Small-Scale Metal-Based Syntheses of Lanthanide Iodide, Amide, and Cyclopentadienyl Complexes as Analogues for Transuranic Reactions

Abstract

Small-scale reactions of the Pu analogues La, Ce, and Nd have been explored in order to optimize reaction conditions for milligram scale reactions of radioactive plutonium starting from the metal. Oxidation of these lanthanide metals with iodine in ether and pyridine has been studied, and LnI(EtO) (1-Ln; x = 0.75-1.9) and LnI(py) (2-Ln; py = pyridine, NCH) have been synthesized on scales ranging from 15 mg to 2 g. The THF adducts LnI(THF) (3-Ln) were synthesized by dissolving 1-Ln in THF. The viability of these small-scale samples as starting materials for amide and cyclopentadienyl f-element complexes was tested by reacting KN(SiMe), KCp' (Cp' = CHSiMe), KCp'' (Cp'' = CH(SiMe)-1,3), and KCMeH with 1-Ln generated in situ. These reactions produced Ln[N(SiMe)] (4-Ln), Cp'Ln (5-Ln), Cp″Ln (6-Ln), and (CMeH)Ln (7-Ln), respectively. Small-scale samples of Cp'Ce (5-Ce) and Cp'Nd (5-Nd) were reduced with potassium graphite (KC) in the presence of 2.2.2-cryptand to check the viability of generating the crystallographically characterizable Ln complexes [K(2.2.2-cryptand)][Cp'Ln] (8-Ln; Ln = Ce, Nd).

[Am(C5Me4H)3]: An Organometallic Americium Complex

“…The range of out‐of‐the‐C 5 ‐plane displacements of the Me‐groups in 1 is 0.09(4)–0.24(4) Å, with the larger displacements being for C7 and C8. These metrics provide no evidence of steric oversaturation and compare well with those of 2‐Nd and are shorter than for 2‐U …”

“…Reports that [Ln(Cp tet ) 3 ] (Cp tet =C 5 Me 4 H) complexes were isolated as single crystals on small scales led us to choose Cp tet as a candidate . Optimization of the synthetic protocol was conducted by small scale synthesis of [Ce(Cp tet ) 3 ] ( 2‐Ce ) as a surrogate for [Am(Cp tet ) 3 ] ( 1 ) . It was determined that 2‐Ce could be isolated as single‐crystals, in high‐yield, within a few hours, utilizing Ce 3+ in acidic (HCl) aqueous solution as the precursor (to mimic the form of available 243 Am).…”

Computational Investigation of the Bonding in [(η5–Cp′)3(η1–Cp′)M]1– (M = Pu, U, Ce)

“…First, many studies have concluded that the covalent contribution to bonding in the actinide series peaks at either U or Pu. , Second, cerium is commonly used as a nonradioactive analogue for plutonium. Thus, understanding how it differs from actinides is crucial for detailing how 4f and 5f elements diverge in terms of their electronic structures. , …”

“…Thus, understanding how it differs from actinides is crucial for detailing how 4f and 5f elements diverge in terms of their electronic structures. 99,100 ■ COMPUTATIONAL DETAILS Geometries. The structures of [(η 5 67 U, 62 and Ce 66 ) were obtained using the coordinates of the experimentally determined crystal structure from the crystallographic information file (CIF) without further optimization to conserve the constraints imposed by the crystal packing.…”

Advancing understanding of actinide(iii) (Ac, Am, Cm) aqueous complexation chemistry

“…Consider numerous reports published in journals focused on characterizing "simple" starting materials, those that need to be better understood because of widespread use. [19][20][21][22][23] These modest contributions are highly cited and foundational. From that perspective, we drew analogy to actinide (NH 4 )O 2 CMe (aq) :HO 2 CMe (aq) buffered stock solutions and embarked to change the current state of affairs.…”