Insight Into the Intermolecular Factors Responsible for the Z , Z Configuration of Ar–X–N=S=N–X–Ar (X = S, Se) Derivatives in the Solid State

The molecular and crystal structures of three new derivatives of Ph–S–N=S=N–S–Ph (1), with 2,4,6-(tert-C4H9)3C6H2 (4), C6F5 (5) and 4-CF3C6F4 (6) as peripheral rings, respectively, and one new derivative of Ph–Se–N=S=N–Se–Ph (2), with C6F5 (7) as peripheral rings, are reported and discussed in connection with those of the two parent structures 1 and 2 and those of the previously studied derivative of 1 containing 4-ClC6H4 (3) as peripheral rings. For these seven compounds the Z,Z configuration is the only one of the three theoretically possible configurations observed in the solid state and this configurational preference can not be explained by intramolecular stereoelectronic effects. Calculation of the packing energies and densities for the six most common space groups revealed that the crystal packing of the parent structure 1 in the Z,Z configuration has a systematic preference over the corresponding packing of 1 in the Z,E configuration by 0.3–4.9 kJ mol–1. As a result, packing forces are most likely responsible for the dominance of the Z,Z configuration of the title compounds in the crystal.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)