resumo
The ligand N-(n-propyl)-2-pyridylmethanimine (pyim) and an immobilised analogue of this ligand (MCM-41-pyim) were prepared by the condensation reaction of 2-pyridinecarboxaldehyde with either propylamine or aminopropyl groups covalently attached to the ordered mesoporous silica MCM-41. Free and immobilised tetracarbonyl complexes of the type cis-[Mo(CO)(4)(L)] (L = pyim (1), MCM-41-pyim) were then prepared by microwave-assisted heating of a mixture of Mo(CO)(6) and the organic ligand or ligand-silica in toluene at 110 degrees C for 30-45 min. The products were characterised by NMR spectroscopy ((1)H, (13)C and (29)Si, in solution and in the solid state), elemental analysis, N(2) adsorption, and FT-IR spectroscopy. When used as catalyst precursors for the epoxidation of cis-cyclooctene by tert-butylhydroperoxide at 55 degrees C (1 mol% catalyst (Mo), no additional co-solvent), 1,2-epoxy-cyclooctane was obtained as the only reaction product in quantitative yield after 5 h for 1 and 36% yield after 24 h for the supported complex. The use of the ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate as co-solvent led to lower catalytic activities (epoxide selectivity was always 100%) but allowed the catalyst/IL mixtures (homogeneous mixture for IL+1 and a biphasic solid + IL system for IL+MCM-41-pyim/Mo) to be easily recovered and reused in subsequent runs without loss of catalytic performance. (C) 2011 Elsevier B. V. All rights reserved.
palavras-chave
MICROWAVE-ASSISTED SYNTHESIS; DERIVATIZED DIIMINE LIGANDS; TEMPERATURE IONIC LIQUIDS; TERT-BUTYL HYDROPEROXIDE; NITROGEN DONOR LIGANDS; SCHIFF-BASE LIGANDS; CARBONYL-COMPLEXES; OLEFIN EPOXIDATION; CRYSTAL-STRUCTURE; METHYL-METHACRYLATE
categoria
Chemistry
autores
Gomes, AC; Bruno, SM; Gago, S; Lopes, RP; Machado, DA; Carminatti, AP; Valente, AA; Pillinger, M; Goncalves, IS
nossos autores
Ana Catarina Costa Gomes Alves
Investigador Auxiliar
Anabela Tavares Aguiar Valente
Investigador Principal
Isabel Maria de Sousa Gonçalves
Professor associado
Martyn Pillinger
Investigador Principal
Sofia M. Bruno
Investigador Auxiliaragradecimentos
We are grateful to the Fundacao para a Ciencia e a Tecnologia (FCT), the Programa Operacional Ciencia e Inovacao (POCI) 2010, Orcamento do Estado (OE), and Fundo Europeu de Desenvolvimento Regional (FEDER) for funding (Project PTDC/QUI/71198/2006). The FCT (S. G., S. M. B.) and the European Social Fund (S. M. B.) are acknowledged for post-doctoral grants to S. G. (SFRH/BPD/25269/2005) and S. M. B (SFRH/BPD/46473/2008). CICECO is acknowledged for financial support (including a post-doctoral research grant to A. C. G.) through the project entitled