Isolation of Neutral, Mono?, and Dicationic B ₂ P ₂ Rings by Diphosphorus Addition to a Boron?Boron Triple Bond

The NHC-stabilised diboryne (B2(SIDep)2; SIDep=1,3-bis(2,6-diethylphenyl)imidazolin-2-ylidene) undergoes a high-yielding P?P bond activation with tetraethyldiphosphine at room temperature to form B2P2 heterocycle via diphosphoryldiborene by 1,2-diphosphination. can be oxidised radical cation and dication, respectively, depending on the oxidant used its counterion. Starting from planar, neutral 1,3-bis(alkylidene)-1,3-diborata-2,4-diphosphoniocyclobutane, each oxidation step leads decreased B?B distances loss of planarity cationisation. X-ray analyses in conjunction DFT CASSCF/NEVPT2 calculations reveal closed-shell singlet, butterfly-shaped structures for dicationic rings, their diradicaloid, planar-ring isomers lying close energy.