Polysulfonylamines, CLXX [1].: Hydrogen bonding in crystalline onium dimesylamides:: Three structures involving NH2-substituted 1,3,5-triazinium cations (including melaminium)

In order to study hydrogen bonding networks and packing arrangements, preparations and low-temperature X-ray structures are reported for three ionic solids of general formula BH+ (MeSO2)(2)N-, where BH+ is 2,6-diamino-4-phenyl-1,3,5-triazin-1-ium (compound 1, tetragonal, space group P42(1)c, Z = 8), 2,4,6-triamino-1,3,5-triazinium or melaminium (2, monoclinic, P2(1)/c, Z = 4), and 2,4-diamino-6-methyl-1,3,5-triazin-1-ium (3, triclinic, Pi, Z = 2). The asymmetric units consist of cation-anion pairs that display in I a [DDD:AAA] three-point hydrogen bond pattern formed by two lateral N-(HO)-O-... bonds and a central N+-(HN)-N-... interaction, in 2 a related pattern, in which the substantial lateral offset of the ions causes the two-centre H bonds to split up into three-centre bonds, and in 3 a [DD:AA] two-point pattern formed by an N-(HN)-N-... and an N+-(HO)-O-... interaction. All NH donors that are not involved in the ion pairs use sulfonyl oxygen atoms and/or non-protonated nitrogen ring-atoms as acceptors to form, in I and 3, discrete cation-anion strands, and in 2 similar strands associated into a three-dimensional network via one independent N-(HO)-O-... bond. The packing topologies of the strands may be viewed as supramolecular analogues to molecular arrangements occurring in crystalline polyaromatic hydrocarbons, viz. the sandwich-herringbone pattern in 1 (sustained by pi(...)pi stacking of the triazine rings within the sandwiches and a phenyl-phenyl C-H(...)pi interaction between orthogonal sandwiches), the flattened or gamma-type herringbone pattern in 2 (sustained by the unique N-(HO)-O-... interaction of orthogonal strands), and the pseudo-graphitic beta-pattern in 3. In each packing, weak C-H(...)A hydrogen bonds (A = O, N) originate from the activated methyl groups of the anions and act as structure-supporting links between the cation-anion strands.