A terminal neptunium(V)–mono(oxo) complex

• Published in: Nature chemistry Vol. 14; no. 3; pp. 342 - 349
• Main Authors: Dutkiewicz, Michał S., Goodwin, Conrad A. P., Perfetti, Mauro, Gaunt, Andrew J., Griveau, Jean-Christophe, Colineau, Eric, Kovács, Attila, Wooles, Ashley J., Caciuffo, Roberto, Walter, Olaf, Liddle, Stephen T.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01-03-2022; Nature Publishing Group
• Subjects: 639/638/263; 639/638/911; Analytical Chemistry; Biochemistry; Chemical bonds; Chemical synthesis; Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Inorganic Chemistry; Ligands; Neptunium; Organic Chemistry; Oxidation; Physical Chemistry; Plutonium; Uranium; Valence
• ISSN: 1755-4330; 1755-4349
• DOI: 10.1038/s41557-021-00858-0

Neptunium was the first actinide element to be artificially synthesized, yet, compared with its more famous neighbours uranium and plutonium, is less conspicuously studied. Most neptunium chemistry involves the neptunyl di(oxo)-motif, and transuranic compounds with one metal–ligand multiple bond are rare, being found only in extended-structure oxide, fluoride or oxyhalide materials. These combinations stabilize the required high oxidation states, which are otherwise challenging to realize for transuranic ions. Here we report the synthesis, isolation and characterization of a stable molecular neptunium(V)–mono(oxo) triamidoamine complex. We describe a strong Np≡O triple bond with dominant 5
f
-orbital contributions and
σ
u
 > 
π
u
energy ordering, akin to terminal uranium-nitrides and di(oxo)-actinyls, but not the uranium–mono(oxo) triple bonds or other actinide multiple bonds reported so far. This work demonstrates that molecular high-oxidation-state transuranic complexes with a single metal–ligand bond can be stabilized and studied in isolation.
Neptunium was the first actinide to be artificially synthesized, yet its chemistry has remained relatively unexplored. Most neptunium chemistry involves the neptunyl di(oxo) motif, and transuranic compounds with only one metal–ligand multiple bond are generally rare. Now, a stable complex of neptunium in the +5 oxidation state has been isolated that features a single terminal Np–O multiple bond.