Importantly, compared to our previous work , here the total reaction time for the highest concentration of Mg-Ti butoxide catalyst was markedly shorter, as compared to homometallic bismuth and zinc catalysts (7 hours and 25 hours, respectively)-despite a lower catalyst concentration (1 mol% vs. 2 mol%). This confirms that a different catalytic mechanism was involved for the case of the heterometallic Mg-Ti butoxide catalyst system. In the previous work , the homometallic catalysts were acting via either insertion mechanism or as Lewis acids . Meanwhile, in the heterometallic system used here, the catalyst can act simultaneously in both ways, which can significantly influence the reaction kinetics.