Oxidation of phenol with H2O2 catalysed by Cu(II), Ni(II) and Zn(II) complexes of N,N′-bis-(salicylidene)diethylenetriamine (H2saldien) encapsulated in Y-zeolite

Interaction of excess of N,N'-bis(salicylidene)diethylenetriamine (H(2)saldien) with Cu(II), Ni(II) and Zn(H) exchanged zeolite-Y at ca. 90 degreesC leads to the encapsulation of ligand in the super cages of zeolite followed by complexation with metal ions. These encapsulated metal complexes have been characterised by IR and UV-Vis spectroscopic studies and thermal as well as X-ray diffraction (XRD) patterns. All encapsulated complexes serve as catalyst for the decomposition of H2O2 and for the oxidation of phenol to a mixture of catechol and hydroquinone using H2O2 as an oxidant. A suitable reaction condition has been optimised for [Zn(saldien)]-Y by considering the effect of various parameters such as different solvents, concentration of substrate, reaction time and amount of oxidant etc. for the maximum transformation of phenol. Thus, for a fixed amount of catalyst (0.025g), 5.67g of 30% H2O2 in 2 ml MeCN were sufficient enough to catalyse the oxidation of 4.70 g of phenol at 80 degreesC to give maximum transformation of phenol. Under the same reaction conditions the catalytic activity of these complexes follow the order: [Zn(saldien)]-Y (53%) > [Ni(saldien)]-Y (51%) > [Cu(saldien)]-Y (45%) after 24h of reaction time. These catalytic activities were always found better over their respective non-encapsulated complexes. (C) 2003 Elsevier Science B.V. All rights reserved.