The crystal structures of two isomers of 2-(thienyl)glyoxime, 2-thienylethanedial dioxime, C6H6N202S, E,E [orthorhombic, Pbca, a= 11.074 (5), b= 9.152 (3), c = 14.660 (4)/k, V = 1185.84/k 3, Dx = 1.522 g cm -3, Z = 8, R = 0.058 for 1276 reflections with I> 3o-(1)] and E,Z [monoclinic, P2/c, a = 12.189 (3), b = 3.865 (3), c= 16.022 (5) A, /3 = 90.79 (2) '~, V = 754.8/k 3, Dx = 1.498 g cm-3, Z = 4, R = 0.032 for 1154 reflections with I> 30-(1)] have been determined. An analysis, based on the structures of the title compounds and on other glyoxime derivatives showed that the E,E-configuration is the preferred form. A statistical study on the geometry of the oxime group and on hydrogen bonding in the oximes was performed using the Cambridge Structural Database. The crystal structure of two isomers of 2-(thienyl)glyoxime ExperimentalThe E,E-and E,Z-isomers of 2-(thienyl)glyoxime were prepared by recrystallization from dichloromethane and methanol, respectively. Crystal data for the two isomers of 2-(thienyl)glyoxime and details of the data collection and refinement procedures are summarized in Table 1. The lattice parameters were obtained from angular settings of 25 well-centred,

The hydrogen-bond acceptor characteristics of sulfate dianions are analyzed in crystal structures of small molecules. For 85 anions, neither coordinated to metal ions nor covalently bonded, 697 hydrogen bonds are faund. Of these, 266 (38%) are the O...H--O type and 431 (62%) are the O.-.H--N type, proportions that correspond well to the stoichiometry of the compounds studied and indicate no preference for a particular donor. The analysis of the data set, after classifying the hydrogen bonds according to the different types of donors, shows that O.-.H--O bonds are more linear than O...H--N. The anion oxygen-acceptor function is characterized by multiple hydrogen bonding. Only in 56 cases does a sulfate oxygen participate in a single hydrogen bond. In most cases every sulfate oxygen is coordinated by two (187 cases) or three (89 cases) hydrogen bonds. For three H donors, the preferred coordination geometry of the sulfate oxygen is pyramidal. The most frequent coordination around a sulfate dianion is with eight to ten H donors. Thus, sulfate dianions can play a significant cohesive role in molecular aggregation.

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The title compounds (III) (X‐ray analysis for (IIIa): space group P21/c; Z=4) are prepared.

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