Crystal structures and Hirshfeld surface analysis of 2-(adamantan-1-yl)-5-(4-fluoro-phen-yl)-1,3,4-oxa-diazole and 2-(adamantan-1-yl)-5-(4-chloro-phen-yl)-1,3,4-oxa-diazole.

The crystal structures of the title adamantane-oxa-diazole 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-oxa-diazole unit. The mol-ecular 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, mol-ecules are linked by pairs of C-H⋯N hydrogen bonds, forming inversion dimers with R 2 2(12) ring motifs. In (I) the dimers are connected by C-H⋯F inter-actions, forming slabs lying parallel to the bc plane. In (II), the dimers are linked by C-H⋯π and offset π-π inter-actions [inter-planar distance = 3.4039 (9) Å], forming layers parallel to (10).