Reactions of Metal-Carbon Bonds within Six-Membered Metallaaromatic Rings

Metallaaromatics represent a distinct and attractive class of heterocycles, which have greatly expanded the library of known aromatics. They have garnered extensive research interest on account of their unique properties, organometallic reactivity, and aromaticity. The metal-carbon bonds have been regarded as the most active reaction sites of metallaaromatics and a variety of related reactions have been demonstrated in the literature. This Minireview summarized recent findings on the reactivity of the metal-carbon bonds, mainly relevant to the representative metallaaromatics with six-membered ring scaffolds. A series of reactions occurred on the metal-carbon bonds, including the nucleophilic addition reactions, nucleophilic aromatic substitution reactions, electrophilic addition reactions, reactions with unsaturated compounds, and migratory insertion reactions, have been classified. These reactions demonstrate that the metal-carbon bonds of metallaaromatics can undergo typical reactions for both aromatic species and metal carbene/carbyne complexes. Meanwhile, the reactivity trends of the metal-carbon bonds are strongly affected by the metal centers and the effect of the corresponding substituents of metallacycles.