Theoretical Study on the Electronic Structure of Fe(0)–, Pd(0)–, and Pt(0)–Phosphine–Carbon Dioxide Complexes

The activation of carbon dioxide by transition metal complexes is a fundamental process in catalysis and carbon capture. In this study, density functional theory (DFT) calculations, combined with Quantum Theory of Atoms in Molecules (QTAIM) and Natural Orbitals for Chemical Valency (NOCV) analyses, were employed to investigate the bonding characteristics and electronic structure of Fe(0)–, Pd(0)–, and Pt(0)–phosphine complexes with CO2. The Fe(0) complexes exhibited the strongest CO2 activation, characterized by substantial C=O bond elongation, significant charge transfer, and strong π-backdonation. In contrast, Pd(0) complexes showed minimal CO2 activation, while Pt(0) complexes displayed intermediate behavior. The electronic effects of phosphine ligands were also analyzed, revealing that electron-donating phosphines enhance CO2 activation, whereas electron-withdrawing phosphines weaken metal–CO2 interactions. These findings provide key insights into the design of transition-metal-based catalysts for CO2 conversion and utilization.