Polysulfonylamine, CLIII [1]. Schwache Wasserstoffbrücken mit aktivierten Methyldonoren: Kristallstrukturen von Cholinium-, Betainium- und Dimethyl[2-(dimethylamino)ethyl]ammonium-dimesylamid Polysulfonylamines, CLIII [1]. Weak Hydrogen Bonding with Activated Methyl Donors: Crystal Structures of Cholinium, Betainium and Dimethyl[2-(dimethylamino)ethyl]ammonium-dimesylamide

In order to study weak hydrogen bonds originating from inductively activated C(sp³)-H donor groups, low-temperature X-ray structures are reported for three onium salts of general formula BH⁺(MeSO₂)₂N-, where BH⁺ is Me₃N⁺CH₂CH₂OH (1; orthorhombic, space group P2₁2₁2₁, Z′ = 1), Me₃N⁺CH₂C(O)OH (2; orthorhombic, P2₁2₁2₁, Z′ = 1), or Me₂HN⁺CH₂CH₂NMe₂ (3; monoclinic, P2₁/c, Z′ = 1). The asymmetric units consist of cationanion pairs assembled by an O-H···O=S hydrogen bond in 1, an O-H···N- bond in 2, and an N⁺-H ··· N^- bond in 3. The packings display a plethora of short interionic C(sp³)-H···O/N contacts that are geometrically consistent with weak hydrogen bonding; those taken into consideration have normalized parameters d(H ··· O) ≤ 269 pm, d(H···N) ≤ 257 pm and θ(C-H···O/N) ≥ 127°. The roles of the weak hydrogen bonds are as follows: In structures 1 and 3, the anions are associated into corrugated layers, which intercalate catemers of cations (1) or stacks of discrete cations (3), whereas structure 2 involves cation catemers surrounded by four anion catemers and vice versa; moreover, all cations are linked to adjacent anions by several weak hydrogen bonds (and to one anion in particular by the strong H bond). Among the cation-anion interactions, the N⁺(CH₂-H···)₃O tripod pattern arising in 1 and 2 is of special interest.