Structural constraint at a P–P bond: phosphinophosphination of alkenes, alkynes, and carbonyls by a concerted mechanism

Structurally constraining p-block elements has become a powerful strategy for bond activation chemistry with main group compounds. Traditionally, this approach focuses on mononuclear centers, yet applying structural constraints to systems with element-element bonds remains underexplored. In this study, we introduce a cation featuring a structural constraint-elongated P-P bond that spontaneously adds to unactivated alkynes, alkenes, aldehydes, and ketones. Despite its positive charge, the surprisingly apolar P-P⁺ bond promotes phosphinophosphination <i>via</i> a concerted, highly regio- and diastereoselective mechanism. This unique reactivity opens pathways to novel seven-membered phosphorus heterocycles with customizable optical properties and a structurally varied array of ligands for transition metal coordination.