to-Pd(II) and Pd(0)-to-ligand single-electron transfer under visible-light irradiation, facilitating radical cross-coupling reactions.