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

authors	Neves, P; Amarante, TR; Gomes, AC; Coelho, AC; Gago, S; Pillinger, M; Goncalves, IS; Silva, CM; Valente, AA
nationality	International
journal	APPLIED CATALYSIS A-GENERAL
author keywords	Molybdenum; Heterogeneous catalysis; Pyrazolylpyridine ligands; Oxidative decarbonylation; Epoxidation; Sulfoxidation
keywords	OLEFIN EPOXIDATION CATALYSTS; MONOXIDE-RELEASING MOLECULE; CARBON-MONOXIDE; CRYSTAL-STRUCTURES; MILD OXIDATION; PRECURSORS; SULFOXIDES; DERIVATIVES; SULFIDES; LIGAND
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.
publisher	ELSEVIER SCIENCE BV
issn	0926-860X
year published	2011
volume	395
issue	1-2
beginning page	71
ending page	77
digital object identifier (doi)	10.1016/j.apcata.2011.01.029
web of science category	Chemistry, Physical; Environmental Sciences
subject category	Chemistry; Environmental Sciences & Ecology
unique article identifier	WOS:000288925400010