Dispersion Forces Drive the Formation of Uranium-Alkane Adducts

Julie Jung; Sascha T Löffler; Jan Langmann; Frank W Heinemann; Eckhard Bill; Giovanni Bistoni; Wolfgang Scherer; Mihail Atanasov; Karsten Meyer; Frank Neese

doi:10.1021/jacs.9b10620

Dispersion Forces Drive the Formation of Uranium-Alkane Adducts

J Am Chem Soc. 2020 Jan 29;142(4):1864-1870. doi: 10.1021/jacs.9b10620. Epub 2020 Jan 13.

Authors

Julie Jung^{1

2}, Sascha T Löffler³, Jan Langmann⁴, Frank W Heinemann³, Eckhard Bill⁵, Giovanni Bistoni¹, Wolfgang Scherer⁴, Mihail Atanasov^{1

6}, Karsten Meyer³, Frank Neese¹

Affiliations

¹ Department of Molecular Theory and Spectroscopy , Max-Planck Institute for Kohlenforschung , Kaiser Wilhelm-Platz-1 , 45470 Mülheim-an-der-Ruhr , Germany.
² Theoretical Division , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States.
³ Inorganic Chemistry, Department of Chemistry and Pharmacy , Friedrich-Alexander-University Erlangen-Nürnberg (FAU) , Egerlandstrasse 1 , 91058 Erlangen , Germany.
⁴ Lehrstuhl für Chemische Physik und Materialwissenschaften , Institut für Physik, Universität Augsburg , Universitätsstraße 1 , 86159 Augsburg , Germany.
⁵ Department of Molecular Theory and Spectroscopy , Max-Planck Institute for Chemical Energy Conversion , Stiftstrasse 34-36 , 45470 Mülheim-an-der-Ruhr , Germany.
⁶ Institute of General and Inorganic Chemistry , Bulgarian Academy of Sciences , Akad. Georgi Bontchev Street 11 , 1113 Sofia , Bulgaria.

PMID: 31884789
DOI: 10.1021/jacs.9b10620

Abstract

Single-crystal cryogenic X-ray diffraction at 6 K, electron paramagnetic resonance spectroscopy, and correlated electronic structure calculations are combined to shed light on the nature of the metal-tris(aryloxide) and η²-H, C metal-alkane interactions in the [((^t·BuArO)₃tacn)U^III(^Mecy-C6)]·(^Mecy-C6) adduct. An analysis of the ligand field experienced by the uranium center using ab initio ligand field theory in combination with the angular overlap model yields rather unusual U-O_ArO and U-N_tacn bonding parameters for the metal-tris(aryloxide) interaction. These parameters are incompatible with the concept of σ and π metal-ligand overlap. For that reason, it is deduced that metal-ligand bonding in the [((^t·BuArO)₃tacn)U^III] moiety is predominantly ionic. The bonding interaction within the [((^t·BuArO)₃tacn)U^III] moiety is shown to be dispersive in nature and essentially supported by the upper-rim ^tBu groups of the (^t·BuArO)₃tacn^3- ligand. Our findings indicate that the axial alkane molecule is held in place by the guest-host effect rather than direct metal-alkane ionic or covalent interactions.