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 NH₃; 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.