Lewis Acid/Base Au-Mn Pairs in Metal Nanoclusters for Enhanced Photocatalytic C(sp2)-H Arylation.

Integrating polar bimetallic active sites on the metal nanocatalysts for advanced cross-coupling reactions holds great promise, yet is challenging. Here, we report the successful synthesis of Lewis acid/base bimetallic nanocluster Au20Mn2 and demonstrate its catalytic potential in visible-light-driven direct C(sp2)-H arylation of aryl halides. The cluster comprises two Au11 incomplete icosahedra fused into an Au20 kernel, which features four uncoordinated gold atoms in a rhombic pattern and is protected by two bridged Mn(CO)5 moieties. Experimental and computational studies disclose that the Mn sites function as electron donors, facilitating polarized Au(δ+)-Mn(δ-) bonds with pronounced [Mn(CO)5]-→Au20 σ donation interactions. The Lewis acid/base pair bestows Au20Mn2 with exceptional photocatalytic performance in C(sp2)-H arylation of various substituted (hetero)aryl bromides and chlorides with electron-rich-to-deficient arenes under mild conditions. This protocol boasts high functional group tolerance, supports gram-scale synthesis, and is applicable to both the late-stage functionalization of complex molecules and the targeted synthesis of bioactive products. Mechanism analyses uncover that the collaboration between the gold-involved single electron transfer activation of aryl halides and Mn π-base activation of arenes accounts for the remarkable efficiency of this system.