Hexacoordinate Actinide(IV) Compounds: Benchmark Complexes for Magnetism and Electronic Structure Analysis

Journal of the American Chemical Society

Abstract

Abstract Two series of actinide tetrachloride complexes with the monodentate carboxylic amide ligands phthalimidine (H-phthal) and 2-pyridone (HPyO) of the general formula [AnIVCl4(L)2] (An = U, Np, Pu) were synthesized and characterized in the solid state and in solution. SC-XRD analysis revealed an octahedral coordination environment with trans orientation of either H-phthal or HPyO in all cases, with and without THF molecules hydrogen-bonded to the NH group of the ligands. In the case of [NpCl4(H-phthal)2], the absence of THF leads to a significant distortion of the coordination geometry around the metal, including the shortest Np–Cl bonds observed so far (2.4394(8) Å). A quantum chemical bonding analysis (QTAIM) showed that the main bonding interaction is found between the actinide and chloride ligands, with the amides rather loosely bound. Despite their unusually low coordination number, the complexes were found to be stable, even in coordinating solvents. This allowed for an in-depth analysis of their 1H and 13C NMR spectroscopy. Due to their pseudoD4h symmetry in the first coordination sphere, these complexes are excellent model systems to analyze their electronic structure and magnetic properties. We applied SQUID magnetometry to extract magnetic properties (μeff) and crystal field parameters ( Bqk, Wybourne) in combination with quantum chemical calculations, which allows for the comprehensive description of the electronic ground state from an experimental and theoretical point of view.

Authors 13

1. Till Erik Sawallisch

   Helmholtz-Zentrum Dresden-Rossendorf

   Affiliation as printed

   Helmholtz-Zentrum Dresden − Rossendorf , , Bautzner Landstraße 400 , ,

2. Dennis Grödler

   Helmholtz-Zentrum Dresden-Rossendorf

   Affiliation as printed

   Helmholtz-Zentrum Dresden − Rossendorf , , Bautzner Landstraße 400 , ,

3. Adrian Näder

   Helmholtz-Zentrum Dresden-Rossendorf

   Affiliation as printed

   Helmholtz-Zentrum Dresden − Rossendorf , , Bautzner Landstraße 400 , ,

4. Clara L. Silva

   Helmholtz-Zentrum Dresden-Rossendorf · European Synchrotron Radiation Facility

   Affiliation as printed

   Helmholtz-Zentrum Dresden − Rossendorf , , Bautzner Landstraße 400 , ,

   The Rossendorf Beamline at ESRF − The European Synchrotron , CS40220 , ,

5. Peter Kaden

   Helmholtz-Zentrum Dresden-Rossendorf

   Affiliation as printed

   Helmholtz-Zentrum Dresden − Rossendorf , , Bautzner Landstraße 400 , ,

6. Michael Patzschke

   Helmholtz-Zentrum Dresden-Rossendorf

   Affiliation as printed

   Helmholtz-Zentrum Dresden − Rossendorf , , Bautzner Landstraße 400 , ,

7. Lucia Amidani

   Helmholtz-Zentrum Dresden-Rossendorf · European Synchrotron Radiation Facility

   Affiliation as printed

   Helmholtz-Zentrum Dresden − Rossendorf , , Bautzner Landstraße 400 , ,

   The Rossendorf Beamline at ESRF − The European Synchrotron , CS40220 , ,

8. Kristina O. Kvashnina

   Helmholtz-Zentrum Dresden-Rossendorf · European Synchrotron Radiation Facility

   Affiliation as printed

   Helmholtz-Zentrum Dresden − Rossendorf , , Bautzner Landstraße 400 , ,

   The Rossendorf Beamline at ESRF − The European Synchrotron , CS40220 , ,

9. Solveig Pospiech

   Helmholtz-Zentrum Dresden-Rossendorf

   Affiliation as printed

   Helmholtz-Zentrum Dresden − Rossendorf , , Bautzner Landstraße 400 , ,

10. Jan van Leusen Aachen

    RWTH Aachen University

    Affiliation as printed

    RWTH Aachen University , , Landoltweg 1 , ,

11. Moritz Schmidt

    Helmholtz-Zentrum Dresden-Rossendorf · Brandenburg University of Technology Cottbus-Senftenberg

    Affiliation as printed

    Brandenburg University of Technology Cottbus-Senftenberg , , ,

    Helmholtz-Zentrum Dresden − Rossendorf , , Bautzner Landstraße 400 , ,

12. Thorsten Stumpf

    Helmholtz-Zentrum Dresden-Rossendorf

    Affiliation as printed

    Helmholtz-Zentrum Dresden − Rossendorf , , Bautzner Landstraße 400 , ,

13. Robert Gericke

    Helmholtz-Zentrum Dresden-Rossendorf

    Affiliation as printed

    Helmholtz-Zentrum Dresden − Rossendorf , , Bautzner Landstraße 400 , ,