Quantitative Descriptions of Dewar-Chatt-Duncanson Bonding Model: A Case Study of Zeise and Its Family Ions

Historically, Dewar-Chatt-Duncanson (DCD) model is a heuristic device to advance the development of organometallic chemistry and deepen our understanding of the metal-ligand bonding nature. Zeise's ion, the first man-made organometallic compound and a quintessential transition metal-olefin complex, was qualitatively explained using the DCD bonding scheme in 1950s. In this work, we quantified the explicit contributions of the sigma donation and pi back-donation to the metal-ligand bonding in Zeise and its family ions, [PtX3L](-) (X=F, Cl, Br, I, and At; L=C2H4, CO, and N-2), using state-of-the-art quantum chemical calculations and energy decomposition analysis. The relative importance of the sigma donation and pi back-donation depends on both X and L, with [PtCl3(C2H4)](-) being a critical case in which the sigma donation is marginally weaker than the pi back-donation. The changes along this series are controlled by the energy levels of the correlated molecular orbitals of PtX3- and ligand L. This study deepens our understanding of the bonding properties for transition metal complexes beyond the qualitative description of the DCD model.

Automated summary

The Dewar-Chatt-Duncanson (DCD) model is a heuristic tool to advance the development of organometallic chemistry and deepen our understanding of metal-ligand bonding. In this study, we quantified the contributions of sigma donation and pi back-donation to the metal-ligand bonding in Zeise and its family ions using state-of-the-art quantum chemical calculations. The relative importance of sigma donation and pi back-donation depends on the specific ligands and halogen atoms, and the energy levels of relevant molecular orbitals play a crucial role in controlling these contributions.