Fullerene cage stabilises first yttrium–yttrium single bond

Theory had predicted a direct single bond between two yttrium centres but researchers had struggled to realise it experimentally. Now, scientists in China have become the first to make the elusive bond as part of an endohedral metallofullerene.

Xing Lu from Huazhong University of Science and Technology and colleagues used the stabilising effect of a fullerene cage to assist them in making the yttrium–yttrium bond. They prepared the metallofullerenes by arc discharge of a graphite/Y₂O₃ mixture and separated the resulting products by HPLC. This allowed the researchers to observe the encapsulated metals by x-ray crystallography.

Measured bond distances indicate that a single bond forms between two divalent yttrium sites. Interestingly, the direct yttrium–yttrium interaction was observed only in relatively small cages (C₈₂) with yttrium carbide clusters forming in larger cages (C_86-92).