Redox-induced dimerisations of a phosphacyclic biradicaloid

Despite the first examples being isolated more than two decades ago, little is known about the redox chemistry of stable phosphacyclic biradicaloids. Here, we demonstrate that a biradicaloid featuring a diphosphaindenyl backbone is able to undergo both oxidation and reduction reactions. One-electron oxidation results in the formation of a dicationic cage compound structurally related to an isomer of hypostrophene (C₁₀H₁₀). Reduction of PPIPh with [Co₂(CO)₈] results in the formation of the bimetallic complex 2, which contains a bis(benzodiphosphole) ligand.