The title compound, C16H24Cl2O, was synthesized from β-himachalene (3,5,5,9-tetra­methyl-2,4a,5,6,7,8-hexa­hydro-1H-benzocyclo­heptene), which was isolated from the essential oil of the Atlas cedar (cedrus atlantica). The mol­ecule forms an extended sheet of two fused rings which exhibit different conformations. The six-membered ring has a half-chair conformation, while the seven-membered ring displays a chair conformation; the dihedral angle between the two rings is 38.2 (1)°.

In the title hydrated mol­ecular salt, [Fe(C12H8N2)3](C9H5N4O)2·0.5H2O, the water mol­ecule site is half-occupied. The Fe—N bond lengths within the octa­hedral tris-chelate [Fe(phen)3]2+ ion (phen is 1,10-phenantroline) are indicative of a low-spin d 6 electronic configuration for the metal ion. The C—N, C—C and C—O bond lengths in the polynitrile anions indicate extensive electronic delocalization. In the crystal, the components are linked through O—H⋯N hydrogen bonds, forming [100] chains, as well as through Coulombic inter­actions.

Single crystals of α-Ba2P2O7, dibarium diphosphate, were obtained by solid-state reaction. The ortho­rhom­bic structure is isotypic with α-Sr2P2O7 and is the second polymorph obtained for this composition. The structure is built from two different BaO9 polyhedra (both with m symmetry), with Ba—O distances in the ranges 2.7585 (10)–3.0850 (6) and 2.5794 (13)–2.9313 (4) Å. These polyhedra are further linked by sharing corners along [010] and either edges or triangular faces perpendicularly to [010] to form the three-dimensional framework. This polyhedral linkage delimits large channels parallel to [010] where the P2O7 diphosphate anions are located. These groups (symmetry m) are characterized by a P—O—P angle of 131.52 (9)° and an eclipsed conformation. They are connected to the BaO9 polyhedra through edges and corners.