In Situ Monitoring of Transmetallation in Electric Potential-Promoted Oxidative Coupling in a Single-Molecule Junction

Abstract

To monitor and investigate chemical reactions in real time and in situ is a long-standing, challenging goal in chemistry. Herein, an electric potential-promoted oxidative coupling reaction of organoboron compounds without the addition of base is reported, and the transmetallation process involved is monitored in real time and in situ with the scanning tunneling microscopy break single-molecule junctions (STMBJ) technique. We found that the electric potential applied determined the transmetallation. At low-bias voltage, the first-step transmetallation process occurred and afforded Au-C-bonded aryl gold intermediates. The electronic properties of organoboron compounds have a strong influence on the transmetallation process, and electron-rich compounds facilitate this transformation. At high-bias voltage, the second-step transmetallation process took place, and the corresponding intermediate (highly reactive diaryl metal complex) was detected with the assistance of Pd(OAc)2. Our work demonstrates the applications of STMBJ on in situ monitoring and catalyzing of chemical reactions and provides a new methodology to fabricate single-molecule devices.