Synthesis and crystal structure of 3-(adamantan-1-yl)-4-(2-bromo-4-fluorophenyl)-1H-1,2,4-triazole-5(4H)-thione

The crystal structure of this novel adamantan-based compound is built up by organic chains formed and stabilized via C—H⋯π, N—H⋯S and C—H⋯S interactions.


Hirshfeld surface analysis
In order to investigate the intermolecular interactions in the structure of I in a visual manner, a Hirshfeld surface analysis was performed using the program Crystal Explorer 17.5 (Spackman et al. 2002;Turner et al., 2017). Fig. 3 shows the HS surfaces mapped over d norm , shape-index and curvedness (Fig. 3). In the HS plotted over d norm , white areas on the surface indicate contacts with distances equal to the sum of van der Waals radii, and the red and blue colours indicate distances shorter (in close contact) or longer (distant contact) than the van der Waals radii, respectively. Two red spots are present in close proximity to the S and N-H atoms involved in hydrogen bonding. As expected, the absence of red and blue triangles on the shape-index surface and the small, flat segments delineated by the blue line in the surface mapped over curvedness indicate the absence ofstacking inter-    Table 1 Hydrogen-bond geometry (Å , ).

Figure 1
The molecular structure of the title compound with atom labels, showing displacement ellipsoids at the 50% probability level.
actions in the crystal structure, while the red regions over the shape-index surface are due to the presence of C-HÁ Á Á interactions.

Synthesis and crystallization
All chemicals and solvents were used as purchased without further purification. The melting point was determined using an electrothermal digital melting-point apparatus and uncorrected. The NMR spectra were recorded at room temperature in DMSO-d 6 solution on a Bruker Ascend 700 NMR spectrometer. The title compound I was synthesized starting with adamantane-1-carbohydrazide A (El-Emam & Ibrahim, 1991) via the reaction with 2-bromo-4-fluorophenyl isothiocyanate B to yield the corresponding 4-(1-adamantylcarbonyl)-1-(2bromo-4-fluorophenyl)-2-thiosemicarbazide C, which was then cyclized to the title compound I by heating in aqueous sodium hydroxide as outlined in Fig. 6.
2-Bromo-4-fluorophenyl isothiocyanate (2.32 g, 0.01 mol) was added to a solution of adamantane-1-carbohydrazide (1.94 g, 0.01 mol), in ethanol (10 mL   Relative contribution of the various intermolecular interactions in compound I. mixture was heated under reflux for 4 h, then filtered hot. On cooling, the mixture was acidified with hydrochloric acid (pH 1-2) and the precipitated crude product was filtered, washed with water, dried and crystallized from an aqueous medium to yield 3.06 g (75%) of the title compound (C 18 H 19 BrFN 3 S) as fine colourless crystals (m.p. 577-579 K). Single crystals suitable for X-ray diffraction were obtained by slow evaporation of a solution of the title compound in EtOH/ CHCl 3 (1:2, v/v) at room temperature. 1

Figure 6
The reaction scheme yielding compound I.

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Acta Cryst. Program(s) used to solve structure: SIR2011 (Burla et al., 2012); program(s) used to refine structure: SHELXL (Sheldrick, 2015); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012), Mercury (Macrae et al., 2008), SCHAKAL (Keller, 1989), DIAMOND (Brandenburg, 2006); software used to prepare material for publication: WinGX (Farrugia, 2012), PARST (Nardelli, 1995), publCIF (Westrip, 2010), enCIFer (Allen et al., 2004) and PLATON (Spek, 2009). where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.62 e Å −3 Δρ min = −0.36 e Å −3 Absolute structure: Flack (1983) Absolute structure parameter: 0.50 (2) 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.