Highly oxidized U(vi) within the smallest fullerene: gas-phase synthesis and computational study of boron-doped U@C27B

The smallest borafullerene U@C27B has been synthesized using a laser vaporization cluster source and detected as the most abundant species in the U@C2n−1B family. Density functional theory (DFT) calculations show that the U atom is placed just at the center of the cage interacting almost in the same way with all its atoms as if the cage were a 28-hapto ligand. Besides, the spin density is not at the metal, but distributed over the cage indicating that U is formally U(vi), even though it is not bonded to very electronegative atoms like O, F, N or Cl. All in all, we have synthesized a rather exotic radical that is another example of the distinctive host–guest chemistry that appears in endohedral metallofullerenes.