The static and dynamical properties of graphene, silicene and their fully hydrogenated compounds were studied using a semi-empirical potential of the form proposed by Tersoff with the addition of a torsion-like term. The importance of the torsion term for bi-dimensional silicon compounds is analyzed. Calculated structures are in reasonable agreement with experiments or first principle calculations predicting a flat structure for graphene and a buckled one for silicene, silicane and graphane.