Manganese Porphyrin Hosts as Epoxidation Catalysts – Activity and Stability Control by Axial Ligand Effects

The catalytic performance of a cavity‐containing [(porphyrin)Mn] in the epoxidation of alkenes is described. Inside the catalyst cavity, nitrogen‐containing axial ligands can be bound to the porphyrin metal with high association constants, resulting in strong activation of the catalyst in the presence of only one equivalent of the ligand. Complexation of a sterically demanding ligand to the outside of the cavity‐containing catalyst can prevent catalyst decomposition through the formation of μ‐oxo dimers.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)