Actinocenes are a family of organoactinide compounds consisting of metallocenes containing elements from the actinide series.
They typically have a sandwich structure with two dianionic cyclooctatetraenyl ligands (COT2-, which is C8H2−8) bound to an actinide-metal center (An) in the oxidation state IV, resulting in the general formula An(C8H8)2.
[2][4] Other actinocenes that have been synthesised are protactinocene[5] (Pa(C8H8)2), thorocene[6] (Th(C8H8)2), neptunocene[7] (Np(C8H8)2), and plutonocene[8][9] (Pu(C8H8)2).
[9][10] Computational chemistry methods indicate bonding with a large covalent character resulting mainly from the mixing of actinide 6d orbitals with ligand π-orbitals, with a smaller interaction involving the actinide 5f and ligand π-orbitals.
Analogous sandwiched M(C8H8)2 compounds also exist for lanthanides M = Nd, Tb, and Yb, but therein the bonding is mostly ionic rather than covalent (see lanthanocenes).