Butane-1,4-diammonium bis(perchlorate)

The butane-1,4-diammonium cation of the title compound, C4H14N2 2+·2ClO4 −, lies on a special position of site symmetry 2/m, whereas the perchlorate anion is located on a crystallographic mirror plane. An intricate three-dimensional hydrogen-bonding network exists in the crystal structure with each H atom of the ammonium group exhibiting bifurcated interactions to the perchlorate anion. Complex hydrogen-bonded ring and chain motifs are also evident, in particular a 50-membered ring with graph-set notation R 10 10(50) is identified.


Comment
The crystal structure of the title compound (I) adds to our current ongoing studies of long-chained diammonium mineral acid salts. Colourless rectangular crystals of butane-1,4-diammonium diperchlorate were synthesized and formed part of our structural chemistry study of the inorganic mineral acid salts of butane-1,4-diamine.
The butane-1,4-diammonium cation lies over an inversion centre and a twofold rotation axis. It also straddles a crystallographic mirror plane. The asymmetric unit contains one-half of a perchlorate anion and one-half of the butane-1,4-diammonium cation. The hydrocarbon chain is also fully extended and is of necessity completely planar as it lies in the crystallographic mirror plane. The molecular structure of (I) is shown in Figure 1. -organic layering effect that is a common feature of these long-chained diammonium salts. An extensive three-dimensional hydrogen-bonding network is formed.
A close-up view of the hydrogen bonding interactions can be viewed in Figure 3 where very clear evidence of bifurcated interactions can be seen on each hydrogen atom of both ammonium groups. The hydrogen bond distances and angles for (I) can be found in Table 2.
Since the hydrogen bonding network is extremely intricate and complex, we focus on one particularly interesting hydrogen-bonding ring motif in the structure. Figure 4 shows a view of five diammonium cations and five perchlorate anions (viewed down the a axis) that are hydrogen bonded together to form a large, level 2, 50-membered ring motif with graph set notation R 10 10 (50). Numerous other ring and chain motifs were identified with Mercury (Macrae et al.), but since the one in Figure 4 is the highest level motif obtainable in the structure, the other motifs of lower level are not depicted here.

Experimental
The title compound was prepared by adding butane-1,4-diamine (0.50 g, 5.67 mmol) to 30% perchloric acid (HClO 4 , 2 ml, 9.138 mmol, Merck) in a sample vial. The mixture was then refluxed at 363 K for 2 h. The solution was cooled at 2 K h -1 to room temperature. Colourless crystals of butane-1,4-diammonium diperchlorate were collected and a suitable single-crystal was selected for the X-ray diffraction study.

Refinement
Hydrogen atoms could be identified from the difference Fourier map but once these atoms were refined, their distances from the parent atoms were found to be significantly shorter than the ideal distances for C-H and N-H respectively.
The H-atoms were therefore geometrically positioned and refined in the riding-model approximation, with C-H = 0.97 Å, supplementary materials sup-2 N-H = 0.89 Å, and U iso (H) = 1.2Ueq(C) or 1.5Ueq(N). The highest peak in the final difference map is 0.69Å from O2 and the deepest hole is 0.69Å from Cl1. Fig. 1. : Molecular structure of the title compound, with atomic numbering scheme and displacement ellipsoids drawn at the 50% probability level.