Boron-Doped Pentacenes: Isolation of Crystalline 5,12- and 5,7-Diboratapentacene Dianions

The syntheses, molecular structures, reactivities, and computational assessment of dipotassium diboratapentacene isomers are described ( 1 and 2 ). These compounds represent the first examples of aromatized diboraacenes where the boron atoms are spatially separated in different rings of the acene framework. Both 1 and 2 react with carbon dioxide (CO 2 ) via diastereoselective carboxylation of the pentacene backbone that likely proceeds by a frustrated Lewis pair-like mechanism. The placement of the boron atoms and the reactivity studies provide a platform for later stage functionalization of diboraacenes beyond the central ring of the polycyclic aromatic hydrocarbon core.