A group of UGA chemists led by Yuzhong Wang and Gregory H. Robinson have prepared the first stable molecule containing diphosphorus tetroxide, P2O4, via a novel approach involving the reaction of molecular oxygen with the base-stabilized diphosphorus. The base involved belongs to an important class of donor bases known as N-heterocyclic carbenes. Diphosphorus tetroxide is the long-sought phosphorus analog of the rocket propellant N2O4. Although phosphorus lies immediately beneath nitrogen on the Periodic Table, the chemistry of these first two pnictogens could not be more different. For example, while nitrogen gas (N2) is ubiquitous (making up nearly 80% of the earth’s atmosphere), P2 is transient and generally only observed at high temperatures. Moreover, the chemistry of nitrogen oxides is extensive and well developed while the chemistry of simple phosphorus oxides is considerably less well understood due to their high reactivity. Consequently, simple phosphorus oxides have generally only been studied computationally or in argon matrices. Indeed, UGA computational chemists Yaoming Xie, Paul von R. Schleyer and H. Fritz Schaefer collaborated with Wang and Robinson on this study. Unlike dinitrogen tetroxide, which has a symmetrical O2N-NO2 ground state structure, computations suggested that the diphosphorus tetroxide ground state conformation was the asymmetric O2P-O-PO isomer. However, these chemists were able to “trap” this highly reactive molecule in the less stable symmetrical O2P-PO2 isomer. Significantly, this carbene-stabilized diphosphorus tetroxide represents the first example of a phosphorus oxide exhibiting Lewis Acid behavior. Robinson believes that this result suggests a new synthetic strategy to probe the chemistry of the highly reactive simply phosphorus oxides. This work, funded by the National Science Foundation, was recently published in the Journal of the American Chemical Society (2013, 135, 19139-19142; DOI: 10.1021/ja411667f), and cited in both Chemical & Engineering News and Chemistry World.
