Electrophilic Substitution Reactions of Metallabenzynes

The electrophilic substitution reactions of metallabenzynes Os(CC(R)C(CH₃)C(R)CH)Cl₂(PPh₃)₂ (R = SiMe₃, H) were studied. These metallabenzynes react with electrophilic reagents, including Br₂, NO₂BF₄, NOBF₄, HCl/H₂O₂, and AlCl₃/H₂O₂ to afford the corresponding bromination, nitration, nitrosation, and chlorination products. The reactions usually occur at the C2 and C4 positions of the metallacycle. These observations support the notion that metallabenzynes exhibit aromatic properties.