Intermolecular On-Surface Sigma-Bond Metathesis

Silylation and desilylation are important functional group manipulations in solution-phase organic chemistry that are heavily used to protect/deprotect different functionalities. Herein, we disclose the first examples of the sigma-bond metathesis of silylated alkynes with aromatic carboxylic acids on the Ag(111) and Au(111) surfaces to give the corresponding terminal alkynes and silyl esters, which is supported by density functional theory calculations and further confirmed by X-ray photoelectron spectroscopy analysis. Such a protecting group strategy applied to on-surface chemistry allows self-assembly structures to be generated from molecules that are inherently unstable in solution and in the solid state. This is shown by the successful formation of self-assembled hexaethynylbenzene at Ag(111). Furthermore, it is also shown that on the Au(111) surface this sigma-bond metathesis can be combined with Glaser coupling to fabricate covalent polymers via a cascade process.