actinocene

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 ) bound to an actinide-metal center (An) in the oxidation state IV, resulting in the general formula An(C8H8)2.

== Characterised actinocenes == {| class="wikitable" !Name !Formula !AnIV centre !First synthesis !Crystal colour !An–COT distance (Å) !Space group |- |Thorocene |Th(C8H8)2 |Th |1969 | style='background: #FFFF00' |bright yellow |2.004 |P21/n |- |Protactinocene |Pa(C8H8)2 |Pa |1974 | style='background: #E9D66B'|yellowish |1.933 (calculated) |P21/n |- |Uranocene |U(C8H8)2 |U |1968 | style='background: #00A550'|deep green |1.926 |P21/n |- |Neptunocene |Np(C8H8)2 |Np |1970 | style='background: #B8860B'|yellow-brown |1.909 |P21/n |- |Plutonocene |Pu(C8H8)2 |Pu |1970 | style='background: #C51E3A'|dark red |1.898 |I2/m |- | Berkelocene |Bk(C14H16)2 |Bk |2025 | style='background: #3F00FF'|indigo |1.88 |P |} The most studied actinocene is uranocene, U(C8H8)2, which in 1968 was the first member of this family to be synthesised and is still viewed as the archetypal example. Other actinocenes that have been synthesised are protactinocene (Pa(C8H8)2), thorocene (Th(C8H8)2), neptunocene (Np(C8H8)2), and plutonocene (Pu(C8H8)2). Especially the latter two, neptunocene and plutonocene, have not been extensively studied experimentally since the 1980s because of the radiation hazard they pose. Berkelocene (with a modified COT ligand) was synthesised in 2025, the first actinocene with a new actinide in over 50 years.