Synthesis and full characterization of molybdenum and antimony corroles and utilization of the latter complexes as very efficient catalysts for highly selective aerobic oxygenation reactions

Two molybdenum and three antimony corroies were isolated and characterized by NMR, EPR, and electrochemistry. The very negative reduction potentials of the (oxo)molybdenum(V) corroies are clearly related to their inactivity as oxygen transfer reagents and the unsuccessful attempts to isolate lower-valent molybdenum corroies. X-ray crystallography of the (oxo)molybdenum(V) corroie 1a and the trans-difluoroantimony(V) corroie 2c, the first of their kind, revealed that their molecular structures represent extreme cases of such complexes: a highly domed corrole with very large out-of-plane metal displacement for 1a (0.73 Å) and a very flat corroie with the metal ion in its center for 2c. All three antimony corroies displayed high activity and selectivity as catalysts for the photoinduced oxidation of thioanisole by molecular oxygen, with superior results obtained in alcoholic solvents with 2c as catalyst. Allylic and tertiary benzylic CH bonds were also oxidized under those conditions, with absolute selectivity to the corresponding hydroperoxides.