Catalytic Non-Oxidative C-C Coupling of Benzene to Biphenyl Over Sub-Nanostructured Europium Hydride

Catalytic coupling of benzene to biphenyl through direct C─H bond activation and C─C bond construction represents an ideal, atom-economical strategy, offering a streamlined alternative to classical multi-step functionalization approaches, and thus has been a long-sought after goal. Herein, we report that such a pathway can be realized over a sub-nanostructured europium hydride (Eu-H) catalyst under mild condition. The Eu-H catalyst achieved a biphenyl production of 53.7 mmol g_Eu ^-1 with a turnover number (TON) of 16.3 over 144 h at 150 °C. Mechanistic studies suggest that hydride species (H^-) in Eu-H preferentially deprotonate benzene to form a [C₆H₅-Eu] intermediate, which subsequently undergoes nucleophilic attack on another benzene molecule, resulting in biphenyl formation and regeneration of the Eu-H species to complete the catalytic cycle. This work not only provides a strategy for benzene coupling to biphenyl but also demonstrates the promising role of hydrides in transforming arenes into value-added molecules.