Probing the Influence of Acidity and Temperature to Th(IV) on Hydrolysis, Nucleation, and Structural Topology

• Published in: Inorganic chemistry Vol. 56; no. 22; pp. 14198 - 14205
• Main Authors: Lin, Jian, Qie, Meiying, Zhang, Linjuan, Wang, Xiaomei, Lin, Yuejian, Liu, Wei, Bao, Hongliang, Wang, Jianqiang
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 20.11.2017
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.7b02335

Systematic control of the molar ratio between thorium hydroxides and selenic acid and their reaction temperature under hydrothermal conditions results in four novel thorium-based selenate complexes, namely, [Th8O4(OH)8­(SeO4)6(H2O)16]·(SeO4)2·13H2O (Th-1), [Th8O4(OH)8­(SeO4)8(H2O)13]·7H2O (Th-2), Th­(OH)2­(SeO4)­H2O (Th-3), and Th3(SeO4)6(H2O)6·2.5H2O (Th-4), as well as the thorium mixed selenite selenate compound Th­(SeO3)­(SeO4) (Th-5). Smaller [H2SeO4]/[Th­(IV)] ratio or lower temperature give rise to the formation of octameric [Th8(μ3-O)4­(μ2-OH)8]16+ cores in Th-1/Th-2 and infinite [Th­(μ2-OH)2H2O]2+ chains in Th-3, respectively. Increasing the [H2SeO4]/[Th­(IV)] ratio or elevating the temperature generates a microporous (11.3 Å voids) open-framework Th-4, a monomeric thorium species without oxo/hydroxyl ligands, and a three-dimensional thorium structure Th-5. Formation of these compounds suggests that variables including acidity and temperature play a critical role in the hydrolysis and oligomerization of ThIV ions. Increasing acidity limits the deprotonation of water molecules and formation of nucleophilic hydroxo/oxo-aquo Th species, and high temperature appears to suppress the olation/oxolation hydrolysis reactions, which in both ways limit the formation of the thorium oligomers.