Silyl Radical Formation from Silanethiols via Sulfur Atom Transfer with Phosphinites

Silanethiols facilitate H atom-transfer processes in a variety of radical-mediated reactions. This work outlines how silanethiols form silyl radical intermediates via S atom transfer to phosphinites, as detected by isotopically labeled H atom transfer, halogen atom transfer, and alkene hydrosilylation. This contrasts with other thermodynamically downhill S atom-transfer processes via selective phosphoranyl radical fragmentation, as the process for silanethiols is essentially thermoneutral and likely favorable due to radical polarity matching.