ZEOLITE-ENCAPSULATED MANGANESE(III)SALEN COMPLEXES

Manganese(III) complexes of [N,N'-ethylenebis(salicylidene-aminato)] ( salen), [N, N'-ethylenebis(5-chloro-salicylidene aminato)] (Cl-2 Salen ), [N, N'-ethylenebis(5-bromo-salicylidene-aminato)] (Br-2 Salen) and [N, N'-ethylenebis(5-nitro-salicylidene-aminato)] [(NO2)(2)Salen] have been encapsulated in the supercages of zeolite X by the zeolite synth esis method. The catalysts have been characterized by FTIR, UV-Vis and EPR spectroscopic techniques, XRD, SEM, thermal and elemental analysi s, as well as nitrogen adsorption and cyclic voltammetric studies. The extent of encapsulation of the Mn(III)Salen complexes in zeolite X va ries with the nature of the substituent group on the aromatic ring. Wh ile bromo groups enhance encapsulation, substitution with -NO2, groups decreases the amounts of Mn(III) complexes encapsulated in the caviti es of the zeolites. Cyclic voltammetric data indicate that the zeolite matrix facilitates the reduction of Mn(III) to Mn(ll), suggesting tha t it behaves like an electron-withdrawing substituent. The aerobic oxi dation of styrene to benzaldehyde, styrene oxide and phenylacetaldehyd e over these catalysts is also reported. (C) 1998 Elsevier Science B.V . All rights reserved.