Activation of Alkynes by a Redox-Active Carboranyl Diphosphine and Formation of Boron-Containing Phosphacycles

In this work, we report the reactivity of the carboranyl diphosphine, 1-P^tBu₂–2-PⁱPr₂-C₂B₁₀H₁₀, with terminal alkynes, resulting in the formation of boron-containing phosphacycles. The reported system combines the nucleophilic activation of electron-deficient terminal alkynes via electron-rich phosphine groups with the redox behavior of carborane clusters to promote a sequence of metal-free intramolecular B–H bond activation and cyclization, creating an alkenylphosphonium cycle fused with a reduced open nido-carborane cluster.