(S,S)-N,N′-Bis(1-carboxy-2-methylpropyl)ethylenediammonium dihalide cyclopentanol tetrasolvate (halide = bromide/chloride ≃ 1:12)

In the crystal structure of the title compound, C12H26N2O4 2+·2(Br0.085Cl0.915)−·4C5H9OH, the complete cation is generated by crystallographic twofold symmetry. Contamination of the chloride counter-anion with bromide occured during the preparation, due to the use of 1,2-dibromoethane. One of the solvent molecules is disordered, with occupancies 0.53 (3):0.47 (3). The crystal packing is stabilized by an infinite two dimensional ⋯X⋯H—N—H⋯X⋯ hydrogen-bonding network (X: Br−/Cl− ≃ 1:12). In addition, O—H⋯X and O—H⋯O hydrogen bonds involving solvent molecules are observed.

Crude (S,S)-ethylenediammonium-N,N'-di-2-(3-methyl)-butanoic acid dihalide, [(H 4 eddv)X 2 ], obtained from the reaction of L-valine and 1,2-dibromethane (Schoenberg et al.,1968), was used for the synthesis of dicyclopentyl ester. The title compound is isolated from the mother liquor as a mixture of Cl and Br salts. The structure consists of several species: one dic-  et al., 2004, 2007). All of the mentioned species are stabilizing the structure by intramolecular and intermolecular H-bonds (Table 1). The solvent molecules are involved in hydrogen bonding, through O4-H4O···O3 atoms (Fig. 2). Furthermore, the H3O atom bonded to O3 is participating in hydrogen bonding with X atom (X: Br -/Cl -≈ 1:12), which is on the other side interacting via hydrogen bond with the H1N-N1 moiety. The cyclopentyl rings are in envelope conformations.

Refinement
The H atoms connected to the nitrogen and oxygen atoms were found in difference maps and yielded reasonable bond  Fig. 1. ORTEP representation of [(H 4 eddv)X 2 ] . 4C 5 H 9 OH. The structure contains a 1:12 Br/ Cl (X) disorder. The figure displays the Cl-part of this disorder (Cl1). Displacement ellipsoids are plotted at the 50% probability level and H atoms are shown as small spheres of arbitrary radii.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (