CRYSTAL AND MOLECULAR-STRUCTURES OF HYPERVALENT THIA SELENA-PENTALENES/

X-Ray structure analyses were performed on the ,4-dimethylene-2,5-bis( 4-chlorophenylimino)-1,6,6a lambda(4)-trithia-3,4-diazapentalene (5), 2,5-bis(4-chlorophenylimino)-6a lambda(4)-thia-1,6-diselena-3,4-diazap entalene derivative (6) and 2,5-bis(phenylimino)-1,6-dithia-6a lambda( 4)-selena-3,4-diazapentalene derivative (7). The lengths of the S-S bo nds (mean value of 2.401 Angstrom) for 5 and those of the Se-S bonds ( mean value of 2.501 Angstrom) for 6 and 7 are longer than that of the normal S-S or Se-S single bond (2.08 and 2.21 Angstrom for S-S and Se- S bonds, respectively) by about 15%, which shows the hypervalent chara cter of these S-S or Se-S bonds. In molecule 5, a difference in the tw o S-S bonds (2.488 and 2.314 Angstrom) is considered to be a reflectio n of the feature of a weak hypervalent bond, which is very liable with effects of the environment such as substituents or packing. The same tendency was observed for molecule 6. The crystal structures of 5 and 6, both of which are p-Cl-phenylimino derivatives, are isomorphous wit h each other. The crystal structure of 7, a phenylimino derivative, is different from those of 5 and 6, and two Se-S bonds of 7 are almost s imilar. The diffraction intensities of 5 were measured by a Weissenber g-diffractometer with imaging-plates, because only Very small crystals were obtained, the intensities of which could not be measured by a co nventional four-circle diffractometer with a rotating anode generator.