Heterogeneous oxidation catalysts formed in situ from molybdenum tetracarbonyl complexes and tert-butyl hydroperoxide

abstract

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.

keywords

OLEFIN EPOXIDATION CATALYSTS; MONOXIDE-RELEASING MOLECULE; CARBON-MONOXIDE; CRYSTAL-STRUCTURES; MILD OXIDATION; PRECURSORS; SULFOXIDES; DERIVATIVES; SULFIDES; LIGAND

subject category

Chemistry; Environmental Sciences & Ecology

authors

Neves, P; Amarante, TR; Gomes, AC; Coelho, AC; Gago, S; Pillinger, M; Goncalves, IS; Silva, CM; Valente, AA

our authors

acknowledgements

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

Share this project:

Related Publications

We use cookies for marketing activities and to offer you a better experience. By clicking “Accept Cookies” you agree with our cookie policy. Read about how we use cookies by clicking "Privacy and Cookie Policy".