Metallapentalenofurans and Lactone-Fused Metallapentalynes

Metalla-aromatics are attractive species because they exhibit the properties of both organometallics and aromatics. Reported metal-bridged polycyclic aromatic complexes, as well as Mobius aromatic species, are still rare. Herein, we present the construction of two new metal-bridged polycyclic aromatic frameworks, α-metallapentalenofurans and lactone-fused metallapentalynes, by the reactions of osmapentalyne with terminal aryl alkynes in the presence of H2O or HBF4/H2O, respectively. DFT calculations show that the α-metallapentalenofurans possess rare planar Craig-type Mobius aromaticity derived from the 11-center-12-electron dπ–pπ π-conjugation. This study offers a new route for the construction of polycyclic metalla-aromatics as well as planar Mobius aromatic species.