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Peculiarities of chemical bonding in crystalline 3-isopropyl-4-thiomethyl-N6-benzoylsidnone imine with four independent molecules were investigated by means of R. Bader's ''Atoms in Molecule'' theory. For the fist time the pseudosymmetry phenomenon was explored at both the molecular (charge density within the molecular species) and supramolecular (network of intermolecular interactions) level.''Pseudosymmetry'' is the spatial arrangement of species that feigns symmetry without fulfilling it. 1 A classical example is the crystalline tolan, where the local symmetry element (pseudo-2 1 -axis) between its two crystallographically nonequivalent species was fist identified. 2 Since then, crystals with several independent molecules in an asymmetric unit and in general the phenomenon of pseudosymmetry have been subject of a vast number of studies. Usually the search for an explanation of the occurrence of such systems (e.g. with Z 0 > 1) has been based on the statistical analysis of various crystal structures. 3-10 Using this approach, several principles governing the formation of structures with Z 0 > 1 were derived (dense packing and H-bonding requirements, 4,6,10 strength of the chemical binding between independent molecules 11 ). However, the degree of similarity between independent molecules was only a minor point of the study. Comparison of the geometrical parameters was mainly used to estimate to what extent the chemically identical but symmetry independent moieties are identical.A more powerful approach is the analysis of the electron density distribution function r(r) in a crystal 12-14 within the ''Atoms in Molecules'' theory proposed by Bader. 15 It allows a comparison of the topological characteristics of chemical bonds, atomic charges and volumes, and is substantially more sensitive to the difference in the intermolecular interaction patterns as compared to the classical approach based on the comparison of geometric parameters. However, charge density studies of such crystals are scarce and limited to systems with only two independent molecules. 16-22 Moreover, in the majority of investigations the two species were a priori assumed to be fully identical and additional constaints were applied to their electron densities. The others demonstrated that the r(r) distributions within independent molecules are different due to the variation of their bonding patterns, although with no quantitative description of the latter. 20,22 ; Fax: +495 135 5085; Tel: +495 135 9214 † Electronic supplementary information (ESI) available: Additional experimental details. CCDC reference number 737013. For ESI and crystallographic data in CIF or other electronic format see

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