A palladium(II) 4-hydroxysalicylidene Schiff-base complex anchored on functionalized MCM-41: An efficient heterogeneous catalyst for the epoxidation of olefins

Synthetic procedures are described for anchoring of N-(3-(trimethoxysilyl)-propylethylenediamine on the surface of the mesoporous silica, MCM-41 (MCM-41-N). The condensation of 4-hydroxysalicylidene with MCM-41-N creates the new MCM-41-N-Hdhba Schiff-base. The synthesis and characterization of the new palladium (II) complex, [Pd(MCM-41-N-(Hdhba)2(dhba)Cl(H2O)], is also described. The structure and morphology of the Schiff-base and the Pd(II) complex have been examined using spectroscopic (IR, Raman, XPS, UV–vis and solid state 13C and 90Si NMR), morphological (low angle XRD, and HRTEM-EDS), elemental analysis, N2 physisorption and thermal measurements. The heterogeneous catalytic epoxidations of n-octene, cyclooctene and styrene were achieved by employing the new Pd(II) complex as a catalyst in the presence of aqueous 30% H2O2–0.2 M NaHCO3 at atmospheric pressure and 353 K. The influence of pH, temperature, time and amount of catalyst has also been investigated. The catalyst can be readily separated from the epoxidation reactions mixtures and can be recovered after several catalytic cycles.