Ring expansion of osmacyclopentadiene affords diverse six-membered osmaaromatics.

Metallaromatics such as metallabenzene and its heteroatom-containing analogues have aroused interests both in experimental and theoretical studies. While various six-membered metallaaromatics have been explored, a general synthetic methodology is still undeveloped. Herein, we report the skeletal editing of five-membered metallacyclopentadiene involving the insertion of the sixth atoms (S, Se, N, C) into the Os-C bond, as a general approach for osmafluoranthene derivatives containing osmathiabenzene, osmaselenabenzene, osmapyridine, and osmabenzene units. These complexes show broad UV-Vis absorptions, and their aromaticity has been authenticated spectroscopically, structurally and computationally.