Chemical interaction study between xanthate ligand and lead (II) using NBO, EDA and QTAIM analysis

Abstract

As a useful flotation agent, the xanthate ligand, O-alkyldithiocarbonates, has been used by different countries by its easy and inexpensive synthesis. More recently papers explored many different applications using this ligand within a complex of several metals cation. In order to study the proprieties of the lead (II) complex with such ligand, the object of this work is to provide a better understanding of the Pb-S bond using different theoretical approaches as NBO, EDA and QTAIM analysis and the influence caused by the different alkyl groups of the ligand. By an optimized structure, the NBO showed that the Pb-S is mainly composed by p orbital of the lead and by the p lone pair of the sulfur atom. The calculation with different alkyl groups highlights that the presence of a larger hydrocarbon chain provides a higher contribution of the s orbital of the lead atom to the interaction. Through the EDA analysis, the interaction between ligand and metal has the predominance of an electrostatic character. The size of the alkyl group has an impact on the value of both covalent and electrostatic character, making the interaction more covalent, due to a higher presence of an electronic density on sulfur atom. This density can be evaluated by the topological study of the QTAIM analysis, which enhances the fact that the charge over the sulfur atom gets higher when using a larger alkyl group for the xanthate ligand.