Straining to React: Delocalization Drives the Stability and Omniphilicity of [1.1.1]propellane

The highly strained caged hydrocarbon [1.1.1]propellane has long fascinated chemists with its seemingly paradoxical stability, yet promiscuous reactivity. In this work, we present a unified model of reactivity that accounts for its omniphilic character. Through Complete Active Space (CAS) calculations, state-of-the-art coupled-cluster methods [DLPNO-CCSD(T)] and DFT approaches, we challenge the hypothesis that reactivity of [1.1.1]propellane is driven by strain relief. Instead, a highly delocalized ground-state electronic structure is proposed, where HOMO-LUMO mixing gives a moldable electron density that results in omniphilicity.