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

The title compound, poly[μ-aqua-aqua-μ(6)-(1,1-dioxo-1λ(6),2,5-thia­diazo­lidine-3,4-diolato)-dilithium], [Li(2)(C(2)N(2)O(4)S)(H(2)O)(2)](n) or (H(2)O)(2):Li(2)TDD, 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.