Adamantane-1-ammonium benzoate

In the title molecular salt, C10H15NH3 +·C7H5O2 −, both carboxyl O atoms act as acceptors for strong N—H⋯O intermolecular hydrogen-bond interactions with the ammonium group in the cation, generating infinite chains along the b axis. A weak C—H⋯π interaction is also present.

In the title molecular salt, C 10 H 15 NH 3 + ÁC 7 H 5 O 2 À , both carboxyl O atoms act as acceptors for strong N-HÁ Á ÁO intermolecular hydrogen-bond interactions with the ammonium group in the cation, generating infinite chains along the b axis. A weak C-HÁ Á Á interaction is also present.

Comment
Owing to its highly symmetrical and stable structure, adamantane and its derivatives have generated much interest in the past and continue to be actively studied as evidenced by the large number of compounds containing amantadine that have been synthesized (Tukada & Mochizuki, 2003;Zhao et al., 2003;He & Wen, 2006). Here we report the synthesis and crystal structure of the title compound,(I), C 10 H 15 NH 3 + . C 7 H 5 O 2 -, a salt obtained from the reaction of adamantane-1-ammonium hydrochloride and sodium benzoate (Fig. 1).
The adamantane-1-ammonium cation contains four 6-membered rings in a cage-like structure each in a slightly distorted boat conformation and with a protonated N atom at the 1-position. Puckering parameters (Cremer & Pople, 1975 Table 1). In addition, weak π-ring C16-H16A···Cg1 interactions exist which contribute to crystal stability (Cg1 is the center of gravity of ring 1).

Experimental
A mixture of adamantane-1-ammonium hydrochloride (10 mmol), sodiumbenzoate (10 mmol) and methanol (50 ml) was stirred in a beaker. There were many solid powders produced and the solution was filtered. Colorless single crystals of the title compound suitable for X-ray analysis were obtained by slow evaporation of the solvents over a period of 20 h.

Refinement
Positional parameters of all the H atoms were calculated geometrically (aromatic C-H = 0.93 A°, aliphatic C-H = 0.97 A°) & N-H = 0.89Å) and were allowed to ride on the C,N atoms to which they are bonded, with U iso (H) = 1.2-1.5U eq (C,N). Fig. 1. The molecular structure of the title compound, with the atomic numbering scheme and displacement ellipsoids drawn at the 30% probability level. All H atoms except those on the N atom have been omitted for clarity.

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 > σ(F 2 ) is used only for calculating Rfactors(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.