title: Characterization of Actinide Bonding in Th(S(2)PMe(2))(4) by Synchrotron X-ray Diffraction.
abstract: Extensive synchrotron (28 K) and conventional sealed-tube (9 K) X-ray diffraction data have been collected on Th(S(2)PMe(2))(4). Modeling of the electron density of the complex shows the bonding is quite ionic with little diffuse f or d type bonding density. Furthermore a large polarization of the Th core is observed revealing some 5d-like involvement in the bonding. High-quality ab initio density functional calculations are not able to reproduce these features and instead predict rather covalent bonding with considerable 6d-5f mixing. The study suggests that this theoretical method exaggerates the covalent nature of actinide bonds. It is shown that the most direct measure of covalence-charge transfer and electron distributions-can be usefully estimated by X-ray diffraction even in this most unfavorable of cases, where many actinide core electrons are present. The use of very low temperature data is crucial in the study of heavy metal complexes in order to minimize systematic errors such as thermal diffuse scattering and anharmonicity. The fact that accurate synchrotron radiation diffraction data can be measured within days makes studies of compounds beyond the first transition series more frequently within reach.
authors.affiliation: Department of Chemistry, University of Aarhus, DK8000 Aarhus C, Denmark, Department of Chemistry, University of Toledo, Toledo, Ohio 43606, National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York 11973, and Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia.
authors.forename: Bo B.
authors.initials: BB
authors.lastname: Iversen
authors.forename: Finn K.
authors.initials: FK
authors.lastname: Larsen
authors.forename: Alan A.
authors.initials: AA
authors.lastname: Pinkerton
authors.forename: Anthony
authors.initials: A
authors.lastname: Martin
authors.forename: Alexander
authors.initials: A
authors.lastname: Darovsky
authors.forename: Philip A.
authors.initials: PA
authors.lastname: Reynolds