3-(Adamantan-1-yl)-4-(prop-2-en-1-yl)-1H-1,2,4-triazole-5(4H)-thione

The title molecule, C15H21N3S, exists as the thione tautomer in the solid state. The 1,2,4-triazole ring is almost planar (r.m.s. deviation = 0.004 Å) and the prop-2-en-1-yl chain is close to being perpendicular to this plane [C—N—C—C torsion angle = 77.1 (5)°]. In the crystal, centrosymmetric dimeric aggregates are formed by pairs of N—H⋯S hydrogen bonds as parts of eight-membered (⋯HNCS)2 synthons. These are connected into layers parallel to (101) via C—H⋯π interactions, where the π-system is the triazole ring. The investigated sample was a nonmerohedral twin; the refined domain ratio was 0.655 (4):0.345 (4).

Herein, the crystal and molecular structure is described which was performed to determine the tautomeric form of (I).
The key result of the structure determination of (I) is the confirmation of the thione form of the molecule, Fig. 1. The 1,2,4-triazole ring is planar [r.m.s. deviation = 0.004 Å] and the S1 atom lies 0.060 (1) Å out of this plane. The C13 atom lies even further out of the plane, i.e. by 0.155 (4) Å in the opposite direction to the S1 atom. The prop-2-en-1-yl chain is almost perpendicular to the plane through the five-membered ring as seen in the value of the C1-N1-C13-C14 torsion angle of 77.1 (5)°. The terminal ethene bond is directed toward the adamantyl group.
In the crystal packing, centrosymmetric dimeric aggregates are formed by N-H···S hydrogen bonds via eightmembered {···HNCS} 2 synthons. These are connected into a two-dimensional array parallel to (101) via C-H···π interactions, where the π-system is the triazole ring, Fig. 2 and Table 1. Layers stack without specific intermolecular interactions between them, Fig. 3.

Experimental
A mixture of adamantane-1-carbohydrazide (1.94 g, 0.01 mol) and allyl isothiocyanate (0.99 g, 0.01 mol), in ethanol (10 ml) was heated under reflux with stirring for one hour and the solvent was distilled off in vacuo. Aqueous sodium hydroxide (10%, 15 ml) was added to the residue and the mixture was heated under reflux for 2 h then filtered hot. On cooling, the mixture was acidified with hydrochloric acid and the precipitated crude product was filtered, washed with water, dried and crystallized from aqueous ethanol to yield 2.18 g (79%) of (I) as colourless prisms. m.p.

Refinement
Carbon-bound H atoms were placed in calculated positions [N-H = 0.88 Å and C-H = 0.95 to 1.00 Å, U iso (H) = 1.2U eq (N, C)] and were included in the refinement in the riding model approximation.
A sphere of reflections was measured, which should be sufficient to refine the non-merohedral twinned structure.
However, separating the reflection data into two domains did not lead to an improvement in the refinement, and this was Two reflections, i.e. (10 3 5) and (5 0 1), were omitted owing to poor agreement.

Figure 1
The molecular structure of (I) showing displacement ellipsoids at the 50% probability level.    where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.71 e Å −3 Δρ min = −0.66 e Å −3 Special details Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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.