Mechanism of Olefin Epoxidation by Transition Metal Peroxo Compounds

Abstract

Density functional calculations on model systems show that olefin epoxidation by peroxo complexes of early transition metals (Mo, W, Re) in general proceeds by direct transfer via spiro-type transition structures, rather than via insertion. Oxygen transfer by hydroperoxo complexes is at least competitive, if not preferred for Mo, while it is clearly preferred for Ti. A simple MO analysis allows to rationalize many trends (e.g. effects of the metal center and of additional base ligands) found for the computational results.