1,3-Diammonio-1,2,3-trideoxy-cis-inositol sulfate

In the crystal structure of the title compound, C6H16N2O3 2+·SO4 2−, each cation forms three O—H⋯O and five N—H⋯O hydrogen bonds to six neighbouring sulfate anions. In addition, interlinking of the cations by N—H⋯O interactions is also observed. The cyclohexane ring adopts a chair conformation with two axial hydroxy groups. Although the separation of 2.928 Å is almost ideal for a hydrogen bond, intramolecular hydrogen bonding between these two hydroxy groups is not observed.

In the crystal structure of the title compound, C 6 H 16 N 2 O 3 2+ Á-SO 4 2À , each cation forms three O-HÁ Á ÁO and five N-HÁ Á ÁO hydrogen bonds to six neighbouring sulfate anions. In addition, interlinking of the cations by N-HÁ Á ÁO interactions is also observed. The cyclohexane ring adopts a chair conformation with two axial hydroxy groups. Although the separation of 2.928 Å is almost ideal for a hydrogen bond, intramolecular hydrogen bonding between these two hydroxy groups is not observed.

1,3-Diammonio-1,2,3-trideoxy-cis-inositol sulfate Christian Neis, Günter J. Merten and Kaspar Hegetschweiler Comment
Due to the versatile metal-and hydrogen-binding properties, 1,3-diamino-1,2,3-trideoxy-cis-inositol has been found to be a promising building block for the construction of polynuclear metal complexes and extended hydrogen bonded networks . The crystal structure of a corresponding hydrochloride C 6 H 14 N 2 O 3 . 2HCl has recently been reported . Similar to this chloride salt, the title compound contains 1,3-diammonio-1,2,3-trideoxy-cis-inositol dications with the cyclohexane ring adopting an almost ideal chair conformation (puckering parameters: Q = 0.59 Å, θ = 178.3 °, φ = 89.0 °). In both salts, the cation has the same form with the two ammonium groups and one of the hydroxy groups in equatorial and the remaining two hydroxy groups in axial position. In the title compound, each cation is hydrogen-bonded to six sulfate counter ions by O-H···O and N-H···O interactions, one of the latter is bifurcated. These cation···anion interactions constitute an extended three-dimensional network. Direct cation···cation hydrogen bonding is also observed: One of the ammonium groups of each cation donates a hydrogen atom to the equatorial hydroxy group of a neighbouring cation and another hydrogen atom to the axial hydroxy group of an additional neighbour. Each cation is thus connected to a total of four neighbouring cations and these interactions generate double chains, which are oriented parallel to the crystallographic b axis. As already observed for the chloride salt, all O-H and N-H groups act as hydrogen donors, however, one of the axial hydroxy groups does not accept any hydrogen atom. We explain these observations by the well established stronger steric encumbrance of axial substituents. It is again worthy to note that the non-accepting axial hydroxy group does not form an intramolecular O-H···O hydrogen bond, even though the O···O separation of 2.928 Å between the two axial oxygen atoms corresponds almost ideally to the value required for such an interaction. For corresponding structures with three axial hydroxy or amino groups in a syn-1,3,5-triaxial arrangement, it appears, however, that the formation of such intramolecular hydrogen bonds is often a prerequisite for a stable cyclohexane chair (Gencheva et al., 2000;Kramer et al., 1998;Kuppert et al., 2006). The non-observance of such a hydrogen bond in the title compound further supports the conclusion that this type of interactions would be of minor importance in molecules having only two hydroxy groups in a 1,3-syn-axial arrangement.

Experimental
The title compound has been obtained following the protocol given by Merten et al. (2012). 1 H-NMR and 13 C-NMR properties are identical with the chloride salt . Single crystals were grown from an aqueous solution (pH 2) by slow evaporation at 298 K.

Refinement
All non-hydrogen atoms were refined using anisotropic displacement parameters. Hydrogen atoms were treated as

Figure 1
Molecular structure of the title compound with numbering scheme and displacement ellipsoids drawn at the 50% probability level.

Figure 2
The double chain structure which is formed by hydrogen bonding between dication entities (ball and stick model).

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.