Functional models for rhodium-mediated olefin-oxygenation catalysis.

Oxygenation of C-H and C=C bonds of hydrocarbons with H2O2 and O2 is an important industrial method to convert mineral oil into useful chemicals. Despite their enormous economic impact, these reactions are still not fully understood. In the early 1970s, the potential of Rh and Ir complexes for olefin oxygenation was investigated intensively. Simple inorganic salts of these metals proved to be rather useless for industrial application when compared with the traditional Wacker system. However, the appropriate choice of ligands allows the stepwise oxidation of olefins at Rh and Ir. These systems are therefore useful to study mechanistic details of substrate binding and C-O bond formation at the catalytic metal center. Insight from these model studies helps in understanding the catalytic reactions at these (and possibly other) metal centers. Further insight into the differences between the Rh system and traditional Wacker-type oxidation at Pd may lead to useful applications.