Tris(pyrazolyl)methane molybdenum tricarbonyl complexes as catalyst precursors for olefin epoxidation
authors Gomes, AC; Neves, P; Figueiredo, S; Fernandes, JA; Valente, AA; Paz, FAA; Pillinger, M; Lopes, AD; Goncalves, IS
nationality International
journal JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL
author keywords Molybdenum; Tris(pyrazolyl)methane ligands; Oxidative decarbonylation; Homogeneous catalysis; Olefin epoxidation
keywords MANGANESE CARBONYL-COMPLEXES; TERT-BUTYL HYDROPEROXIDE; TUNGSTEN COMPLEXES; COORDINATION CHEMISTRY; CYCLOALKYL MOIETIES; DIOXO COMPLEXES; BRIDGING UNITS; ANSA COMPOUNDS; LIGANDS; MONONUCLEAR
abstract The molybdenum tricarbonyl complexes [Mo(CO)(3)(HC(3,5-Me(2)pz)(3))] (1) and [Mo(CO)(3)(HC(pz)(3))] (2) (HC(3,5-Me(2)pz)(3) = tris(3,5-dimethyl-1-pyrazolyl)methane, HC(pz)(3) = tris(1-pyrazolyl)methane) were obtained in good yields by the microwave-assisted reaction of Mo(CO)(6) with the respective organic ligand. Complete oxidative decarbonylation of 1 and 2 was achieved by reaction with excess tert-butylhydroperoxide (TBHP) in 1,2-dichloroethane at 55 degrees C. For complex 1, the (mu(2)-oxo)bis[dioxomolybdenum(VI)] hexamolybdate of composition [{MoO2(HC(3,5-Me(2)pz)(3))}(2)(mu(2)-O)][Mo6O19] (3) was obtained in good yield, and its structure was determined by single crystal X-ray diffraction. The compound (4) obtained by oxidative decarbonylation of 2 was not unambiguously identified, but may be chemically analogous to 3. Compounds 1-4 were examined for the first time as homogeneous (pre)catalysts for the epoxidation of olefins with TBHP, using different types of cosolvents at 55 degrees C. During the catalytic reactions 1 and 2 transform in situ into 3 and 4, respectively, and the latter two are fairly stable catalysts. Catalytic tests and characterization studies of the recovered catalysts were carried out in an attempt to understand the kinetic differences observed between the compounds prepared in situ during the catalytic reaction and those prepared prior to the catalytic reaction, from the same precursor complex. (c) 2013 Elsevier B.V. All rights reserved.
publisher ELSEVIER SCIENCE BV
issn 1381-1169
year published 2013
volume 370
beginning page 64
ending page 74
digital object identifier (doi) 10.1016/j.molcata.2012.12.010
web of science category Chemistry, Physical
subject category Chemistry
unique article identifier WOS:000316094300010

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