First use of a divalent lanthanide for visible-light-promoted photoredox catalysis

• Published in: Chemical science (Cambridge) Vol. 9; no. 5; pp. 1273 - 1278
• Main Authors: Jenks, Tyler C, Bailey, Matthew D, Hovey, Jessica L, Fernando, Shanilke, Basnayake, Gihan, Cross, Michael E, Li, Wen, Allen, Matthew J
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 2018; Royal Society of Chemistry (RSC)
• Subjects: Catalysis; Diodes; Energy consumption; Europium; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Light; Light emitting diodes; Organic light emitting diodes; Oxidation; Photoredox catalysis; Valence
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/c7sc02479g

We report the first catalytic use of a divalent lanthanide in visible-light-promoted bond-forming reactions. Our new precatalyst uses europium in the +2 oxidation state and is active in the presence of blue light from light-emitting diodes. The use of low-energy visible light reduces the occurrence of potential side reactions that might be induced by higher-energy UV light. The system described here uses zinc metal as a sacrificial reductant and is tolerant to wet, protic solvents. The catalyst can be made from relatively inexpensive and air-stable EuCl ·6H O, and the ligand can be synthesized in large quantities in two steps. With 0.5% loading of precatalyst, an average of 120 turnovers was observed in six hours for reductive coupling of benzyl chloride. We expect that the results will initiate the study of visible-light-promoted photoredox catalysis using divalent europium in a variety of reactions.