From π Bonds without σ Bonds to the Longest Metal–Metal Bond Ever: A Survey on Actinide–Actinide Bonding in Fullerenes

• Published in: Inorganic chemistry Vol. 59; no. 17; pp. 12608 - 12615
• Main Authors: Jaroš, Adam, Foroutan-Nejad, Cina, Straka, Michal
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 08-09-2020
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.0c01713

Actinide–actinide bonds are rare. Only a few experimental systems with An–An bonds have been described so far. Recent experimental characterization of the U2@I h (7)-C80 (J. Am. Chem. Soc. 2018, 140, 3907) system with one-electron two-center (OETC) U–U bonds as was predicted by some of us (Phys. Chem. Chem. Phys. 2015, 17, 24182) encourages the search for more examples of actinide–actinide bonding in fullerene cages. Here, we investigate actinide–actinide bonding in An2@D 5h (1)-C70, An2@I h (7)-C80, and An2@D 5h (1)-C90 (An = Ac–Cm) endohedral metallofullerenes (EMFs). Using different methods of the chemical bonding analysis, we show that most of the studied An2@C70 and An2@C80 systems feature one or more one-electron two-center actinide–actinide bonds. Unique bonding patterns are revealed in plutonium EMFs. The Pu2@I h (7)-C80 features two OETC Pu–Pu π bonds without any evidence of a corresponding σ bond. In the Pu2@D 5h (1)-C90 with r Pu–Pu = 5.9 Å, theory predicts the longest metal–metal bond ever described. Predicted systems are thermodynamically stable and should be, in principle, experimentally accessible, though radioactivity of studied metals may be a serious obstacle.