Hydrothermal Synthesis of Disulfide-Containing Uranyl Compounds: In Situ Ligand Synthesis versus Direct Assembly

Three disulfide-containing uranyl compounds, [UO2(C7H4O2S)3]·H2O (1), [UO2(C7H4O2S)2(C7H5O2S)] (2), and [UO2(C7H4O2S)4] (3) have been hydrothermally synthesized. Both in situ disulfide bond formation from 3- and 4-mercaptobenzoic acid (C7H5O2S, MBA) to yield 3,3′- and 4,4′-dithiobisbenzoic acid (C14H8O4S2, DTBA) and direct assembly with the presynthesized dimeric ligands have been explored. While the starting materials 4-MBA and 4,4′-DTBA both yield 2 via in situ ligand synthesis and direct assembly, respectively, we observe the formation of 1 from the starting material 3-MBA via in situ ligand synthesis and of 3 from the direct assembly of the uranyl cation with 3,3′-DTBA. Concurrently with the synthesis of 1 and 2, we have observed the in situ formation of the crystalline dimeric organic species, 3,3′-DTBA, [(C7H5O2S)2] (4) and 4,4′-DTBA, [(C7H5O2S)2] (5). Herein we report the synthesis and crystallographic characterization of 1−5, as well as observations regarding the utility of product formation via direct assembly and in situ ligand synthesis.