abstract
The complexes [MoO(2)Cl(HC(bim)(3))]Y (Y = Cl (1), BF(4) (2) and PF(6) (3)) have been prepared by reaction of MoO(2)Cl(2)(THF)(2) (for 1) or [MoO(2)Cl(THF)(3)]Y (for 2 and 3) with the tridentate ligand HC(bim)(3) = tris(benzimidazolyl)methane, and characterized by IR and Raman spectroscopy, and (1)H NMR. The turnover frequencies for the epoxidation of cis-cyclooctene at 55 degrees C with tert-butyl hydroperoxide (TBHP, in decane) as the oxidant and complexes 1-3 as catalysts are in the range of 70-200 mol mol(Mo)(-1) h(-1). 1,2-Epoxycyclooctane is always the only reaction product for reaction times up to 24 h. With the aim of facilitating the recyclability of the complexes, the ionic liquids (ILs) [BMIM]Y and [BMPy]Y(BMIM = 1-n-butyl-3-methylimidazolium,BMPy = 1-n-butyl-3-methylpyridinium:Y = BF(4) or PF(6)) were applied as ionic solvents. The catalytic performance for cyclooctene epoxidation depends strongly on the catalyst solubility in the IL. Of the 12 catalyst/IL mixtures examined, the systems 1/[BMIM]PF(6) and 1/[BMPy]PF(6) exhibit the most favorable reaction rates allied with good recyclability. The 1/[BMIM]PF(6) system was further applied using different oxidants (aqueous TBHP, aqueous H(2)O(2) and urea-hydrogen peroxide adduct) and olefins (norbornene, cyclohexene, styrene, alpha-pinene). (C) 2009 Elsevier B.V. All rights reserved.
keywords
ALPHA-PINENE OXIDE; DIOXOMOLYBDENUM(VI) COMPLEXES; CRYSTAL-STRUCTURES; ORGANOMOLYBDENUM(VI) OXIDES; LIGAND; CYCLOOCTENE; BEARING; REACTIVITY; ORGANORHENIUM(VII); REARRANGEMENT
subject category
Chemistry; Environmental Sciences & Ecology
authors
Gago, S; Balula, SS; Figueiredo, S; Lopes, AD; Valente, AA; Pillinger, M; Goncalves, IS
our authors
Anabela Tavares Aguiar Valente
Principal Researcher
Isabel Maria de Sousa Gonçalves
Associate Professor
Martyn Pillinger
Principal Researcheracknowledgements
We are grateful to the Fundacao para a Ciencia e a Tecnologia (FCT, Portugal), POCI 2010, OE and FEDER for funding through the project PTDC/QUI/71198/2006. SG, SSB and SF thank the FCT for grants. M.M. Marques is acknowledged for the elemental analysis data.