Polysulfonylamines, CXXVI - Hydrogen bonding in crystalline onium dimesylamides: A robust eight-membered ring synthon in coexistence with a third hydrogen bonding motif - Cyclodimers, chains, supramolecular linkage isomers, and a quintuply interwoven three-dimensional C-H center dot center dot center dot O network

As an exercise in crystal engineering, low-temperature X-ray structures wer e determined for six rationally designed ionic solids of general formula BH +(MeSO2)(2)N-, where BH+ is 2-aminopyridinium (2, monoclinic, space group P 2(1)/c, Z = 4), 2-aminopyrimidinium (3, orthorhombic, Pbca. Z = 8), 2-amino thiazolium (4, orthorhombic, Pbcn, Z = 8), 2-amino-6-methyl-pyridinium (5, solvated with 0.5 H2O, monoclinic, C2/c, Z = 8), 2-amino-1,3,4-thiadiazoliu m (6, triclinic, P (1) over bar, Z = 2), or 2-amino-4,6-dimethylpyrimidiniu m (7, orthorhombic. Fdd2, Z = 16). The onium cations in question exhibit a trifunctional hydrogen-bond donor sequence H-N(H*)-C(sp(2))-N-H, which is c omplementary to an O-S(sp(3))-N fragment of the anion and simultaneously ex pected to form a third hydrogen bond via the exocyclic N-H* donor. Conseque ntly all the crystal packings contain cation-anion pairs assembled by an N- H ... N and an N-H ... O hydrogen bond. these substructures being mutually associated through an N-H*... O bond. Fbr the robust eight-membered ring sy nthon within the ion pairs [graph set N-2 = R-2(2)(8), antidromic], two sup ramolecular isomers were observed: In 2 and 3, N-H ... N originates from th e ring NH donor and N-H ... O from the exocyclic amino group, whereas in 4- 7 these connectivities are reversed. The third hydrogen bond, N-H*... O, le ads either to chains of ion pairs (generated by a 2(1) transformation in 2- 4 or by a glide plane in 5) or to cyclic dimers of ion pairs (C-i-symmetric in 6, C-2-symmetric in 7). The overall variety of motifs observed in a sma ll number of structures reflects the limits imposed on the prediction of hy drogen bonding patterns. Owing to the excess of potential accepters over tr aditional hydrogen-bond donors, several of the structures display prominent non-classical secondary bonding. Thus, the cyclodimeric units of 6 are ass ociated into strands through short antiparallel O ... S(cation) interaction s. In the hemihydrate 5, two independent C-H(cation)... O bonds generate a second antidromic R-2(2)(8) pattern, leading to sheets composed of N-H ... N/O connected catemers; the water molecules are alternately sandwiched betw een and O-H ... O bonded to the sheets to form bilayers, which are cross-li nked by a third C-H(cation)... O contact. The roof-shaped cyclodimers occur ring in 7 occupy the polar C-2 axes parallel to z and build up hollow C-ar- H ... O bonded tetrahedral lattices, in order to fill their targe empty cav ities, five translationally equivalent lattices mutually interpenetrate.