X-ray crystallographic analysis of the structural distortions induced by substitution and annulation of the dodecahedrane nucleus.

Methyl dodecahedranecarboxylate, C22H22-O2, (4), Mr = 318.42, monoclinic, C2/c, a = 12.600 (2), b = 7.992 (4), c = 28.975 (7) A, beta = 101.79 (2) degrees, V = 2856 A3, Z = 8, Dx = 1.48 g cm-3, lambda(Mo K-alpha) = 0.71073 A, mu = 0.84 cm-1, F(000) = 1360, T = 294 K, R = 0.044 for 2109 unique reflections with Fo2 greater than 3 sigma(Fo2). 21-Phenylcyclopropadodecahedrane, C27H24, (5), Mr = 348.49, tetragonal, P4(2)/n, a = 17.528 (3), c = 10.752 (2) A, V = 3303 A3, Z = 8, Dx = 1.40 g cm-3, lambda(Mo K-alpha) = 0.71069 A, mu = 0.85 cm-1, F(000) = 1488, T = 295 K, R = 0.053 for the 1773 unique reflections with Fo2 greater than 1 sigma(Fo2). The molecular geometries of methoxycarbonyldodecahedrane (4) and 21-phenylcyclopropadodecahedrane (5) are compared to those of the parent C20H20 hydrocarbon (1) and its 1,16-dimethyl derivative (2). For both (2) and (4), the framework is modestly distorted by the substituents, the intracavity distance being more extended along the axis that contains the pendant group(s). Remarkably for (5), its cyclopropane ring has all C-C bonds and internal angles essentially equal, and those dodecahedrane bonds in the immediate vicinity of the ring fusion are extensively perturbed.