Dilithium 1,2,5-thia­diazo­lidine-3,4-dione 1,1-dioxide dihydrate

The title compound, poly[μ-aqua-aqua-μ₆-(1,1-dioxo-1λ⁶,2,5-thia­diazo­lidine-3,4-diolato)-dilithium], [Li₂(C₂N₂O₄S)(H₂O)₂]_n or (H₂O)₂:Li₂TDD, forms an infinite three-dimensional structure containing five-coordinate (Li/5) and six-coordinate (Li/6) Li⁺ cations. Li/5 is coordinated by three water mol­ecules, one carbonyl O atom and one sulfuryl O atom while Li/6 is coordinated by one water mol­ecule, three carbonyl O atoms, and two sulfuryl O atoms. Each water mol­ecule bridges two Li⁺ cations, while also hydrogen bonding to either one endocyclic N atom and one sulfuryl O atom or two endocyclic N atoms. While the endocyclic N atoms in the anion do not coordinate the Li⁺ cations, the carbonyl and sulfuryl groups each coordinate three Li⁺ cations, which gives rise to the infinite three-dimensional structure.