Ir-Pt/Al2O3 catalysts were prepared by adding Ir to Pt catalysts using two methods: successive impregnation (SI) or organometallic grafting (OG). These resulted in different structures: with the first method (SI) Pt and Ir sites were separated, whereas bimetallic Pt-Ir sites are created by the second method (OG), as demonstrated also by electron microscopy. We tested the bimetallic catalysts obtained by these two preparation methods using hydrocarbon transformation, particularly the reaction of ring opening of methylcyclopentane (MCP). The OG catalyst shows a very promising behavior in ring opening reaction of MCP. showing high activity and producing ring opening products (ROP) with high selectivities even at high conversion values. (C) 2010 Elsevier Inc. All rights reserved.