Americium is an actinide and the first transplutonium element. Its long‐lived isotope ²⁴³Am is most suitable for synthetic chemistry. However, ²⁴³Am is both scarce and highly radioactive, which makes it difficult to work with. There are examples of organometallic actinide compounds. However, no transplutonium organometallic compound had been characterized using single-crystal X-ray diffraction so far.

Enrique R. Batista, Andrew J. Gaunt, Stosh A. Kozimor, Ping Yang, Los Alamos National Laboratory, NM, USA, William J. Evans, University of California, Irvine, USA, and colleagues have synthesized the Am³⁺ organometallic complex [Am(C₅Me₄H)₃] (pictured). Due to the scarcity of  ²⁴³Am, small-scale optimization was performed on lanthanide and actinide analogues to enable successful work with only 5 mg of Am.

The team started from ²⁴³AmO₂, which was dissolved in hydrochloric acid and dried under an argon stream to give an AmCl₃ residue. Dimethyl ether (DME) and trimethylsilyl chloride (TMSCl) were added to give a putative AmCl₃(DME)_n reactant. Potassium tetramethylcyclopentadienyl was added to give the desired product in 49 % yield as an orange crystalline solid (pictured). The complex was characterized by single‐crystal X‐ray diffraction and is isostructural with other [M(C₅Me₄H)₃] complexes.

• [Am(C₅Me₄H)₃]: An Organometallic Americium Complex,
  Conrad A. P. Goodwin, Jing Su, Thomas E. Albrecht-Schmitt, Anastasia V. Blake, Enrique R. Batista, Scott R. Daly, Stefanie Dehnen, William J. Evans, Andrew J. Gaunt, Stosh A. Kozimor, Niels Lichtenberger, Brian L. Scott, Ping Yang,
  Angew. Chem. Int. Ed. 2019.
  https://doi.org/10.1002/anie.201905225