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In the crystal of octamethylcuneane (1,2,3,4,5,6,7,8-octamethylpentacyclo[3.3.0.0 2,4 .0 3,7 .0 6,8 ]octane), C 16 H 24 , there are two independent molecules in the asymmetric unit. Octamethylcubane(1,2,3,4,5,6,7,8-octamethylpentacyclo[4.2.0.0 2,5 .0 3,8 .0 4,7 ]octane), C 16 H 24 , exhibits crystallographic 3m symmetry. Due to the eclipsed orientation of the methyl groups in octamethylcubane, the average bond length is extended to 1.563 (3) A compared with cubane itself. In the cuneane derivative, the cage bond lengths vary between 1.517(2) and 1.573(2)A in accordance with their bicyclic character and the repulsive forces between the methyl groups. The exocyclic bonds to the methyl C atoms in both molecules are shortened due to the increased s character of the cage C atoms.

In the crystal, dimethyl pentacyclo[4.2.0.0 2,5 .0 3,8 .0 4,7 ]-octane-1,4-dicarboxylate, C 12 H 12 O 4 , has crystallographic 2/m symmetry. The carbonyl group takes an eclipsed orientation with respect to the skeleton bond C1-C3, as well as to the methoxy O2-C5 bond. The ester group is tilted in the direction of the opposite C atom C3 about its staggered orientation relative to the skeleton bonds C1-C2 and C1-C2'. The valence angles within the ester group, C4-O2-C5, O1-C4-C1 and O1-C4-O2, are expanded to 116.9 (2), 126.2 (2) and 123.5 (2)°, respectively. These enlargements cause a narrowing of the bond angle O2-C4-C1 to 110.4 (2)°