resumo
The tetracarbonyl complexes cis-[Mo(CO)(4){2-13(5)-pyrazolyl]pyridine}] (1) and cis-[Mo(CO)(4){ethyl[3-(2-pyridyl)-1-pyrazolyllacetate}] (2) were obtained in excellent yields by microwave-assisted heating of a mixture of Mo(CO)(6) and the organic ligand in toluene at 110 degrees C for 30 min. Complexes 1 and 2 are air stable, storable catalyst precursors for the epoxidation of olefins by tert-butyl hydroperoxide (TBHP). In situ oxidative decarbonylation of 1 gives the tetranuclear compound [Mo(4)O(12){2-[3(5)-pyrazolyl]pyridine}(4)] (3). Elemental analysis and infrared data indicate that the oxidation of 2 gives an octameric species with the molecular formula [Mo(8)O(24){ethyl[3-(2-pyridyl)-1-pyrazolyl]acetate}(4)] (4). The molybdenum oxide/pyrazolylpyridine compounds 3 and 4, which can be readily prepared in very good yields from the parent carbonyls upon reaction with TBHP in n-decane/CH(2)Cl(2) at room temperature, are active and stable heterogeneous catalysts for the epoxidation of cis-cyclooctene (Cy) by TBHP, giving 1,2-epoxycyclooctane as the only product. The highest activity is found for 4: ca. 90% epoxide yield after 6h reaction at 55 degrees C. Further experiments confirmed that 2 is an effective catalyst precursor for (i) the epoxidation of Cy by aqueous TBHP, giving the corresponding epoxide as the only product, (ii) the selective epoxidation of R-(+)-limonene by TBHP (in n-decane), and (iii) the selective oxidation of methyl phenyl sulfide to the corresponding sulfoxide by aqueous TBHP or H(2)O(2) at 35 degrees C. (c) 2011 Elsevier B.V. All rights reserved.
palavras-chave
OLEFIN EPOXIDATION CATALYSTS; MONOXIDE-RELEASING MOLECULE; CARBON-MONOXIDE; CRYSTAL-STRUCTURES; MILD OXIDATION; PRECURSORS; SULFOXIDES; DERIVATIVES; SULFIDES; LIGAND
categoria
Chemistry; Environmental Sciences & Ecology
autores
Neves, P; Amarante, TR; Gomes, AC; Coelho, AC; Gago, S; Pillinger, M; Goncalves, IS; Silva, CM; Valente, AA
nossos autores
Ana Catarina Costa Gomes Alves
Investigador Auxiliar
Anabela Tavares Aguiar Valente
Investigador Principal
Carlos Manuel Silva
Professor associado
Isabel Maria de Sousa Gonçalves
Professor associado
Martyn Pillinger
Investigador Principal
Patrícia dos Santos Neves
Investigador Auxiliaragradecimentos
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. CICECO is acknowledged for financial support (including a post-doctoral research grant to ACG) through the project entitled