title: Uranium and thorium hydride complexes as multielectron reductants: a combined neutron diffraction and quantum chemical study.
abstract: The unusual uranium reaction system in which uranium(4+) and uranium(3+) hydrides interconvert by formal bimetallic reductive elimination and oxidative addition reactions, [(C(5)Me(5))(2)UH(2)](2) (1) ⇌ [(C(5)Me(5))(2)UH](2) (2) + H(2), was studied by employing multiconfigurational quantum chemical and density functional theory methods. 1 can act as a formal four-electron reductant, releasing H(2) gas as the byproduct of four H(2)/H(-) redox couples. The calculated structures for both reactants and products are in good agreement with the X-ray diffraction data on 2 and 1 and the neutron diffraction data on 1 obtained under H(2) pressure as part of this study. The interconversion of the uranium(4+) and uranium(3+) hydride species was calculated to be near thermoneutral (~-2 kcal/mol). Comparison with the unknown thorium analogue, [(C(5)Me(5))(2)ThH](2), shows that the thorium(4+) to thorium(3+) hydride interconversion reaction is endothermic by 26 kcal/mol.
authors.affiliation: Department of Chemistry, University of Minnesota and Supercomputing Institute, Minneapolis, Minnesota 55455, USA.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Grant
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Stewart
authors.forename: Robert
authors.initials: R
authors.lastname: Bau
authors.forename: Kevin A
authors.initials: KA
authors.lastname: Miller
authors.forename: Sax A
authors.initials: SA
authors.lastname: Mason
authors.forename: Matthias
authors.initials: M
authors.lastname: Gutmann
authors.forename: Garry J
authors.initials: GJ
authors.lastname: McIntyre
authors.forename: Laura
authors.initials: L
authors.lastname: Gagliardi
authors.forename: William J
authors.initials: WJ
authors.lastname: Evans