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

Three disulfide-containing uranyl compounds, [UO 2 (C 7 H 4 O 2 S) 3 ]·H 2 O ( 1 ), [UO 2 (C 7 H 4 O 2 S) 2 (C 7 H 5 O 2 S)] ( 2 ), and [UO 2 (C 7 H 4 O 2 S) 4 ] ( 3 ) have been hydrothermally synthesized. Both in situ disulfide bond formation from 3- and 4-mercaptobenzoic acid (C 7 H 5 O 2 S, MBA) to yield 3,3′- and 4,4′-dithiobisbenzoic acid (C 14 H 8 O 4 S 2, 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, [(C 7 H 5 O 2 S) 2 ] ( 4 ) and 4,4′-DTBA, [(C 7 H 5 O 2 S) 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.