Metal clusters that can encapsulate hydride ions might offer a new hydrogen storage strategy. 

Hydrogen gas is bulky and highly flammable. Its successful application in new fuel technologies depends on its safe and compact storage. 

'Because of drawbacks associated with the storage of pure hydrogen, effort is now being directed towards chemical storage in solid media and also towards the storage of its precursor: the hydride ion,' said Andrew Wheatley of the University of Cambridge, UK. 

Wheatley and colleagues found that a cluster of eight lithium atoms, capped with amide ligands, forms a cubic structure that can readily house a hydride ion. The bonding mode of the hydride ion within the cluster can be changed by changing the organic ligand.

Varying both the metal and the organic amide ligand, said Wheatley, could lead to new polyhedral structures with the potential to encapsulate more hydride, or different anions altogether. 

'The future challenge of testing whether these hydridic ions can source hydrogen - and do so reversibly - means that there is plenty of scope for future work in this field,' added Wheatley. 

Alan Holder