Issue 4, 2017

Reduction chemistry of neptunium cyclopentadienide complexes: from structure to understanding

Abstract

Neptunium complexes in the formal oxidation states II, III, and IV supported by cyclopentadienyl ligands are explored, and significant differences between Np and U highlighted as a result. A series of neptunium(III) cyclopentadienyl (Cp) complexes [Np(Cp)3], its bis-acetonitrile adduct [Np(Cp)3(NCMe)2], and its KCp adduct K[Np(Cp)4] and [Np(Cp′)3] (Cp′ = C5H4SiMe3) have been made and characterised providing the first single crystal X-ray analyses of NpIII Cp complexes. In all NpCp3 derivatives there are three Cp rings in η5-coordination around the NpIII centre; additionally in [Np(Cp)3] and K[Np(Cp)4] one Cp ring establishes a μ-η1-interaction to one C atom of a neighbouring Np(Cp)3 unit. The solid state structure of K[Np(Cp)4] is unique in containing two different types of metal–Cp coordination geometries in the same crystal. NpIII(Cp)4 units are found exhibiting four units of η5-coordinated Cp rings like in the known complex [NpIV(Cp)4], the structure of which is now reported. A detailed comparison of the structures gives evidence for the change of ionic radii of ca. −8 pm associated with change in oxidation state between NpIII and NpIV. The rich redox chemistry associated with the syntheses is augmented by the reduction of [Np(Cp′)3] by KC8 in the presence of 2.2.2-cryptand to afford a neptunium(II) complex that is thermally unstable above −10 °C like the UII and ThII complexes K(2.2.2-cryptand)[Th/U(Cp′)3]. Together, these spontaneous and controlled redox reactions of organo-neptunium complexes, along with information from structural characterisation, show the relevance of organometallic Np chemistry to understanding fundamental structure and bonding in the minor actinides.

Graphical abstract: Reduction chemistry of neptunium cyclopentadienide complexes: from structure to understanding

Supplementary files

Article information

Article type
Edge Article
Submitted
04 Janv. 2017
Accepted
27 Janv. 2017
First published
30 Janv. 2017
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2017,8, 2553-2561

Reduction chemistry of neptunium cyclopentadienide complexes: from structure to understanding

M. S. Dutkiewicz, C. Apostolidis, O. Walter and P. L. Arnold, Chem. Sci., 2017, 8, 2553 DOI: 10.1039/C7SC00034K

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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