Selective Cleavage of the Strong or Weak C-C Bonds in Biphenylene Enabled by Rare-Earth Metals

Selective cleavage of C-C bonds within arene rings is of great interest but remains elusive, especially for the molecules possessing the active and inert C-C bonds. Here, we report that the active and inert C-C bonds of biphenylene could be controllably cleaved by the reaction of biphenylene, potassium graphite, and rare-earth complexes with different metal centers. For scandium, the bond activation occurs at the Caryl-Caryl single bond, yielding 9-scandafluorene. For Lu, the reaction goes through ring contraction of the aromatic ring in biphenylene to provide benzopentalene dianionic lutetium. The origin of the selectivity and the reaction mechanism were illustrated by the isolation of intermediates and DFT calculations.

Automated summary

In this study, we demonstrate the controllable cleavage of active and inert C-C bonds within biphenylene through the reaction with potassium graphite and rare-earth complexes with different metal centers. The Caryl-Caryl single bond is activated, producing 9-scandafluorene, when scandium is used as the reaction center. On the other hand, the aromatic ring in biphenylene undergoes ring contraction to form benzopentalene dianionic lutetium when Lu is the reaction center. The selectivity and reaction mechanism are elucidated by isolating intermediates and conducting DFT calculations.