Structural, spectral, electrochemical and catalytic reactivity studies of a series of N2O2 chelated palladium(II) complexes

A series of neutral salicylaldiminato Pd(II) complexes have been synthesized and characterized. Spectral and electrochemical properties of the complexes in the solution phase have been investigated. The structure of complex 9 has been confirmed by X-ray analysis. Spectroscopic characteristics were determined by visible absorption spectra. Cyclic voltammetry analysis has been performed to determine the energy levels of the compounds. The coordination of the Schiff base, according to the spectroscopic techniques, appears to occur through the two azomethine nitrogens and two o-OH groups. The salen type Pd(II) complexes have been used as catalysts for the formation of cyclic organic carbonates from carbon dioxide and liquid epoxides, which served as both reactant and solvent. The more electron donating substituents on the backbone and the aryl ring of the ligand system, in particular, effectively promote carbon dioxide activation with liquid epoxides under homogeneous conditions. (C) 2012 Elsevier Ltd. All rights reserved.