Crystal structures and Hirshfeld surface analysis of 2-(adamantan-1-yl)-5-(4-fluorophenyl)-1,3,4-oxadiazole and 2-(adamantan-1-yl)-5-(4-chlorophenyl)-1,3,4-oxadiazole

The crystal structures of the title adamantane-oxadiazole hybrid compounds, C18H19FN2O (I) and C18H19ClN2O (II), are built up from an adamantane unit and a halogenophenyl ring, [X = F (I), Cl (II)], in position 5 on the central 1,3,4-oxadiazole unit. The molecular structures are very similar, only the relative orientation of the halogenophenyl ring in comparison with the central five-membered ring differs slightly. In the crystals of both compounds, molecules are linked by pairs of C—H...N hydrogen bonds, forming inversion dimers with R22(12) ring motifs. In (I) the dimers are connected by C—H...F interactions, forming slabs lying parallel to the bc plane. In (II), the dimers are linked by C—H...π and offset π–π interactions [interplanar distance = 3.4039 (9) Å], forming layers parallel to (10\overline{1}).