Holo- and hemidirected coordination spheres in a novel three-dimensional polymeric (KPbII)-Pb-I heteropolynuclear complex: X-ray crystal structure of [KPb(AcO)(2)(SCN)](n)

A novel three-dimensional polymeric (KPbII)-Pb-I heteropolynuclear complex, [KPb(AcO)(2)(SCN)](n), with mixed acetate and thiocyanate ligands, has been synthesized and characterized. Its single-crystal X-ray structure (Fig. 1) shows three types of K+ ions with coordination numbers of seven, and three types of Pb2+ ions with coordination numbers of eight, eight, and nine, respectively. The Pb centers (Pb(1) and Pb(3); Fig. 1) with coordination numbers of nine and eight, respectively, possess stereochemically 'inactive' electron lone pairs, and the coordination sphere is holodirected. However, the arrangement of O-, N-, and S-atoms for the eight-coordinated Pb(2) suggests a gap or hole in the coordination geometry around this atom. This 'hole' is possibly occupied by a stereochemically 'active' electron lone pair of Pb(2), and its coordination sphere is, thus, hemidirected.