The Versatile Structural World of Methanedi- and Trisulfonic Acid and Their Salts.

The syntheses and structural elucidations of 16 novel compounds, derived from methane(poly-)sulfonic acids are presented. The anhydrous acids, that is, methanedisulfonic acid (MDSA-(H2C(SO3H)2, 1) and methanetrisulfonic acid (MTSA), the latter as two polymorphic structures (HC(SO3H)3-I (P3c1, 2) and HC(SO3H)3-II (P21/n, 3)) have been crystallized and structurally elucidated. Methanedisulfonic acid was subsequently used to prepare four group I methanedisulfonates (AM2[(H2C(SO3)2], AM = Li (6), K (7)·H2O, Rb (8) and Cs (10)) as well as the strontium dihydrate Sr[H2C(SO3)2](H2O)2 (9) and the ternary salt BaK2[(H2C(SO3)2]2 (11). The known trisulfonate K3[HC(SO3)3](H2O) was used for the preparation of the oxonium salt [H3O]3[HC(SO3)3] (4), which was isolated as a new polymorph (R3c). Subsequent neutralization led to isolation of the compounds AM3[HC(SO3)3] (AM = Li (12)·(H2O)4, K (13), Rb (14)·H2O, as well as the two ternary salts Rb3Ag3[HC(SO3)3]2 (15) and Rb5Ag[HC(SO3)3]2(H2O)2 (16). For a structural comparison between a mono-, di-, and trisulfonate, we also prepared the still elusive rubidium methanesulfonate, which crystallizes as the hydrate Rb[H3C(SO3)](H2O) (5). Different synthetic approaches, as well as an in-depth structural analysis of all compounds, are presented. Furthermore, compound 8 and the oxonium salt of compound 1 were investigated concerning their thermal decomposition.