On the origin of the hemidirected geometry of tetracoordinated lead(II) compounds

Abstract

Abstract In order to explain the difference between high-symmetric holodirected and less-symmetric hemidirected Pb(II) compounds, the structures of [PbF 4 ] 2− , [PbCl 4 ] 2− and [Pb(OH) 4 ] 2− have been optimized without any symmetry restrictions and/or within various symmetry groups using all-electron relativistic B3LYP treatment and alternatively using B3LYP and MP2 treatments with effective core potential for Pb atoms. Optimal geometries of both [PbF 4 ] 2− and [PbCl 4 ] 2− are of T d symmetry (holodirected structures). The [Pb(OH) 4 ] 2− optimal geometry of C 2 symmetry cannot be explained by pseudo-Jahn–Teller effect due to energy and symmetry reasons. The less-symmetric geometry of tetracoordinated Pb(II) complexes with non-halogen ligands may be explained by the mutual interactions of their less-symmetric ligands. This symmetry decrease is subsequently supported by the increasing p electrons content in the Pb(II) lone electron pair via influencing the hybridization scheme of the Pb–ligands bond orbitals (i.e. not due to the repulsion between the ligands and the Pb(II) lone electron pair).