New asymmetric (salen)MnIII and UO2 complexes containing a calixarene unit in the ligand framework were synthesized. The UO2 complexes were characterized by 1H-, 13C-, 2D TOCSY and T-ROESY NMR spectroscopy. Furthermore, the structure of one UO2 complex was determined by singlecrystal X-ray analysis. The data showed that UO2 complexes, which can be considered in first approximation models of the Mn=O oxidant active species, possess a chiral pocket and adopt relevant conformations for the selectivity of the oxygen transfer process. Epoxidation data of model alkenes with the MnIII complexes showed moderate ee values and were not conclusive in indicating that the calixarene unit might be able to influence the selectivity by a molecular recognition mechanism.
|Titolo:||Novel Chiral Mn(III)-Salen Complexes Containing a Calix-Arene Unit as Enantioselective Epoxidation Catalysts|
|Data di pubblicazione:||2005|
|Appare nelle tipologie:||1.1 Articolo in rivista|