Epoxidation of olefins using a dichlorodioxomolybdenum(VI)-pyridylimine complex as catalyst

TY - JOUR

T1 - Epoxidation of olefins using a dichlorodioxomolybdenum(VI)-pyridylimine complex as catalyst

AU - Balula, Salete S.

AU - Bruno, Sofia M.

AU - Gomes, Ana C.

AU - Valente, Anabela A.

AU - Pillinger, Martyn

AU - Gonalves, Isabel S.

AU - MacQuarrie, Duncan J.

AU - Clark, James H.

PY - 2012/5/30

Y1 - 2012/5/30

N2 - 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 MoO 2Cl 2(L 1) (L 1 = pyim (1), pyim-MTS) were then prepared by treatment of the organic ligand or ligand-silica with the solvent adduct MoO 2Cl 2(THF) 2. MoO 2Cl 2(pyim) (1) is a highly active catalyst for the epoxidation of olefins (cyclooctene (Cy), cyclododecene, 1-octene, trans-2-octene, R-(+)-limonene) at 55 °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.

AB - 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 MoO 2Cl 2(L 1) (L 1 = pyim (1), pyim-MTS) were then prepared by treatment of the organic ligand or ligand-silica with the solvent adduct MoO 2Cl 2(THF) 2. MoO 2Cl 2(pyim) (1) is a highly active catalyst for the epoxidation of olefins (cyclooctene (Cy), cyclododecene, 1-octene, trans-2-octene, R-(+)-limonene) at 55 °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.

KW - Catalysis

KW - Dioxomolybdenum(VI) complex

KW - Ionic liquids

KW - Olefin epoxidation

KW - Pyridylimine ligand

KW - Silica supports

UR - http://www.scopus.com/inward/record.url?scp=84860314328&partnerID=8YFLogxK

U2 - 10.1016/j.ica.2012.01.029

DO - 10.1016/j.ica.2012.01.029

M3 - Article

AN - SCOPUS:84860314328

SN - 0020-1693

VL - 387

SP - 234

EP - 239

JO - INORGANICA CHIMICA ACTA

JF - INORGANICA CHIMICA ACTA

ER -