Two Light‐Metal Dihydrogenisocyanurate Hydrates Linked by Diagonal Relationship: Syntheses, Crystal Structures, and Vibrational Spectra of Li[H2N3C3O3]·1.75 H2O and Mg[H2N3C3O3]2·8 H2O

Abstract

Single‐crystalline materials of Li[H2N3C3O3]·1.75 H2O and Mg[H2N3C3O3]2·8 H2O were obtained by dissolving stoichiometric amounts of the respective carbonates with cyanuric acid in boiling water followed by gentle evaporation of excess water after cooling to room temperature. Even though both of these compounds crystallize in the triclinic space group P1 according to X‐ray structure analyses of their colorless and transparent single crystals, they adopt two new different structure types. Li[H2N3C3O3]·1.75 H2O exhibits the unit‐cell parameters a = 884.71(6) pm, b = 905.12(7) pm, c = 964.38(7) pm, α = 67.847(2)°, β = 62.904(2)° and γ = 68.565(2)° (Z = 4), whereas the lattice parameters for Mg[H2N3C3O3]2·8 H2O are a = 691.95(5) pm, b = 1055.06(8) pm, c = 1183.87(9) pm, α = 85.652(2)°, β = 83.439(2)° and γ = 79.814(2)° (Z = 2). In both cases, the singly deprotonated isocyanuric acid forms monovalent anions consisting of cyclic [H2N3C3O3]– units, which are arranged in ribbons typical for most hitherto known monobasic isocyanurate hydrates. The structures are governed by the oxophilic strength of the respective cation which means that they fulfil their oxophilic coordination requirements either solely with water molecules ([Mg(OH2)6]2+ for Mg2+) or with crystal water and one or two direct coordinative contacts to carbonyl oxygen atoms (O(cy)) of [H2N3C3O3]– anions ([(Li(OH2)2–3(O(cy)1–2]+ for Li+). In both structures occur dominant hydrogen bonds N–H···O within the anionic [H2N3C3O3]– ribbons as well as hydrogen bonds O–H···O between these ribbons and the hydrated Li+ and Mg2+ cations.