Cyclopentadienyl coordination induces unexpected ionic Am−N bonding in an americium bipyridyl complex

Abstract

Variations in bonding between trivalent lanthanides and actinides is critical for reprocessing spent nuclear fuel. The ability to tune bonding and the coordination environment in these trivalent systems is a key factor in identifying a solution for separating lanthanides and actinides. Coordination of 4,4′−bipyridine (4,4′−bpy) and trimethylsilylcyclopentadienide (Cp′) to americium introduces unexpectedly ionic Am−N bonding character and unique spectroscopic properties. Here we report the structural characterization of (Cp′3Am)2(μ − 4,4′−bpy) and its lanthanide analogue, (Cp′3Nd)2(μ − 4,4′−bpy), by single-crystal X-ray diffraction. Spectroscopic techniques in both solid and solution phase are performed in conjunction with theoretical calculations to probe the effects the unique coordination environment has on the electronic structure.

Expanding Transuranium Organoactinide Chemistry: Synthesis and Characterization of (Cp′3M)2(μ-4,4′-bpy) (M = Ce, Np, Pu)

“…25 All four reported structures possess greater M−N distances than those reported in the isostructural americium complex (Cp′ 3 Am) 2 (μ-4,4′-bpy). 19 It is important to note the influence the coordination environment can have on the bond lengths, again making a comparison to these unique systems difficult; however, the pyridine-based systems in the literature provide a similar M−N bond.…”

“…This aligns with the similar coordination environment of Cp′ 3 Ce(pyz) and (Cp′ 3 Am) 2 (μ-4,4′-bpy) but differs greatly from the higher symmetry in Cp′ 3 Np and Cp″ 3 Pu due to the change in the coordination environment from 4,4′-bpy. 19,20,26 Additional bonding comparison can be found in the Supporting Tables (Table S5).…”

“…Beginning with uranocene providing evidence for the participation of f-orbitals in bonding, and more recently, the characterization of a series of low-valent f-block oxidation states, metal–carbon bonding in the f-block has paved the way for understanding the fundamental organometallic chemistry of these elements. − Despite the significance of M–C bonding within the f-block, few organometallic studies have been completed utilizing transuranium elements. − The inherent air- and moisture-sensitivity or organometallic f-block complexes, in combination with the hazardous radiotoxicity and low available quantities of transuranium materials, lead to challenges in the synthesis and characterization of these complexes. However, recent synthetic advances and characterization methods in the field of organoactinide chemistry present opportunities for a suite of novel fundamental electronic and bonding properties with these elements, leading to improved charge transfer and separation applications. − …”

Carbene Complexes of Neptunium

“…The mixed-valent hexauranium ring complexes [{U III (BIPM TMS )} 3 {U IV (BIPM TMS )} 3 (μ-I) 3 (μ-η 6 :η 6 -C 6 H 5 R) 3 ] ((BIPM TMS ) 2– = {C­(PPh 2 NSiMe 3 ) 2 } 2– , a bis­(iminophosporano)­methanediide; R = H, CH 3 ), formally containing U III C bonds represent examples of U III -ligand multiple bonding, but the presence of noninnocent arene bridges clouds assignments . Although organotransuranium chemistry has begun to mature over the past 5 years or so, this still sparsely populated area remains dominated by π-bonded ligands, such as the venerable cyclopentadienyl, arene, and cyclooctatetraenyl ligand sets, − and only two σ-bonded hydrocarbyl Np complexes have been structurally validated. , …”

Th(IV) Bromide Complexes: A Homoleptic Aqua Ion and a Novel Th(H2O)4Br4 Structural Unit

“…Actinide solution and solid-state structural chemistry continues to garner significant attention. − This interest is motivated by fundamental needs such as understanding the role of the f-electrons in the behavior of heavy elements as well as challenges (and opportunities) in areas ranging from nuclear waste management to medicine. As an example, actinide structural chemistry has proved foundational to both our understanding of actinide behavior in the environment , and/or the development of actinide-based radiopharmaceuticals, both warranting insight into the conditions that drive the formation and stabilization of actinide structural units whether in solution or the solid state.…”