On-surface chemistry is an interesting research area. Often, unprecedented structures can be synthesized on surfaces—for example, functional nanomaterials. Desilylative reactions involving C–Si bond cleavage are well-known in solution chemistry. In contrast to this, desilylation in on-surface chemistry is limited. There are known examples of C(sp)–Si cleavage, while C(sp²)–Si cleavage on a metal surface had not been achieved so far.

Zhixiang Sun, You Han, Hong-Ying Gao, Tianjin University, China, Dongbing Zhao, Nankai University, Tianjin, China, and colleagues have developed reactions that involve C(sp²)–Si bond cleavages on metal surfaces (pictured). The team tested four precursors for such reactions, i.e., 1-trimethylsilyl-4-bromo-naphthalene (1,4-TBN, pictured above), 2-trimethylsilyl-6-bromo-naphthalene (2,6-TBN), 1,4-bis(trimethylsilyl)naphthalene (1,4-BTN), and 1,4-dibromonaphthalene (1,4-DBN). The reactions were performed on Au(111), Ag(111), or Cu(111) surfaces.

Using high-resolution scanning tunneling microscopy (STM), the team found that 1,4-TBN molecules form an ordered, self-assembled, chain-like structure when deposited on an Au(111) surface. Thermal annealing then led to the cleavage of C–Br and C(sp²)–Si bonds and C–C coupling reactions.

Annealing at 250 °C gave poly-naphthalene chains. Further annealing at 300 °C then led to 5-armchair graphene nanoribbons (5-AGNRs), formed by partial cyclodehydrogenation. According to the researchers, this is the first successfully realized C(sp²)–Si desilylation on a surface.

• Desilylative Coupling Involving C(sp²)–Si Bond Cleavage on Metal Surfaces,
  Kang Ma, Tiantong Zhang, Ying Qin, Zhixin Hu, Zhixiang Sun, You Han, Dongbing Zhao, Hong-Ying Gao,
  J. Am. Chem. Soc. 2022.
  https://doi.org/10.1021/jacs.2c02762