On the nature of the bonding of lone pair ligands to a transition metal

Abstract

We report an analysis of the interaction of the closed shell, lone pair ligands CO, NH3 and PF3 with a Cu surface. The surface is represented by one and by five atom clusters. The interaction is analyzed with the constrained space orbital variation, CSOV, method which leads to a division of the interaction into several steps and permits an unambiguous assignment for the energetic importance of each step. The importance of the σ repulsion between the ligand lone pair and the metal is demonstrated and the significance of the dipole moment of the ligand is shown. The charge rearrangements are divided into intra-unit polarization and inter-unit donation between the units. Formation of covalent chemical bonds is not particularly important for NH 3; the bonding can be viewed as electrostatic and arising because of the large NH3 dipole moment. For CO and PF3, covalent bonds are formed by metal to ligand π donation; for CO, the relative importance of dπ and valence 4pπ for this bonding is examined. © 1984 American Institute of Physics.