Redox-active metal-metal bonds between lanthanides in dimetallofullerenes

The empty space inside a fullerene cage can be filled with a variety of species, including metal dimers. Encapsulation of Sc-2, Y-2, or lanthanide dimers leads to dimetallofullerenes featuring metal-metal bonding molecular orbital. Such an orbital can be either HOMO or LUMO of the dimetallofullerene molecule. In certain cases, single-occupied metal-metal bonding orbital can be also stabilized. This review is focused on redox processes involving variation of the electron population of metal-metal bonding orbitals in dimetallofullerenes.