CRYSTAL AND MOLECULAR-STRUCTURE OF Z-1,2-DICHLORO-1,2-BIS(2-CHLOROPHENYL)ETHYLENE AND E-1,2-DICHLORO-1,2-BIS(2-CHLOROPHENYL)ETHYLENE - AN X-RAY AND NMR-STUDY

The crystal structures of the title compounds were determined by singl e crystal X-ray diffraction techniques. The molecule of the Z isomer, which crystallizes in the monoclinic space group C2/c with Z = 4 in a cell of dimensions a = 14.891(2), b = 10.780(2), c = 8.769(1) Angstrom , beta = 97.47(2)degrees, V = 1395.7(7) Angstrom(3), has crystallograp hic twofold symmetry. The E form crystallizes in the orthorhombic spac e group Pbca with a = 11.730(1), b = 6.932(1), c = 16.841(1) Angstrom, V = 1369.4(2) Angstrom(3), and Z = 4, Its molecules have crystallogra phically dictated 1 symmetry. In both isomers the phenyl rings are rou ghly perpendicular to the average ethylene plane. The atoms characteri zing this plane show significant deviations from planarity in the Z is omer. Marked bond-angle distortions at the ethene carbons of both stru ctures are observed. The H-1 and C-13 NMR spectra of the compounds wer e measured and, particularly in the case of the H-1 chemical shifts, f all into two quite separate spectral regions. At low temperature, two conformational isomers, those with different relative orientation of t he C-Cl bonds of the phenyl rings, are observed in the spectrum of eac h compound.