2,4-Dioxa-λ⁶-thia­tetra­cyclo­[5.3.1.1^5,9.0^1,5]dodecane-3,3-dione

The crystal structure of the title compound, C₉H₁₂O₄S, was determined in order to investigate the effect of the eclipsed O atoms on the bond length of the vicinal quaternary C atoms. The two quaternary C atoms of the noradamantane skeleton and the two O atoms to which they are connected all located essentially in the same plane (maximum deviation = 0.01 Å), resulting in an eclipsed conformation of the C—O bonds. The C—C bond of the quaternary C atoms is 1.581 (3) Å, considerably longer than the other C—C bonds of the mol­ecule due to the stretch of the cage structure.

Penta­cyclo­[9.3.1.1^2,6.1^4,8.1^9,13]octa­deca-1(2),8(9)-diene

The title compound, C₁₈H₂₄, was the main product of thermolysis of noradamantene dimer (hepta­cyclo­[9.3.1.1^2,6.1^4,8.1^9,13.0^1,9.0^2,8]octa­deca­ne). The crystal structure was determined to prove that the thermolysis product of noradamantene dimer is favored by stretch release due to ring opening of the four-membered ring. The bond length of the quaternary C atoms of the starting material was calculated as 1.6 Å, enlarged in comparison to other single bonds. After the rearrangement, the stretch release of the above carbons leads to an increase of the distance between them (2.824 Å) with respect to the crystallographic data.

2,9-Diiodo­hexa­cyclo­[9.3.1.1^2,6.1^4,8.1^9,13.0^1,8]octa­deca­ne

The title compound, C₁₈H₂₄I₂, has an adamantanoid structure with tetra­hedral cages having four C atoms lying on the same plane [(I—)C—C—C—C(—I) torsion angle = 0°]. The plane is extended by the two I atoms, each having a deviation of 1.0 (6) Å [C—C—C—I torsion angle = 178.9 (4)°]. The central C—C bond connecting the two quaternary carbons seems enlarged [1.593 (9) Å] in comparison to the corresponding bond in [2]diadamantane [1.554 (3) Å]. This is attributed to the presence of the electronegative I atoms, which affect inductively the C atoms of the four-C-atom plane, making the central C—C bond weaker.