Redox-Promoted Reactivity of Uranium, Neptunium, and Plutonium Diamide Complexes
- 1Chemical Sciences and Engineering Division
- 2Argonne National Laboratory
Abstract
The chemically active 5 f orbitals of the early actinides give rise to a number of accessible oxidation states, as well as contribute to complex redox behavior that is sensitive to changes in the coordination environment of the metal. Understanding how these electronic and coordination effects translate into structural transformation remains a central challenge in fundamental actinide chemistry. Herein, we present a crystallographic and spectroscopic investigation of redox-promoted reactivity in uranium, neptunium, and plutonium complexes supported by malonamide and diglycolamide ligands, which provide flexible O-donor coordination environments for investigating structural chemistry of early actinides as a function of the oxidation state. A series of molecular [An VI O 2 (ma)(NO 3 ) 2 ], [An VI O 2 (tmma)(NO 3 ) 2 ], and [An VI O 2 (tmdga) 2 ](NO 3 ) 2 complexes across the U−Np−Pu series has been prepared and structurally characterized, providing a platform for examining chemical transformations induced by ligand degradation and electron transfer (ma = malonamide; tmma = N,N,N′,N′ -tetramethylmalonamide; tmdga = N,N,N′,N′- tetramethyldiglycolamide). Aging these complexes in acidic media leads to the formation of unexpected products spanning multiple oxidation states, including oxalate-bridged actinyl dimers generated through oxidative degradation of diglycolamide ligands, mixed-valent Pu(IV)/Pu(VI) molecular ion pairs, and neptunium species that evolve from monomeric Np(VI) complexes to mixed-valent Np(V)/Np(IV) assemblies featuring Np V =O yl −Np IV actinyl–actinide interactions before complete reduction to Np(IV) products. Complementary single-crystal Raman spectroscopy provides vibrational fingerprints of the actinyl units and coordinated ligands, supporting the structural assignments and enabling comparisons across the U–Np–Pu series. These results demonstrate that diamide ligands may serve as both coordination platforms and active participants in redox chemistry, giving rise to reaction pathways that generate previously inaccessible molecular species.
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BibTeX
@misc{kravchuk2026redoxpromoted,
title = {{Redox-Promoted Reactivity of Uranium, Neptunium, and Plutonium Diamide Complexes}},
author = {Dmytro V. Kravchuk},
howpublished = {ChemRxiv},
year = {2026},
month = sep,
doi = {10.26434/chemrxiv.15008828/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008828/v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Redox-Promoted Reactivity of Uranium, Neptunium, and Plutonium Diamide Complexes
AU - Dmytro V. Kravchuk
PY - 2026
DA - 2026/09/14
PB - ChemRxiv
DO - 10.26434/chemrxiv.15008828/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008828/v1
AB - The chemically active 5 f orbitals of the early actinides give rise to a number of accessible oxidation states, as well as contribute to complex redox behavior that is sensitive to changes in the coordination environment of the metal. Understanding how these electronic and coordination effects translate into structural transformation remains a central challenge in fundamental actinide chemistry. Herein, we present a crystallographic and spectroscopic investigation of redox-promoted reactivity in uranium, neptunium, and plutonium complexes supported by malonamide and diglycolamide ligands, which provide flexible O-donor coordination environments for investigating structural chemistry of early actinides as a function of the oxidation state. A series of molecular [An VI O 2 (ma)(NO 3 ) 2 ], [An VI O 2 (tmma)(NO 3 ) 2 ], and [An VI O 2 (tmdga) 2 ](NO 3 ) 2 complexes across the U−Np−Pu series has been prepared and structurally characterized, providing a platform for examining chemical transformations induced by ligand degradation and electron transfer (ma = malonamide; tmma = N,N,N′,N′ -tetramethylmalonamide; tmdga = N,N,N′,N′- tetramethyldiglycolamide). Aging these complexes in acidic media leads to the formation of unexpected products spanning multiple oxidation states, including oxalate-bridged actinyl dimers generated through oxidative degradation of diglycolamide ligands, mixed-valent Pu(IV)/Pu(VI) molecular ion pairs, and neptunium species that evolve from monomeric Np(VI) complexes to mixed-valent Np(V)/Np(IV) assemblies featuring Np V =O yl −Np IV actinyl–actinide interactions before complete reduction to Np(IV) products. Complementary single-crystal Raman spectroscopy provides vibrational fingerprints of the actinyl units and coordinated ligands, supporting the structural assignments and enabling comparisons across the U–Np–Pu series. These results demonstrate that diamide ligands may serve as both coordination platforms and active participants in redox chemistry, giving rise to reaction pathways that generate previously inaccessible molecular species.
ER -