Electrostatic immobilization of bis(oxazoline)-copper complexes on mesoporous crystalline materials: Cation exchange vs. incipient wetness methods

• Chiral box and azabox-copper complexes were non-covalently immobilized on Al-MCM41.
• Cation-exchange was not as efficient as observed with layered clays.
• The incipient wetness method produces more stable catalysts.
• Activity and selectivity depend on the chiral ligand and the pore size of Al-MCM41.

Chiral copper complexes with bis(oxazoline) and azabis(oxazoline) ligands have been immobilized by non-covalent interactions on mesoporous materials. The presence of negative charges achieved by the isomorphous substitution of silicon by aluminium is required to retain the complexes on the support. Cation-exchange was found to be not as efficient as observed with layered clays, and produce catalysts which lose their chiral ligand and give low enantioselectivity. A method employing incipient wetness produces more stable catalysts, whose activity varies to some extent according to the structure of the mesoporous material on which it is supported, and the nature of the chiral ligand.

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