Although phosphorus resides immediately below nitrogen on the periodic table, the chemical behavior of the two elements is unexpectedly quite different. For example, when it comes to forming oxides, some of the most fundamental of chemical compounds, nitrogen readily forms linear NO, NO2, and N2Ox (x = 1, 3, 4, 5), whereas phosphorus forms cagelike P4O6 and P4O10. Simpler phosphorus oxides such as PO and PO2 are highly reactive and have only been studied in the gas phase or at cryogenic temperatures. Gregory H. Robinson, Yuzhong Wang, and coworkers at the University of Georgia have now found a way to stabilize diphosphorus tetroxide, P2O4, the long-sought phosphorus analog of the rocket propellant N2O4 (J. Am. Chem. Soc. 2013, DOI: 10.1021/ja411667f). Robinson’s group had previously used bulky N-heterocyclic carbene ligands to tame diphosphorus, P2, which itself is normally a transient species, unlike the ubiquitous N2. The researchers used the carbene-stabilized diphosphorus complex to split O2, forming a compound containing P2O4. This method suggests a new strategy to probe the chemistry of the highly reactive simple phosphorus oxides, Robinson says, and it could lead to useful reagents for synthesizing phosphorus-containing molecules.