This paper reports recent findings on nanostructured mixed metal clusters of nickel and molybdenum on the surface of chabazite (CHA) which show novel activity and resistance to sulfur poisoning in hydrogenation catalysis. Three systems, Ni-CHA, Mo-CHA, and NiMo-CHA, were prepared by ion-exchange and characterized by instrumental neutron activation analysis (INAA), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), X-ray diffraction (XRD) and NH3 temperature programmed desorption (TPD) in order to give insight into the structure of the supported phases. Ethylene hydrogenation was used as a probe reaction, in both the presence and absence of H2S, as a measure of the activity. selectivity and deactivation characteristics of these systems. The findings of the characterization studies support the observed catalytic properties of bimetallic NiMo-CHA, which shows unique selectivity and resistance to sulfur poisoning relative to the monosmetallic (Ni-CHA and Mo-CHA) systems. These findings indicate a synergistic effect between nickel and molybdenum on chabazite. (c) 2007 Elsevier B.V. All rights reserved.