Iron Stoichiometry-Driven Pathway-Divergent C-C Couplings on Ag(110)

Precise control over intermolecular C-C couplings on surfaces would unlock the synthesis of novel organic molecules or carbon-based covalent nanoarchitectures with tunable compositions, structures, and properties. Selection of certain C-C coupling among multiple competing reaction pathways has previously been achieved by introducing specific metal adatoms. Research on how to selectively trigger pathway- or site-divergent C-C couplings from common precursor molecules remains largely unexplored, which would facilitate the controlled synthesis toward desired products. In this work, by utilizing the well-known catalyst of iron adatoms and delicately modulating iron stoichiometry, we have achieved pathway-divergent C-C couplings of 3-bromonaphthalen-2-ol molecules on Ag(110) with high selectivity, enabling selective synthesis of distinct products, especially hitherto inaccessible heterocyclic naphthofuran derivatives at higher stoichiometry. The key is that the gradually changed Fe stoichiometry induces varying degrees of hydrogen passivation of carbon radicals generated via C-Br cleavage, which significantly affects the reaction pathways of subsequent C-C couplings.