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—(H 2 C(SO 3 H) 2 , 1 ) and methanetrisulfonic acid (MTSA), the latter as two polymorphic structures (HC(SO 3 H) 3 ‐I ( P 3 c 1, 2 ) and HC(SO 3 H) 3 ‐II ( P 2 1 / n , 3 )) have been crystallized and structurally elucidated. Methanedisulfonic acid was subsequently used to prepare four group I methanedisulfonates (AM 2 [(H 2 C(SO 3 ) 2 ], AM = Li ( 6) , K ( 7 )·H 2 O, Rb ( 8 ) and Cs ( 10 )) as well as the strontium dihydrate Sr[H 2 C(SO 3 ) 2 ](H 2 O) 2 ( 9 ) and the ternary salt BaK 2 [(H 2 C(SO 3 ) 2 ] 2 ( 11 ). The known trisulfonate K 3 [HC(SO 3 ) 3 ](H 2 O) was used for the preparation of the oxonium salt [H 3 O] 3 [HC(SO 3 ) 3 ] ( 4 ), which was isolated as a new polymorph ( R 3 c ). Subsequent neutralization led to isolation of the compounds AM 3 [HC(SO 3 ) 3 ] (AM = Li ( 12 )·(H 2 O) 4 , K ( 13 ), Rb ( 14 )·H 2 O, as well as the two ternary salts Rb 3 Ag 3 [HC(SO 3 ) 3 ] 2 ( 15 ) and Rb 5 Ag[HC(SO 3 ) 3 ] 2 (H 2 O) 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[H 3 C(SO 3 )](H 2 O) ( 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.