THE ORIGIN OF THE POSITIVE EFFECT OF CADMIUM ACETATE ON THE ACTION OFSUPPORTED PALLADIUM CATALYSTS

The complex chemistry of Pd(OAc)(2) and Cd(OAc)(2) in the solid state and in acetic acid solution has been studied. Triclinic crystals, spac e group P (1) over bar, of a new complex [CdPd (CH3COO)(4) . CH3COOH]( 2) were isolated from the solution, Palladium is square-planar coordin ated by acetate ligands, with metal - oxygen bond lengths of approxima tely 200 pm, and has cadmium at one of its free axial coordination sit es at a distance of 280 pm, Cadmium is coordinated by acetate ligands in a trigonal-prismatic geometry capped by palladium. UV/Vis spectrosc opy confirmed the existence of the complex in solution as well as in t he solid state. The thermal decomposition was characterised in detail by thermogravimetry coupled with mass spectrometric detection of the d ecomposition products and X-ray photoelectron spectroscopy (XPS), XPS revealed the presence of elemental Pd during thermal decomposition at 423 K. Thermal decomposition of the compound finally led to partially oxidised Pd and CdO. The application of [CdPd(CH3COO)(4). CH3COOH](2) as a precursor in the synthesis of supported Pd catalysts influenced t heir catalytic activity positively in a test reaction (the total oxida tion of ethylene), in comparison with catalysts prepared from binary p alladium acetate. Transmission electron microscopy of the used catalys ts revealed a significant improvement in Pd dispersion in the catalyst prepared from the complex, compared with the material prepared from P d acetate.