Precise Monoselective Aromatic C–H Bond Activation by Chemisorption of Meta-Aryne on a Metal Surface

• Published in: Journal of the American Chemical Society Vol. 140; no. 24; pp. 7526 - 7532
• Main Authors: Fan, Qitang, Werner, Simon, Tschakert, Jalmar, Ebeling, Daniel, Schirmeisen, André, Hilt, Gerhard, Hieringer, Wolfgang, Gottfried, J. Michael
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 20-06-2018
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.8b01658

Aromatic C–H bond activation has attracted much attention due to its versatile applications in the synthesis of aryl-containing chemicals. The major challenge lies in the minimization of the activation barrier and maximization of the regioselectivity. Here, we report the highly selective activation of the central aromatic C–H bond in meta-aryne species anchored to a copper surface, which catalyzes the C–H bond dissociation. Two prototype molecules, i.e., 4′,6′-dibromo-meta-terphenyl and 3′,5′-dibromo-ortho-terphenyl, have been employed to perform C–C coupling reactions on Cu(111). The chemical structures of the resulting products have been clarified by a combination of scanning tunneling microscopy and noncontact atomic force microscopy. Both methods demonstrate a remarkable weakening of the targeted C–H bond. Density functional theory calculations reveal that this efficient C–H activation stems from the extraordinary chemisorption of the meta-aryne on the Cu(111) surface, resulting in the close proximity of the targeted C–H group to the Cu(111) surface and the absence of planarity of the phenyl ring. These effects lead to a lowering of the C–H dissociation barrier from 1.80 to 1.12 eV, in agreement with the experimental data.