Identification of oxidation state +1 in a molecular uranium complex
Barluzzi, Luciano; Giblin, Sean R.; Mansikkamäki, Akseli; Layfield, Richard A. (2022-09-28)
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. https://doi.org/10.1021/jacs.2c06519
© 2022 The Authors. Published by American Chemical Society.
https://creativecommons.org/licenses/by/4.0/
https://urn.fi/URN:NBN:fi-fe2022102462783
Tiivistelmä
Abstract
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-C₅ⁱPr₅)₂] and the uranium(III) metallocene [IU(η⁵-C₅ⁱPr₅)₂] can be reduced by potassium graphite in the presence of 2.2.2-cryptand to the uranium(I) metallocene [U(η⁵-C₅ⁱPr₅)₂]⁻ (𝟏) (C₅ⁱPr₅ = 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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