Polysulfonylamines, CXXVII - Hydrogen bonding in crystalline onium dimesylamides: A robust eight-membered ring synthon as a component in three-dimensional hydrogen bonding patterns

In order to study crystal packings and hydrogen bonding frameworks, low-tem perature X-ray structures were determined for three onium salts of general formula BH+(MeSO2)(2)N-, where BH+ is acetamidinium (1, monoclinic, space g roup P2(1)/c, Z = 4), guanidinium (2, monoclinic, P2(1)/c, Z = 4), or 4,6-d iamino-2-thioxo-2,3-dihydropyrimidinium (3, monoclinic P2(1)/n, Z = 4), In every case the ions create three-dimensional N-H ... N/O networks, in which all N-H donors of the cations and four (in 1) or five (2, 3) accepters of the anion are involved; non-conventional secondary bonds, e.g. C-H ... O/N, do not play an important role in the packings. For the isotypic structures 1 and 2, congruencies and dissimilarities of the hydrogen bonding patterns are discussed in detail. Despite the structural and chemical differences b etween the cations and the way in which they are attached to the anion, eac h of the three structures displays a robust eight-membered ring synthon [N- 2 = R-2(2)(8), antidromic] constructed via two-centre hydrogen bonds from a syn, syn-sequence H-N-C(sp(2))-N-H of the respective cation and a V-shaped O-S(sp(3))-N fragment of the anion. Although the networks in 2 and 3 conta in several N-H(... O)(2) three-centre interactions, the two-point connectiv ity of the synthon is distinctly preserved. The results indicate that the ( MeSO2)(2)N- ion may be utilized in crystal engineering as a dependable buil ding block.