MOLYBDENUM-CATALYZED OLEFIN EPOXIDATION - LIGAND EFFECTS

We synthesized substituted pyrazolylpyridine ligands to examine their donor properties by spectroscopic (IR, NMR) and computational (AM1) me thods. Tile influence of the substitution patterns on spectroscopic an d thermodynamic Features of molybdenum oxobisperoxo complexes [(L-L)Mo O(O-2)(2)] (L-L = 2-(1-alkyl-3-pyrazolyl)pyridine/pyrazine) correlates with the activities of the complexes in catalytic olefin epoxidation reactions. This further proof for the relation between the Lewis acidi ty and the catalytic activity of epoxidation catalysts supports a reac tion mechanism in which the peroxo complex activates the oxidizing age nt (H2O2, ROOH) instead of directly transferring an oxygen atom from a eta(2)-peroxo ligand to the olefin.