Metal-Free Activation of Hydrogen, Carbon Dioxide, and Ammonia by the Open-Shell Singlet Biradicaloid [P(μ-NTer)]2

The Group 15 open‐shell singlet biradicaloid [P(μ‐NTer)]2 (Ter=2,6‐bis(2,4,6‐trimethylphenyl)phenyl) was utilized in the activation of stable small molecules. Fast reactions with H2, CO2, and NH3 were observed. Dihydrogen easily added to [P(μ‐NTer)]2 , yielding [HP(μ‐NTer)]2 under ambient conditions whereas reversible release of molecular hydrogen was observed at slightly elevated temperatures (T>60 °C). As [P(μ‐NTer)]2 is a species with phosphorus in the unusual formal oxidation state +II, it is capable of reducing carbon dioxide to afford a zwitterionic compound, [OP(μ‐NTer)2P], and carbon monoxide. The reaction of [P(μ‐NTer)]2 with ammonia led to the formation of an azadiphosphiridine after rearrangements of the central P2N2 heterocycle. Don't wait for activation: The singlet biradicaloid [P(μ‐NTer)]2 readily reacts with H2, CO2, or NH3 at ambient temperature. The addition of H2 is reversible whereas CO2 is reduced to CO with formation of “biradicaloid monoxide”. Activation of ammonia causes the P2N2 scaffold to rearrange to give an azadiphosphiridine.