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, C(18)H(19)FN(2)O (I) and C(18)H(19)ClN(2)O (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 R (2) (2)(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[Image: see text]).