Chemistry of subvalent main group metals with dithiolates. Part 2. X-Ray structural, thermal, and theoretical investigations on the novel one-dimensional stacking structure K ₂ [Pb{S ₂ CC(CN) ₂ } ₂ ]·2H ₂ O

The structure of K2[Pb{S2CC(CN)2}2]·2H2O has been determined from 673 reflections of a twinned crystal and refined to an R factor of 0.094 (R′= 0.085) It consists of one-dimensional [Pb{S2CC(CN)2}2]2– anions stacked along the crystallographic b direction with Pb … Pb 4.074 Å and interspersed K+ cations. The anion has a pyramidal geometry with Pb at the top exhibiting an apparently stereochemically active lone pair. By use of relativistic Hartree–Fock molecular orbital calculations it is shown that the pyramidal geometry is 25 kcal mol–1(104.6 kJ mol–1) more stable than a planar arrangement. Within the stack there is no significant interaction between the anions.