Flash Of Phosphorus Chemistry Innovation

With ultraviolet light, Massachusetts Institute of Technology researchers have developed another potential industrial route to organophosphorus compounds that avoids toxic, tough-to-handle chlorine. Phosphorus atoms abound in pesticides, fertilizers, and more. But to make these compounds from naturally available white phosphorus, P₄, researchers have typically resorted to treating P₄ with chlorine gas to make PCl₃, and then reacting PCl₃ with organic molecules. Daniel Tofan and Christopher C. Cummins have now used a photochemical approach instead to generate cyclic organophosphorus compounds called diphosphanes directly from P₄ (Angew. Chem. Int. Ed., DOI: 10.1002/anie.201004385). They suggest the strategy could complement other chlorine-free methods, including some already developed by Cummins’ group (C&EN, Aug. 9, page 8). Inspired by research published more than 70 years ago, Tofan and Cummins exposed a mixture of P₄ and an organic diene to UV light for half a day, obtaining diphosphane products. The outcome indicates that P₂, a molecule unstable under typical organic synthesis conditions, is likely made during the course of the reaction, Cummins says. In the future, he hopes to catch P₂ in the act.