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Characterizing pressure-induced uranium C-H agostic bonds.

  • Author(s): Arnold, Polly L
  • Prescimone, Alessandro
  • Farnaby, Joy H
  • Mansell, Stephen M
  • Parsons, Simon
  • Kaltsoyannis, Nikolas
  • et al.
Abstract

The diuranium(III) compound [UN''2]2(μ-η(6):η(6)-C6H6) (N''=N(SiMe3)2) has been studied using variable, high-pressure single-crystal X-ray crystallography, and density functional theory . In this compound, the low-coordinate metal cations are coupled through π- and δ-symmetric arene overlap and show close metal-CH contacts with the flexible methyl CH groups of the sterically encumbered amido ligands. The metal-metal separation decreases with increasing pressure, but the most significant structural changes are to the close contacts between ligand CH bonds and the U centers. Although the interatomic distances are suggestive of agostic-type interactions between the U and ligand peripheral CH groups, QTAIM (quantum theory of atoms-in-molecules) computational analysis suggests that there is no such interaction at ambient pressure. However, QTAIM and NBO analyses indicate that the interaction becomes agostic at 3.2 GPa.

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