Molecular and Polymeric Uranyl and Thorium Complexes with Sulfonate-Containing Ligands

International audienceSix uranyl and one thorium(IV) cation complexes with ligands involving either only sulfonate or both sulfonate and carboxylate groups as complexing sites were obtained, mainly under hydrothermal conditions, and their crystal structures were determined. The uranyl ion complex with the 2-sulfobenzoate (2-SB2-) anion synthesized in the presence of pyridine, [pyH](4)[(UO2)(2)(2-SB)(2)O](2)center dot 4H(2)O (1), is a molecular, tetranuclear complex in which 2-SB2- is chelating through its two functional groups, while [Th(2-SB)(2)(H2O)(3)]center dot 2H(2)O (2) is a 1D polymer with monodentate sulfonate and bridging bidentate carboxylate groups. Complex [(UO2)(3)K(4-SB)O(OH)(3)(H2O)(1.5)]center dot 0.5H(2)O (3), with the 4-sulfobenzoate ligand, crystallizes as a 3D framework in which uranyl oxo/hydroxo 1D subunits are connected to one another by 4-SB2- and potassium cation bridges, the latter being involved in as much as five bonds with uranyl oxo groups (cation-cation bonds). Complex [UO2(5-SSH2)(H2O)(3)](2)center dot 2(5-SSH2)center dot 3H(2)O (4), with 5-sulfosalicylic acid (5-SSH3), is a dinuclear species in which the ligand is only coordinated through its bridging bidentate sulfonate group, an unusual occurrence. 5-Sulfosalicylic acid undergoes partial desulfonation and carboxylation under hydrothermal conditions, yielding the heterometallic, tetranuclear complex [UO2Ni(5-SHIPH)(4-HIPH2)(bipy)(2)(H2O)](2)center dot(4-HIPH3) (5), 5-sulfonato-2-hydroxyisophthalic acid (5-SHIPH4) and 4-hydroxyisophthalic acid (4-HIPH3) being generated in situ. The all-sulfonate ligand 1,2-ethanedisulfonate (EDS2-) acts as a divergent linker in both [UO2(EDS)(H2O)(3)] (6) and [(UO2)(2)(EDS)(OH)(2)(phen)(2)]center dot 4H(2)O (7). 1D polymers are formed in both cases, the doubly monodentate EDS2- ligand bridging isolated uranyl ions in 6 or hydroxo-bridged uranyl dimers in 7. Sulfonate coordination to the 5f cation is present in all these complexes but 5, even in the absence of synergistic effects exerted by the stronger carboxylate ligating groups, and the variety of structures obtained in this as well as in previous work demonstrates that, together with the more investigated phosphonates, sulfonates are anions of great potential for the synthesis of actinide-organic coordination polymers and frameworks