Synthesis and Characterization of Thorium(IV) Sulfates

Three Th(IV) sulfates, two new and one previously reported, have been synthesized from aqueous solution. In all of the compounds, the sulfate anions coordinate the Th4+ metal center(s) in a monodentate manner with Th–S distances of 3.7–3.8 Å. Th(SO4)2(H2O)7·2(H2O) (1; P21/m, a = 7.224(1) Å, b = 12.151(1) Å, c = 7.989(1) Å, ss =98.289(2)°) and Th4(SO4)7(H2O)7(OH)2·H2O (2; Pnma, a = 18.139(2) Å, b = 11.173(1) Å, c = 14.391(2) Å) each contain 9-coordinate monomeric (1,2) and dimeric (2) Th(IV) cations in monocapped square antiprism geometry. Alternatively, Th(OH)2SO4 (3; Pnma, a = 11.684(1) Å, b = 6.047(1) Å, c = 7.047(1) Å) is built from chains of hydroxo-bridged, 8-coordinate Th4+ centers. Whereas 1 adopts a molecular structure, 2 and 3 both exhibit 3D architectures. Differences in the dimensionality and the topology of 1–3 are manifested in the local coordination environment about the Th(IV) centers, the formation of oligomeric Th4+ species, and the extended connectivity of the sulfate ligands. Herein, we report the syntheses and characterization of 1–3 as well as the atomic correlations of 1 in solution, as determined by high-energy X-ray scattering (HEXS).