Hydration and Hydrolysis of Thorium(IV) in Aqueous Solution and the Structures of Two Crystalline Thorium(IV) Hydrates
2009 (English)In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 48, no 24, 11712-11723 p.Article in journal (Refereed) Published
Solid octaaqua(kappa O-2-perchlorato)thorium(IV) perchlorate hydrate, [Th(H2O)(8)(ClO4)](ClO4)(3)center dot H2O, 1, and aqua-oxonium hexaaquatris(kappa O-trifluoromethanesulfonato)thorium(IV) trisaquahexakis(kappa O-trifluoromethanesulfonato)-thorinate(IV), H5O2[Th(H2O)(6)(OSO2CF3)(3)][Th(H2O)(3)(OSO2CF3)(6)], 2, were crystallized from concentrated perchloric and trifluoromethanesulfonic acid solutions, respectively. 1 adopts a severely distorted tricapped trigonal prismatic configuration with an additional oxygen from the perchlorate ion at a longer distance. 2 consists of individual hexaaquatris(kappa O-trifluoromethanesulfonato)thorium(IV) and trisaquahexakis(kappa O-trifluoromethanesulfonato)thorinate(IV) ions and an aquaoxonium ion bridging these two ions through hydrogen bonding. The hydrated thorium(IV) ion is nine-coordinated in aqueous solution as determined by extended X-ray absorption fine structure (EXAFS) and large angle X-ray scattering (LAXS). The LAXS studies also showed a second hydration sphere of about 18 water molecules, and traces of a 3rd hydration sphere. Structural studies in aqueous solution of the hydrolysis products of thorium(IV) have identified three different types of hydrolysis species: a mu O-2-hydroxo dimer, [Th-2(OH)(2)(H2O)(12)](6+), a mu O-2-hydroxo tetramer, [Th-4(OH)(8)(H2O)(16)](8+), and a mu O-3-oxo hexamer, [Th6O8(H2O)(n)](8+). Detailed structures of these three hydrolysis species are given A compilation of reported solid state structures of actinoid(IV) compounds with oxygen donor ligands show a strong correlation between the An-O bond distance and the coordination number. The earlier reported U-O bond distance in the hydrated uranium(IV) ion in aqueous solution, confirmed in this study, is related to nine-coordination. The hydrated tri- and tetravalent actinoid ions in aqueous solution all seem to be nine-coordinated The trivalent ions show a significant difference in bond distance to prismatic and capping water molecules in assumed tricapped trigonal prismatic configuration, while the tetravalent ions seem to form more regular structures, probably because of higher polarization.
Place, publisher, year, edition, pages
2009. Vol. 48, no 24, 11712-11723 p.
ray-absorption spectroscopy, compton-scattering factors, nitrate solutions, free atoms, aqua ion, complexes, spectra; exafs, coordination, perchlorate
IdentifiersURN: urn:nbn:se:su:diva-59400DOI: 10.1021/ic901763sISI: 000272556700035OAI: oai:DiVA.org:su-59400DiVA: diva2:427664
authorCount :42011-06-282011-06-272011-06-28Bibliographically approved