University of Oulu

Barluzzi, L., Giblin, S. R., Mansikkamäki, A., & Layfield, R. A. (2022). Identification of oxidation state +1 in a molecular uranium complex. Journal of the American Chemical Society, 144(40), 18229–18233.

Identification of oxidation state +1 in a molecular uranium complex

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Author: Barluzzi, Luciano1; Giblin, Sean R.2; Mansikkamäki, Akseli3;
Organizations: 1Department of Chemistry, School of Life Sciences, University of Sussex, Brighton BN1 9JQ, U.K.
2School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA, U.K.
3NMR Research Group, University of Oulu, P.O. Box 8000, FI-90014 Oulu, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 3.1 MB)
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Language: English
Published: American Chemical Society, 2022
Publish Date: 2022-10-24


The concept of oxidation state plays a fundamentally important role in defining the chemistry of the elements. In the f block of the periodic table, well-known oxidation states in compounds of the lanthanides include 0, +2, +3 and +4, and oxidation states for the actinides range from +7 to +2. Oxidation state +1 is conspicuous by its absence from the f-block elements. Here we show that the uranium(II) metallocene [U(η⁵-C₅Pr₅)₂] and the uranium(III) metallocene [IU(η⁵-C₅Pr₅)₂] can be reduced by potassium graphite in the presence of 2.2.2-cryptand to the uranium(I) metallocene [U(η⁵-C₅Pr₅)₂]− (𝟏) (C₅Pr₅ = pentaisopropylcyclopentadienyl) as the salt of [K(2.2.2-cryptand)]⁺. An X-ray crystallographic study revealed that 𝟏 has a bent metallocene structure, and theoretical studies and magnetic measurements confirmed that the electronic ground state of uranium(I) adopts a 5f³(7s/6dz²)¹(6dx²–y²/6dxy)¹ configuration. The metal–ligand bonding in 𝟏 consists of contributions from uranium 5f, 6d, and 7s orbitals, with the 6d orbitals engaging in weak but non-negligible covalent interactions. Identification of the oxidation state +1 for uranium expands the range of isolable oxidation states for the f-block elements and potentially signposts a synthetic route to this elusive species for other actinides and the lanthanides.

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Series: Journal of the American Chemical Society
ISSN: 0002-7863
ISSN-E: 1520-5126
ISSN-L: 0002-7863
Volume: 144
Issue: 40
Pages: 18229 - 18233
DOI: 10.1021/jacs.2c06519
Type of Publication: A1 Journal article – refereed
Field of Science: 116 Chemical sciences
114 Physical sciences
Funding: The authors thank the EPSRC (Grants EP/V003089/1 and EP/V046659/1) and the Academy of Finland (Grant 332294) for funding, the U.K. National Crystallography Service for providing X-ray diffraction data on [K(2.2.2-crypt)][1] (EPSRC Grant EP/W02098X/1), Dr. R. Thorogate for providing access to a PPMS at the London Centre for Nanotechnology, Dr. A. Collauto at the Centre for Pulse EPR at Imperial College London for providing EPR data (EPSRC Grant EP/T031425/1), the University of Oulu (Kvantum Institute), and the CSC-IT Center for Science in Finland and the Finnish Grid and Cloud Infrastructure (persistent identifier urn:nbn:fi:research-infras-2016072533).
Academy of Finland Grant Number: 332294
Detailed Information: 332294 (Academy of Finland Funding decision)
Copyright information: © 2022 The Authors. Published by American Chemical Society.