The Special Thing about Mn (de)hydrogenation Catalysts

Hydrogenation and dehydrogenation catalysis mediated by molecular Mn catalysts were discovered in 2016. Despite their late discovery (in comparison, for instance, to related Fe and Co catalysts), many novel catalysts and catalytic reactions have since been reported with a strong focus on dehydrogenation catalysis. Here, we try to find reasons why Mn-based (de)hydrogenation catalysis made such an impact despite its late discovery. We compare the temperature dependence of the rates of well-defined Mn, Fe, and Co catalysts in ketone hydrogenation and alcohol dehydrogenation via the liberation of H2. The Mn catalyst showed an about 40–50 °C higher thermal stability in comparison to Fe and Co catalysts. In addition, details of the decomposition of Mn and Fe catalysts at the thermal limit are reported. While the PN5P-based Mn catalyst decomposes reversibly, the PN5P-based Fe catalyst does it irreversibly. Interestingly, all three catalysts (Mn, Fe, and Co) are active in alcohol dehydrogenation under very mild conditions, such as 60 °C, with Mn showing the highest activity at 100 °C