Polymeric structures in the metal complexes of 5-sulfosalicylic acid: The rubidium(I), caesium(I) and lead(II) analogues

The complexes of 3-carboxy-4-hydroxybenzenesulfonic acid (5-sulfosalicylic acid, H₃SSA) with rubidium(I), caesium(I) and lead(II) have been synthesized and characterized using single-crystal X-ray methods at 130 K. The rubidium(I) complex 1, [Rb₃(H₂SSA)(HSSA)(H₂O)₄]_n, is an unstable hydrate variant of a previously described complex [Rb(H₂SSA)(H₂O)]_n, and comprises three independent and different seven-coordinate metal polyhedra interlinked through oxygen donors of the sulfonate, carboxylate and phenolate groups of the 5-sulfosalicylate ligands (one of which is dianionic, the other monoanionic), and one bridging water, giving a three-dimensional hydrogen-bonded framework polymer structure. The anhydrous caesium(I) complex 2 [Cs(H₂SSA)]_n, which has been previously described in a room-temperature determination, has a three-dimensional framework polymer structure based on an irregular Cs–O₉ repeating unit. Complex 3 with lead(II), [Pb(H₂SSA)₂(H₂O)]_n, forms helical step-polymer ribbon substructures having an irregular Pb–O₇ coordination centre comprising a single monodentate water and six sulfonate-O donors bridging three separate metals. The carboxylic acid and phenol substituent groups of the 5-sulfosalicylate ligand link the ribbons peripherally through hydrogen bonds, giving a three-dimensional layered framework polymer structure.