| Abstract: | Methyltrioxorhenium(VII) has found numerous applications in various catalytic processes. In olefin epoxidation its activity can be enhanced by the addition of aromatic Lewis base nitrogen donor ligands, e.g. pyridines and pyrazoles. Due to the comparatively weak coordination of these ligands, a significant excess has to be used. Therefore the MTO/chiral Lewis base/H2O2 system is not very useful for chiral epoxidations. In contrast to this, dimethyldioxomolybdenum(VI) MoO2(CH3)2 undergoes a significantly stronger interaction with Lewis bases and seems, despite its generally somewhat lower activity, a reasonable candidate for application in chiral epoxidation reactions together with an appropriate chiral Lewis base ligand. Complexes of the type MoO2(CH3)2L are accessible via MoO2X2L (X = Cl, Br). These latter compounds are even more active in olefin epoxidation than MoO2(CH3)2L. Unfortunately, however, all the Mo(VI) complexes mentioned above need t‐butyl hydroperoxide as oxidizing agent and do not show activity in the presence of H2O2. |
