Harnessing redox-inactive rare-earth metals for photocatalytic reductive coupling of benzyl bromides

Compared with rare and expensive late-transition metals, rare-earth photocatalysts are much less investigated in synthetic chemistry, particularly concerning redox-inactive rare-earth metals. Herein, we describe a general strategy to realize the redox-inactive rare-earth photocatalysis by grafting a light-absorbing scaffold onto common ligands in rare-earth organometallics. Three guanidinate rare-earth complexes with photocatalytic functions were synthesized and found to exhibit higher catalytic efficiency than phenothiazine in the reductive homocoupling of benzyl bromides. These preliminary results illustrated that our "grafting" strategy could serve as a facile methodology for the construction of redox-inactive rare-earth photocatalysis systems.