Etudes Structurales en Relation Avec le Concept de Substitution “Capto-Dative” III. Structures de Cinq Dehydrodimères de Formule R1R2CH-CHR2R1

From X-ray diffractometry molecular structure of five 2,3-bis(disubstituted)-butanedinitrile or-dimethylsuccinate have been determined. The aim of this study is to analyse the effects of capto-dative substitution on molecular deformation in compounds with tertiary central carbon atoms. (I) meso 2,3-bis (dimethylamino) butanedinitrile, C8H14N4 is monoclinic, P21/α with α=10.545(5), b=6.314(2), c=7.943(3)A, B=109.25(3)°, V=499.3(3)A3, Z=2. (II) meso 2,3-bis(methylthio) dimethylsuccinate, C8H14S2O4, is triclinic, P1 with α=8.349(2), b=5.761(1), c=7.928(2)A, α=71.85(2), β=113.12(2), γ=74.41 (2)°, V=298.0(1)A3, Z=1. (III) dl 2,3-bis(phenylthio)dimethylsuccinate, C18H18S2O4, is orthorhombic, Pbnb with α=15.265(3), b=16.618(4), c=7.063(2)A, V=1791.7(6)A3, Z1 (III) dl 2,3-diphenoxy dimethylsuccinate, C18H18O6 is orthorhombic, Pcab with α=21.612(6), b=17.662(4), c=9.029(2)A, V=3446.5(6)A3, Z=8. (V) dl 2,3-diacetoxy dimethylsuccinate, C18H14O8, is orthorhombic, Pca21, with α=10.879(2), b=13.558(2), α=9.133(2)A, V=1347.1(5)A3, Z=4. The geometry of the five molecules is quite normal. These results are compared with those concerning dimers with quaternary central carbon atoms (R1R2R3C)2 in which a long central C-C bond was found.