Microwave-assisted molybdenum-catalysed epoxidation of olefins
authors Abrantes, M; Neves, P; Antunes, MM; Gago, S; Paz, FAA; Rodrigues, AE; Pillinger, M; Goncalves, IS; Silva, CM; Valente, AA
nationality International
journal JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL
author keywords Molybdenum; Cyclopentadienyl ligands; Carbonyl ligands; Microwave; Epoxidation
keywords CAMBRIDGE STRUCTURAL DATABASE; MAIN-GROUP ELEMENTS; HYDROGEN-PEROXIDE; ORGANIC-SYNTHESIS; IONIC LIQUIDS; TRICARBONYL COMPLEX; CARBONYL-COMPLEXES; CRYSTAL-STRUCTURES; TRANSITION-METALS; INDENYL LIGANDS
abstract The performance of CpMo(CO)(3)CH(3) as a catalyst precursor in the epoxidation of cis-cyclooctene and R-(+)-limonene with tert-butylhydroperoxide (TBHP), at 55 degrees C, was investigated for the first time using microwave (MW)-assisted heating, and the results were compared with those obtained using conventional heating with a thermostated oil bath (OB). The reactions were carried out under monophasic (no co-solvent, or with 1,2-dichloroethane, toluene, hexane) or biphasic liquid-liquid (using the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate, [BMIM][BF(4)]) conditions. The heating methods did not affect product selectivity: 100% to cyclooctene oxide, and 93% to limonene oxide (66-72% diastereomeric excess, trans-1,2-(+)-limonene oxide) at 80% limonene conversion. However, the initial reaction rates strongly depend on the applied heating method. The favourable MW effect is essentially due to the faster heating up of the reaction mixture increasing the overall epoxidation rate in the early stage of the heating process, which is supported experimentally by a comparison of (i) the measured temperature vs time curves, (ii) the kinetic data for the MW method with that for the OB method where the reagents and reactor walls are pre-heated (OB-preH method), and (iii) the estimated apparent activation energies and pre-exponential factors for the two olefins using the MW, OB, and OB-preH methods. The crystal structure of the molybdenum tricarbonyl catalyst precursor was unveiled from single-crystal X-ray diffraction studies at 150K. The complex crystallises as a racemic twin in the monoclinic P2(1) space group. (c) 2010 Elsevier B.V. All rights reserved.
publisher ELSEVIER SCIENCE BV
issn 1381-1169
year published 2010
volume 320
issue 1-2
beginning page 19
ending page 26
digital object identifier (doi) 10.1016/j.molcata.2009.12.011
web of science category Chemistry, Physical
subject category Chemistry
unique article identifier WOS:000276011600003

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