| Summary: | Three homoleptic Hg(S<sub>2</sub>CNR<sub>2</sub>)<sub>2</sub>, for R = ethyl (<b>1</b>), isobutyl (<b>2</b>), and cyclohexyl (<b>3</b>), compounds apparently exhibit a steric-dependent supramolecular association in their crystals. The small group in <b>1</b> allows for dimer formation via covalent Hg–S interactions through an eight-membered {–HgSCS}<sub>2</sub> ring as the dithiocarbamato ligands bridge centrosymmetrically related Hg atoms; intradimer Hg···S interactions are noted. By contrast, centrosymmetrically related molecules in <b>2</b> are aligned to enable intermolecular Hg···S interactions, but the separations greatly exceed the van der Waals radii. The large group in <b>3</b> precludes both dimerization and intermolecular Hg···S interactions. Computational chemistry indicates that the potential region at the Hg atom is highly dependent on the coordination geometry about the Hg atom. Intramolecular (<b>1</b>) and intermolecular (<b>2</b>) spodium bonding (SpB) is demonstrated. Even at separations approaching 0.4 Å beyond the sum of the assumed van der Waals radii, the energy of the stabilization afforded by the structure directs SpB in <b>2</b> amounts to approximately 2.5 kcal/mol. A natural bond orbital (NBO) analysis points to the importance of the LP(S) → σ*(Hg–S) charge transfer and to the dominance of the dispersion forces and electron correlation to the SpB in <b>2</b>.
|
|---|