LAUSR

Synthesis of the first thorium-containing clusterfullerenes, ThC2@Cs(6)–C82 and ThC2@C2(5)–C82, is reported. These two novel actinide fullerene compounds were characterized by mass spectrometry, single-crystal X-ray diffraction crystallography, UV–vis–NIR spectroscopy, and theoretical calculations. Crystallographic studies reveal that the encapsulated ThC2 clusters in both Cs(6)–C82 and C2(5)–C82 feature a novel bonding structure with one thorium metal center connected by a C C unit, forming an isosceles triangular configuration, which has not been hitherto observed for endohedral fullerenes or for solid phase thorium carbides. Electronic structure calculations assign a formal electronic structure of [Th4+(C2)2−]2+@[C82]2−, with pronounced donation bonding from (C2)2− to Th4+, secondary backbonding from the fullerene to thorium and Th–C double bond character in both compounds. This work presents a new family of endohedral fullerenes, MC2@C2n−2, being unexpected isomers of MC2n, and provides broader understanding of thorium bonding.