Divergent Stabilities of Tetravalent Cerium, Uranium, and Neptunium Imidophosphorane Complexes**

Kaitlyn S. Otte; Julie E. Niklas; Chad M. Studvick; Andrew C. Boggiano; John Bacsa; Ivan A. Popov; Henry S. La Pierre

doi:10.1002/anie.202306580

Divergent Stabilities of Tetravalent Cerium, Uranium, and Neptunium Imidophosphorane Complexes**

Kaitlyn S. Otte
, Julie E. Niklas
, Chad M. Studvick
, Andrew C. Boggiano
, John Bacsa
, Ivan A. Popov
, Henry S. La Pierre

Research output: Contribution to journal › Article › peer-review

21 Scopus citations

Abstract

The study of the redox chemistry of mid-actinides (U−Pu) has historically relied on cerium as a model, due to the accessibility of trivalent and tetravalent oxidation states for these ions. Recently, dramatic shifts of lanthanide 4+/3+ non-aqueous redox couples have been established within a homoleptic imidophosphorane ligand framework. Herein we extend the chemistry of the imidophosphorane ligand (NPC=[N=P^tBu(pyrr)₂]⁻; pyrr=pyrrolidinyl) to tetrahomoleptic NPC complexes of neptunium and cerium (1-M, 2-M, M=Np, Ce) and present comparative structural, electrochemical, and theoretical studies of these complexes. Large cathodic shifts in the M^4+/3+ (M=Ce, U, Np) couples underpin the stabilization of higher metal oxidation states owing to the strongly donating nature of the NPC ligands, providing access to the U^5+/4+, U^6+/5+, and to an unprecedented, well-behaved Np^5+/4+ redox couple. The differences in the chemical redox properties of the U vs. Ce and Np complexes are rationalized based on their redox potentials, degree of structural rearrangement upon reduction/oxidation, relative molecular orbital energies, and orbital composition analyses employing density functional theory.

Original language	English
Article number	e202306580
Journal	Angewandte Chemie - International Edition
Volume	62
Issue number	34
DOIs	https://doi.org/10.1002/anie.202306580
State	Published - Aug 21 2023
Externally published	Yes

Funding

This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Heavy Element Chemistry program under Award Number DE‐SC0019385 (K.S.O., J.E.N., A.C.B., H.S.L.). I.A.P. acknowledges computational resources at the Ohio Supercomputer Center and the ARCC HPC cluster at the University of Akron. We would like to acknowledge Cory Windorff (NMSU) and Tiffany Barker (GT) for their support during laboratory setup and transuranic synthesis, Alex Bredar (UNC) and Tim Paschkewitz (Pine Instruments) for their valuable insights on electrochemistry, and Tom Ferris (Anasazi Instruments) for assistance with BAPR NMR experiments. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Heavy Element Chemistry program under Award Number DE-SC0019385 (K.S.O., J.E.N., A.C.B., H.S.L.). I.A.P. acknowledges computational resources at the Ohio Supercomputer Center and the ARCC HPC cluster at the University of Akron. We would like to acknowledge Cory Windorff (NMSU) and Tiffany Barker (GT) for their support during laboratory setup and transuranic synthesis, Alex Bredar (UNC) and Tim Paschkewitz (Pine Instruments) for their valuable insights on electrochemistry, and Tom Ferris (Anasazi Instruments) for assistance with BAPR NMR experiments.

Keywords

Coordination Chemistry
Density Functional Theory
Electrochemistry
Ligand Design
Neptunium

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title = "Divergent Stabilities of Tetravalent Cerium, Uranium, and Neptunium Imidophosphorane Complexes**",

abstract = "The study of the redox chemistry of mid-actinides (U−Pu) has historically relied on cerium as a model, due to the accessibility of trivalent and tetravalent oxidation states for these ions. Recently, dramatic shifts of lanthanide 4+/3+ non-aqueous redox couples have been established within a homoleptic imidophosphorane ligand framework. Herein we extend the chemistry of the imidophosphorane ligand (NPC=[N=PtBu(pyrr)2]−; pyrr=pyrrolidinyl) to tetrahomoleptic NPC complexes of neptunium and cerium (1-M, 2-M, M=Np, Ce) and present comparative structural, electrochemical, and theoretical studies of these complexes. Large cathodic shifts in the M4+/3+ (M=Ce, U, Np) couples underpin the stabilization of higher metal oxidation states owing to the strongly donating nature of the NPC ligands, providing access to the U5+/4+, U6+/5+, and to an unprecedented, well-behaved Np5+/4+ redox couple. The differences in the chemical redox properties of the U vs. Ce and Np complexes are rationalized based on their redox potentials, degree of structural rearrangement upon reduction/oxidation, relative molecular orbital energies, and orbital composition analyses employing density functional theory.",

keywords = "Coordination Chemistry, Density Functional Theory, Electrochemistry, Ligand Design, Neptunium",

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AU - Otte, Kaitlyn S.

AU - Niklas, Julie E.

AU - Studvick, Chad M.

AU - Boggiano, Andrew C.

AU - Bacsa, John

AU - Popov, Ivan A.

AU - La Pierre, Henry S.

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AB - The study of the redox chemistry of mid-actinides (U−Pu) has historically relied on cerium as a model, due to the accessibility of trivalent and tetravalent oxidation states for these ions. Recently, dramatic shifts of lanthanide 4+/3+ non-aqueous redox couples have been established within a homoleptic imidophosphorane ligand framework. Herein we extend the chemistry of the imidophosphorane ligand (NPC=[N=PtBu(pyrr)2]−; pyrr=pyrrolidinyl) to tetrahomoleptic NPC complexes of neptunium and cerium (1-M, 2-M, M=Np, Ce) and present comparative structural, electrochemical, and theoretical studies of these complexes. Large cathodic shifts in the M4+/3+ (M=Ce, U, Np) couples underpin the stabilization of higher metal oxidation states owing to the strongly donating nature of the NPC ligands, providing access to the U5+/4+, U6+/5+, and to an unprecedented, well-behaved Np5+/4+ redox couple. The differences in the chemical redox properties of the U vs. Ce and Np complexes are rationalized based on their redox potentials, degree of structural rearrangement upon reduction/oxidation, relative molecular orbital energies, and orbital composition analyses employing density functional theory.

KW - Coordination Chemistry

KW - Density Functional Theory

KW - Electrochemistry

KW - Ligand Design

KW - Neptunium

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ER -

Divergent Stabilities of Tetravalent Cerium, Uranium, and Neptunium Imidophosphorane Complexes**

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Keywords

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