The Crystal and Molecular Structure of Perchloro-(4, 8-dimethylenetricyclo3. 3. 2. 01,5deca-2, 6-diene)

Abstract The molecular structure of the compound of the formula C12Cl12, mp 273°C, obtained on the pyrolysis of perchloro-(3, 4-dimethylenecyclobutene) at about 250°C, has been determined by a three-dimensional X-ray crystal analysis. The crystal of the compound is monoclinic with four molecules in the unit cell of the dimensions a=16.78, b=6.80, c=17.10 Å and β=116.5°; the space group is C2⁄c. The positions of all the chlorine atoms were elucidated by using the minimum function method, and then those of all the carbon atoms were obtained from an electron density distribution calculated with the phases of chlorine atoms alone. The positional parameters of all the atoms thus obtained were refined by the block-diagonal matrix least-squares method with anisotropic temperature factors. The final discrepancy factor R is 0.094 excluding zero intensity data. As a result of the present study, it is concluded that the compound is perchloro-(4, 8-dimethylene-tricyclo3.3.2.01,5deca-2, 6-diene). Except the contacts between the chlorine atoms attached to the same carbon atom, there are several intramolecular Cl···Cl contacts with distances smaller than twice the ordinary van der Waals radius of the chlorine atom; i.e., 3.06, 3.12, 3.13, 3.18 and 3.32 Å. However, it is found that these very close contacts do not seriously affect the bond lengths and angles in the molecule.