Norbornene Oxidation by Chiral Complexes Encapsulated in NaY Zeolite

Abstract

The preparation of chiral metal complexes in NaY zeolite is reported. The guests, chiral metal complexes, were entrapped in the supercages of NaY zeolite (host) by a two-step process in the liquid phase: (i) inclusion of the selected transition metal (rhodium(III) and manganese(II)) by ion-exchange in the porous structure and (ii) introduction of the chiral ligand, an d-erythrose amino derivative, namely (2R,4S,5R)-4-[(N-methylamino)methyl]-2-phenyl-1,3-dioxan-5-ol, followed by assembly of the complex inside the void space of the zeolite. Structural (FTIR and XRD), surface studies (SEM) and chemical analyses were used to characterize the new host–guest catalysts and the results indicated that chiral metal complexes were successfully encapsulated in supercages of the NaY zeolite. Catalytic studies were performed in liquid phase for norbornene oxidation using tert-butyl hydroperoxide as the oxygen source. The catalytic results were compared with styrene and cyclohexanol oxidation as model reactions. The prepared chiral catalysts exhibited catalytic activity for all oxidation reactions. The stability of the catalysts before and after reaction was confirmed by cyclic voltammetry and FTIR studies.