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(mu-NTer)](2) (Ter = 2,6-bis(2,4,6-trimethylphenyl)phenyl) was utilized in the activation of stable small molecules. Fast reactions with H-2, CO2, and NH3 were observed. Dihydrogen easily added to [P(mu-NTer)](2), yielding [HP(mu-NTer)](2) under ambient conditions whereas reversible release of molecular hydrogen was observed at slightly elevated temperatures (T > 60 degrees C). As [P(mu-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(mu-NTer)(2)P], and carbon monoxide. The reaction of [P(mu-NTer)](2) with ammonia led to the formation of an azadiphosphiridine after rearrangements of the central P2N2 heterocycle.