The studies on the adsorption and dehydrogenation reactions of ethane and ethylene on the Pt 4 Ge x (x = 0-4) clusters show that Ge alloying reduces the reactivity of Pt. First, the binding energies of these adsorbates to the clusters are reduced as the Ge content increases. This trend can be correlated to the charge transfer occurring from Ge to Pt. Charge transfer processes have been used in the past to explain the reactivity modulation of other doped Pt catalysts, such as Sn, Si, or B. As can be seen in Fig. (top panel), the larger the Ge content on our catalysts, the larger the negative charge on Pt. Such a charge transfer originates from the formation of Pt-Ge bonds (Fig. middle panel), which are polarized due to the electronegativity difference between the constituent elements (Pt 2.28 vs Ge 2.01). Pt-Ge covalent bonds were shown previously to confer equimolar alloyed clusters a large stabilization, making them more inert. The reactivity of a given catalyst should be adjusted for every reaction, following the Sabatier principle. In this work we show that clusters containing similar amounts of Pt and Ge are inefficient to catalyze the ethane dehydrogenation reaction.