A quantum chemical study of lead(II) thiocomplexes with mono- and bidentate ligands

Abstract

Model Pb(II) thiocomplexes with mono- and bidentate ligands of the composition [Pb(L1,2)n]2−n (L1 is (SC6H5)− (thiophenolate ion), L2 is (S2CN(CH3)2)− (dithiocarbamate ion), n is the number of ligands of 2–6), which simulate fragments of the crystal structures of Pb(II) complex compounds with organic ligands, are studied within density functional theory. Geometric and energy parameters of model complexes with different coordination geometries of the Pb atom are determined and the stereochemical activity of the lone electron pair (LEP, E) of the Pb2+ ion is estimated in them. In the studied complexes, the highest Pb-S binding energy is found for the Pb atom surrounded by 2–4 ligands. The geometry of the Pb atom coordinated by S donor atoms can be described in terms of the valence shell electron pair repulsion (VSEPR) model with stereochemically active LEP. The coordination number (cn) of the Pb atom in the most energetically favorable complexes [Pb(SC6H5)n]2−n is (3+E) − (4+E), and in [Pb(S2CN(CH3)2)n]2−n complexes, it is (4+E) and (6+E). Configurations with the mentioned cns are most often observed in the crystal structures of Pb(II) thiocomplex compounds.