Electronic structures of cyclometalated palladium complexes in the higher oxidation states

The electronic and redox properties of a series of cyclometalated Pd complexes with oxidation states of +2, +3 and +4 were examined using a range of currently available spectroscopic and electrochemical techniques. Changes in metal–ligand bond lengths were established by X-ray crystallography and correctly predicted by DFT calculations, from which the frontier orbitals and partial atomic charges can be obtained. X-ray absorption spectroscopy (XAS) revealed interesting XANES features that suggest a synergistic relationship between metal–ligand interactions. The electrochemical study of the Pd(II) dimer was found to contain two sequential oxidative potentials indicative of a weak metal–metal interaction.