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Issue 4, 2017
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Reduction chemistry of neptunium cyclopentadienide complexes: from structure to understanding

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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

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Publication details

The article was received on 04 Jan 2017, accepted on 27 Jan 2017 and first published on 30 Jan 2017


Article type: Edge Article
DOI: 10.1039/C7SC00034K
Citation: Chem. Sci., 2017,8, 2553-2561
  • Open access: Creative Commons BY license
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    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

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