Atom Swapping Reaction on Diborylcarbenoid: Synthesis and Electronic Structure of Inorganic Chalcogenophene Analogues

Inorganic analogues of aromatic compounds, wherein C═C bonds are replaced with B─N bonds, are isoelectronic with the original aromatic compounds, however, they can show different properties. While borazine, an inorganic analogue of benzene, has been well-studied, inorganic analogues of chalcogenophene have been less explored. Here, we synthesized crystalline isolable inorganic furan 2_O and thiophene 2_S by atom swapping reaction at the carbenoid carbon of K/Cl-diborylcarbenoid, an equivalent to diborylcarbene. Density functional theory calculation exhibited that, in contrast to the quite weak aromatic character of borazine, inorganic chalcogenophenes 2_O and 2_S have a moderate aromaticity. Theoretical investigation of the reaction mechanism suggested that the atom swapping reaction occurred via oxidation of diborylcarbenoid 1 to diboralactone intermediate 3_Ch and the following intramolecular rearrangement reaction.