Epoxidation of olefins using a dichlorodioxomolybdenum(VI)-pyridylimine complex as catalyst
authors Balula, SS; Bruno, SM; Gomes, AC; Valente, AA; Pillinger, M; Goncalves, IS; Macquarrie, DJ; Clark, JH
nationality International
journal INORGANICA CHIMICA ACTA
author keywords Dioxomolybdenum(VI) complex; Pyridylimine ligand; Catalysis; Olefin epoxidation; Silica supports; Ionic liquids
keywords SUPPORTED PALLADIUM CATALYST; ORDERED MESOPOROUS SILICA; TERT-BUTYL HYDROPEROXIDE; BIDENTATE LEWIS-BASE; DIOXOMOLYBDENUM(VI)-BIPYRIDINE COMPLEXES; CYCLOOCTENE EPOXIDATION; MOLYBDENUM COMPLEXES; LIGANDS; PERFORMANCE; PRECURSORS
abstract The ligand N-(n-propyl)-2-pyridylmethanimine (pyim) and an immobilized analogue of this ligand (pyim-MTS) were prepared by the condensation reaction of 2-pyridinecarboxaldehyde with either n-propylamine or 3-aminopropyl groups covalently attached to a micelle-templated silica (MTS). Free and immobilized dioxomolybdenum(VI) complexes of the type MoO2Cl2(L-1) (L-1 = pyim (1), pyim-MTS) were then prepared by treatment of the organic ligand or ligand-silica with the solvent adduct MoO2Cl2(THF)(2). MoO2Cl2(pyim) (1) is a highly active catalyst for the epoxidation of olefins (cyclooctene (Cy), cyclododecene, 1-octene, trans-2-octene, R-(+)-limonene) at 55 degrees C using tert-butylhydroperoxide (TBHP) as the oxidant under solvent-free conditions, giving the corresponding epoxides as the only reaction products. A turnover frequency of 1855 mol mol(Mo)(-1) h(-1) was measured for the epoxidation of Cy, and the epoxide (CyO) was formed quantitatively within 4.5 h. The MTS-supported complex was less active, and exhibited temperature-dependent leaching of active species. As an alternative approach to facilitating catalyst recycling, complex 1 was investigated with the ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate as solvent. The 1/IL phase could be reused, giving ca. 95% CyO yield in each run. (C) 2012 Elsevier B.V. All rights reserved.
publisher ELSEVIER SCIENCE SA
issn 0020-1693
year published 2012
volume 387
beginning page 234
ending page 239
digital object identifier (doi) 10.1016/j.ica.2012.01.029
web of science category Chemistry, Inorganic & Nuclear
subject category Chemistry
unique article identifier WOS:000303325800031
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