Hyperhalogen Tamed As A Supersalt

A few years ago, Puru Jena of Virginia Commonwealth University and colleagues discovered a class of compounds with unprecedented electronegativities, which they called hyperhalogens. These compounds are made of a metal atom surrounded by superhalogens—which themselves are highly electronegative molecules made of a central atom surrounded by an electronegative element or group. Hyperhalogens hold promise as superoxidizers that could be used as a rocket fuel or as hydrogen storage materials if they can be tamed into a stable form. Jena has now teamed up with Ragaiy Zidan of Savannah River National Laboratory and Rana Mohtadi of Toyota Research Institute of North America to synthesize and characterize a stable hyperhalogen salt, K[Al(BH₄)₄], whose anion, Al(BH4)4^-, has an extremely high electron affinity (J. Phys. Chem. C 2013, DOI: 10.1021/jp407230a). They prepared the compound by coupling Al(BH₄)₃ with KBH₄. Unlike the few hypersalts synthesized so far, this new salt is stable at temperatures of up to 154 °C. Besides providing a new functional material, the work validates the use of computational studies for rational design of new compounds based on superhalogens and hyperhalogens.