Polysulfonylamine, CXVII Wasserstoffbrücken in kristallinen Onium-dimesylamiden: Sechs systematisch variierte sek.-Ammonium-dimesylamide mit sechs verschiedenen null-, ein-oder zweidimensionalen Wasserstoffbrückenmustern/ Polysulfonylamines, CXVII Hydrogen Bonding in Crystalline Onium Dimesylamides: Six Systematically Varied sec. - Ammonium Dimesylamides Exhibiting Six Different Zero-, One-, or Two-Dimensional Hydrogen Bonding Patterns

In order to examine packing preferences and hydrogen bond patterns in secondary ammonium salts, low-temperature X-ray analyses were conducted for six compounds of general formula R₂NH₂⁺MeSO₂)₂ N^-, where R₂NH₂⁺ = Me₂NH₂⁺ (1, triclinic, space group P1̄̄), MeEtNH₂⁺,(2, monoclinic, P2₁/c), Et₂NH₂⁺ (3. triclinic, P1), pyrrolidinium (4, triclinic, P1), piperidinium (5, monoclinic, C2/c) or morpholinium (6, monoclinic, P2_1/c). Throughout the series, the constant anion retains a rigid conformation approximating to C₂ symmetry and thus provides a geometrically reliable set of five potential hydrogen bond acceptors. Nevertheless, the six compounds exhibit a variety of unpredictable packing patterns, showing that, in unfavourable cases, the steric demands of molecular fragments not involved in hydrogen bonding can substantially alter the structure of a family of ionic crystals. In the present structures, the NH₂⁺ donor groups form hydrogen bonds N⁺-H···N^-/O to two (3-6) or three (1,2) adjacent anions. The occurrence of various two-, three- and four-centre hydrogen bonds leads to six different patterns, resulting in cation-anion layers (1, 2), discrete formula unit dimers (3, 4) or cation-anion chains (5, 6); in the morpholinium salt 6, these chains are associated into layers by a weak N⁺ - H ··· O(cation) interaction. In each of the crystal packings, short C-H···O contacts with H···O ≤ 270 pm and C-H ···O ≥ 130° are observed.