title: Characterizing pressure-induced uranium C-H agostic bonds.
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.
authors.affiliation: EaStCHEM School of Chemistry, University of Edinburgh, The King's Buildings, Edinburgh, EH9 3FJ (UK). Polly.Arnold@ed.ac.uk.
authors.forename: Polly L
authors.initials: PL
authors.lastname: Arnold
authors.affiliation: EaStCHEM School of Chemistry, University of Edinburgh, The King's Buildings, Edinburgh, EH9 3FJ (UK).|Current address: Department of Chemistry, University of Basel, Spitalstrasse 51, 4056 Basel (Switzerland).
authors.forename: Alessandro
authors.initials: A
authors.lastname: Prescimone
authors.affiliation: EaStCHEM School of Chemistry, University of Edinburgh, The King's Buildings, Edinburgh, EH9 3FJ (UK).|Current address: Department of Chemistry, Imperial College London, South Kensington Campus, London, SW7 2AZ (UK).
authors.forename: Joy H
authors.initials: JH
authors.lastname: Farnaby
authors.affiliation: EaStCHEM School of Chemistry, University of Edinburgh, The King's Buildings, Edinburgh, EH9 3FJ (UK).|Current address: Institute of Chemical Sciences, Heriot-Watt University, Edinburgh, EH14 4AS (UK).
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Mansell
authors.affiliation: EaStCHEM School of Chemistry, University of Edinburgh, The King's Buildings, Edinburgh, EH9 3FJ (UK). Simon.Parsons@ed.ac.uk.
authors.forename: Simon
authors.initials: S
authors.lastname: Parsons
authors.affiliation: Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ (UK). N.Kaltsoyannis@ucl.ac.uk.
authors.forename: Nikolas
authors.initials: N
authors.lastname: Kaltsoyannis
keywords: X-ray diffraction; actinides; density functional calculations; high-pressure chemistry; uranium