Halogen Photoelimination from Sb Dihalide Corroles.

Main-group p-block metals are ideally suited for mediating two-electron reactions because they cycle between M and M redox states, as the one-electron state is thermodynamically unstable. Here, we report the synthesis and structure of an Sb corrole and its SbX (X = Cl, Br) congeners. Sb sits above the corrole ring, whereas Sb resides in the corrole centroid. Electrochemistry suggests interconversion between the Sb and SbX species. TD-DFT calculations indicate a HOMO → LUMO+2 parentage for excited states in the Soret spectral region that have significant antibonding character with respect to the Sb-X fragment. The photochemistry of 2 and 3 in THF is consistent with the computational results, as steady-state photolysis at wavelengths coincident with the Soret absorption of SbX corrole lead to its clean conversion to the Sb corrole. This ability to photoactivate the Sb-X bond reflects the proclivity of the pnictogens to rely on the Pn couple to drive the two-electron photochemistry of M-X bond activation, an essential transformation needed to develop HX-splitting cycles.