The crystal structure of the 1:1 complex of [3.3]paracyclophane with tetracyanoethylene

Tetracyanoethylene (TCNE) and [3.3]paracyclophane (PC) form a 1:1 complex, C6N4. C18H20, that crystallizes in P]', with a=8533, b=8538, c=7705 A, ~=10333, fl=110.78, 7=10401 °, and one formula unit in the unit cell. The structure was solved by the study of Patterson sections, calculated from three-dimensional diffractometer data, and was refined by full-matrix least-squares methods to R= 0055 for 1634 reflections. Molecules are stacked in columns along the [111] direction, which is the needle axis of the crystal, with the TCNE and aromatic ring planes approximately parallel to each other. The geometry of the PC molecule is not significantly different from that in crystals of uncomplexed PC, except for a slightly greater mutual parallel displacement of the rings. TCNE is disordered by rotation about an axis through its center and normal to its plane; two orientations occur with relative weight about 3:1. Other orientations appear to be prohibited by potentially very short N . . . H and N . . . C contacts between adjacent columns of molecules.