Main Group Metal–Actinide Magnetic Coupling and Structural Response Upon U⁴⁺ Inclusion Into Bi, Tl/Bi, or Pb/Bi Cages

The encapsulation of actinide ions in intermetalloid clusters has long been proposed but was never realized synthetically. We report the isolation and experimental, as well as quantum chemical, characterization of the uranium-centered clusters [U@Bi12]3–, [U@Tl2Bi11]3–, [U@Pb7Bi7]3–, and [U@Pb4Bi9]3–, upon reaction of (EE′Bi2)2– (E = Ga, Tl, E′ = Bi; E = E′ = Pb) and [U­(C5Me4H)3] or [U­(C5Me4H)3Cl] in 1,2-diaminoethane. For [U@Bi12]3–, magnetic susceptibility measurements rationalize an unprecedented antiferromagnetic coupling between a magnetic U4+ site and a unique radical Bi127– shell.