ESR study of MoY and PdMoY reduction

This paper deals with the reduction of MoY and PdMoY using ESR in order to study the effect of molybdenum on the reducibility of palladium ions. The evolution of signals of paramagnetic species of palladium (Pd3+ in 4d7 and Pd+ in 4d9) and molybdenum (Mo5+ in 4d1) was followed by EPR spectroscopy. Two paramagnetic species of Mo5+ were observed after reduction under hydrogen, the first with g// = 1.87 and the second with g// = 1.89. However, the Mo5+ ion on the zeolite exhibited various coordination symmetries upon reduction or other treatments, depending on the preparation method. The analysis of the g tensors allowed these signals to be attributed to molybdenyl ions in penta- and hexacoordination symmetries. Copyright © 2004 John Wiley & Sons, Ltd.