CRYSTAL-STRUCTURES OF 3,5,5'-TRICHLORO-2,2'-BITHIOPHENE AND 3,3',5,5'-TETRACHLORO-2,2'-BITHIOPHENE

The crystal structures of 3,5,5'-trichloro-2,2'-bithiophene (I) and 3, 3',5,5'-tetrachloro-2,2'-bithiophene (II) have been determined by sing le crystal X-ray diffraction techniques. Both I and II crystallize in the monoclinic crystal system. For I, a = 3.895(2), b = 11.928(2), c = 10.701(2) angstrom, beta = 97.70(1)-degrees, space group P2(1), Z = 2 and for II, a = 8.942(2), b = 3.900(2), c = 15.180(2) angstrom, beta = 92.30(1)-degrees, space group P2(1)/n, Z = 2. The structures have be en solved by direct methods and all nonhydrogen atoms refined with ani sotropic thermal parameters. For I the final residual is 0.035 (all 11 85 independent reflections, MoKalpha radiation) and for II, 0.034 (all 1209 independent reflections, MoKalpha radiation). Both I and II have the anti conformation but I has a torsion angle of 3.4(5)-degrees bet ween the two thiophene rings while II is completely planar.