General catalysis procedure: Stock solutions of catalyst (0.012 M) and diphenylacetylene (0.1 M) in deuterated toluene were prepared in the glovebox. In a vial, 0.25 mL of catalyst solution and 0.3 mL of diphenylacetylene solution were added turning the solution red. With a microsyringe, 4.2 µL of mesitylene were added to the solution and mixed. The reaction mixture was transferred to a J-Young NMR tube. The tube was connected to a gas setup and degassed by two freezepump-thaw cycles and with the solution inside of a Dewar with liquid nitrogen, hydrogen gas was introduced. The solution was warmed up at room temperature and analyzed and placed in an oil bath at 70 ºC. The concentrations of products were determined by 1 H NMR using mesitylene as internal standard. Proton peaks used in quantification (d 8 -tol, 400 MHz): 44 Diphenylacetylene: 7.46 (m, 4H) (E)-stilbene: 7.29 (dd, J= 8.3, 1.3 Hz, 4H) (Z)-stilbene: 6.44 (s, 2H) 1,2-diphenylethane: 2.72 (s, 1H) Mesitylene: 6.67 (s, 3H) Mercury drop experiment procedure: Two Schlenk bombs with stirring bars (one containing a drop of mercury) were charged with 0.25 mL of stock solution (0.012 M) of catalyst and 0.6 mL of stock solution of diphenylacetylene (0.1 M) in toluene (total volume 0.85 mL). With a microsyringe, 4.2 µL of mesitylene were added to the solution and mixed. Both Schlenks were connected to a gas setup, degassed twice by freeze-pump procedure and H2 was introduced. Both Schlenk bombs were heated under intense stirring for 5 hours at 70 ºC. After this time, the pressure was released. 0.0062 mmol of dodecane, 5 mL of Et2O and 1 mL of water were added. The organic phase was extracted, and 1 mL of acetone was added to dilute the mixture. The solution was analyzed by GC-FID and no difference was found in the product concentration.