In this work we suggest that certain structures present in real commercial catalysts maybe related to low dimensional structures and present a theoretical study of two MoS2 clusters (one made of 61 atoms and the second one made of 68 atoms). The 61 atoms cluster has 7 sulfur atoms decorating at the top of sulfur (S) layer in order to analyze the effects produced on the electronic properties. The first cluster yielded semiconductor behavior with a forbidden energy gap E-g of the order of 0.11 eV, while the second cluster decorated with seven S atoms yielded metallic behavior. A careful analysis to the partial density of states (PDOS) indicate that the contributions to the total DOS in the vicinity of the Fermi level, from the seven S atoms located at the surface is negligible, they serve only as promoters to the metallic behavior to the system.