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The first phosphaphosphenium cation isolated

Chemists prepare HP2+, the elusive phosphorus analog of the diazonium cation

by Stephen K. Ritter
April 25, 2016 | A version of this story appeared in Volume 94, Issue 17

Researchers who spend their time seeking out strange new molecules made from main-group elements have enjoyed great success in recent years thanks to the discovery of N-heterocyclic carbenes (NHCs). These Lewis bases with a sturdy lone pair of electrons can bind and stabilize metals and molecule fragments in ways not possible before. In the latest example, Yuzhong Wang, Gregory H. Robinson, and coworkers of the University of Georgia have used the NHC-stabilization strategy to prepare the parent phosphaphosphenium cation, HP2+, for the first time. The complexity of the cation’s name hints that chemists have had a complex time isolating the deceptively simple species, previously only detecting it in gas-phase experiments. To make HP2+, Robinson and coworkers used pyridine hydrochloride (HCl•NC5H5) to protonate NHC-stabilized diphosphorus, P2, another compound they previously tamed. Unlike its nitrogen analog, N2, diphosphorus is unstable. The Georgia team further obtained the X-ray crystal structure of NHC-stabilized HP2+ and conducted spectroscopic and computational bonding analyses (Chem. Commun. 2016, DOI: 10.1039/c6cc0175b). The findings could lead to better understanding of how to use diphosphorus in organic synthesis and materials science, for example, similar to how aryl diazonium cations RN2+ are used in palladium-catalyzed cross-coupling reactions.


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