Palladium K-edge XAS studies on Controlled Ligand Systems

X-ray absorption spectroscopy (XAS) is widely used across life and physical sciences to identify the electronics and structure surrounding a specific element. XAS is less often used for characterization of organometallic compounds, especially for sensitive and highly reactive species. In this study, we used solid- and solution-phase XAS to compare a series of related 25 palladium complexes in controlled lig-and environments. The compounds include palladium centers in the formal I, II, III, and IV oxidation states, supported by tridentate and tetradentate macrocyclic ligands, and different halide and methyl lig-and combinations. Based on the analysis of the K-edge energies, it was observed that these energies in-crease not only upon oxidation of the metal center, but also upon increasing the denticity of the ligand framework, substituting sigma-donating methyl groups with chlorides, and increasing the charge of the overall metal complex by replacing charged ligands with neutral ligands. Subsequently, these trends were applied to characterize compounds whose oxidation states were otherwise unconfirmed.