Understanding the Organometallic Step: SO₂ Insertion into Bi(III)-C(Ph) Bond

Heavier main-group element-catalyzed reactions provide an increasingly attractive tool to perform transformations mimicking the behaviors of transition metal catalysts. Recently, Magre and Cornella reported a Bi-catalyzed synthesis of aryl sulfonyl fluorides, which involves a fundamental organometallic step of SO2 insertion into the Bi-Ph bond. Our theoretical studies reveal that i) the ability of hypervalent coordination of the Bi(III) center allows facile coordination sphere expansion for the SO2 coordination via one oxygen atom; and ii) the high polarity of the Bi-Ph bond makes the Ph migration from the Bi(III) center feasible. These features enable the heavier main group element to resemble the transition metal having flexibility for ligand association and dissociation. Furthermore, iii) the available pi electron pair of the migrating Ph group stabilizes the SO2 insertion transition state by maintaining interaction with the Bi(III) center during migration. The insight helps us better understand the heavier main-group catalysis.