Electronic Structures of the Palladium(II) Complexes with Redox-Active o-Phenylenediimines

The electronic structures and the character of the electron density redistribution in the palladium complexes with the redox-active ligands in the oxidized and nonoxidized forms are studied by X-ray photoelectron spectroscopy. According to the photoelectron spectroscopic data, the redox-active ligands exist in different oxidation states due to the redox process proceeding “at ligand.” It is shown that the transition from the neutral to oxidized semiquinone form (from [Pd(LMe)2]·2Cl·H2O to [Pd\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\left( {{\text{L}}_{{{\text{Ph}}}}^{{{\text{ISQ}}}}} \right)$$\end{document}2]) occurs in the ligand and involves no palladium ions, and the oxidation state of palladium remains unchanged: Pd(II). A significant difference in the photoelectron spectroscopic characteristics obtained for the oxidized trans-complex at 298 and 153 K indicates a specific electronic lability of this complex.