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

• Published in: Applied catalysis. A, General General, 2014-11, Vol.488, p.148-159
• Main Authors: Hassan, Hassan M.A., Saad, Eman M., Soltan, Mohamed S., Betiha, Mohamed A., Butler, Ian S., Mostafa, Sahar I.
• Format: Article
• Language: English
• Subjects: Catalysis; Catalysts; Chemistry; Colloidal state and disperse state; Complex; Epoxidation; Exact sciences and technology; General and physical chemistry; MCM-41; Olefins; Palladium; Porous materials; Schiff-base; Styrenes; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Thermal measurements; X-ray photoelectron spectroscopy
• ISSN: 0926-860X; 1873-3875
• DOI: 10.1016/j.apcata.2014.09.040

Schematic representation of functionalized MCM-41 with N-(3-(trimethoxysilyl)propyl)ethylenediamine (MCM-41-N), Schiff-base (MCM-41-N-Hdhba) and [Pd(MCM-41-N-(Hdhba)2-(dhba)Cl(H2O)] within the pore channels of MCM-41. •N-(3-(trimethoxysilyl)propylethylenediamine is anchored onto MCM-41 (MCM-41-N).•Condensation of 4-hydroxysalicylidene creates MCM-41-N-Hdhba Schiff-base.•Pd(II) complex of MCM-41-N-Hdhba is reported.•Catalytic epoxidation of olefins is achieved by Pd(II) complex.•Recovery of Pd(II) catalyst after several cycles is discussed. 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% H2O2–0.2M NaHCO3 at atmospheric pressure and 353K. 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.