Molybdenum(VI) oxides bearing 1,4,7-triazacyclononane and 1,1,1-tris(aminomethyl)ethane ligands: Synthesis and catalytic applications
authors Petrovski, Z; Valente, AA; Pillinger, M; Dias, AS; Rodrigues, SS; Romao, CC; Goncalves, IS
nationality International
journal JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL
author keywords molybdenum(VI) complexes; nitrogen ligands; olefin epoxidation; tert-butyl hydroperoxide; oxidative decarbonylation
keywords OLEFIN EPOXIDATION; DIOXOMOLYBDENUM(VI) COMPLEXES; CRYSTAL-STRUCTURE; ORGANOMOLYBDENUM(VI) OXIDES; ALKENE EPOXIDATION; IONIC LIQUIDS; LEWIS-BASE; OXIDATION; ORGANORHENIUM(VII); TUNGSTEN
abstract A series of ionic dioxomolybdenum(VI) complexes of general formula [MoO(2)Cl(L)]Y containing tridentate nitrogen ligands [L = 1,4,7-triazacyclononane(tacn), 1,1,1-tris(methylaminomethyl)ethane (Me(3)-tame) and N,N',N"-tribenzyl-1,1,1-tris(methylaminomethyl)ethane (Bn(3)Me(3)-tame); Y=Cl, BF(4)(-)] were prepared by replacement of the solvent molecules and one of the chloride ligands in the adducts MoO(2)Cl(2)(solv)(2) (solv = THF, DMF). The complexes were examined as catalysts for the epoxidation of cyclooctene at 55 degrees C, using tert-butyl hydroperoxide (t-BuOOH) as the oxidant. The kinetic profiles and initial activities (60-100 mol mol(Mo)(-1) h(-1)) were comparable with those usually exhibited by MoO(2)Cl(2)L complexes bearing bidentate heterocyclic amines. The tricarbonyl complexes (Me(3)-tame)M(CO)(3) (M=Mo, Cr) were also prepared and used directly as catalyst precursors for the epoxidation of cyclooctene using t-BuOOH. Induction periods were observed due to relatively slow oxidative decarbonylation and formation of the active oxidising species. When the Mo tricarbonyl complex was used, 1,2-epoxycyclooctane was the only product, while with the Cr complex a significant amount of 1,2-cyclooctanediol was formed due to the enhanced Lewis acidity of the active catalyst. The Mo complexes containing the tame ligands were further studied as catalysts or catalyst precursors for the epoxidation of cyclododecene, 1-octene, trans-2-octene, (R)-(+)-limonene and alpha-pinene. (c) 2006 Elsevier B.V. All rights reserved.
publisher ELSEVIER SCIENCE BV
issn 1381-1169
year published 2006
volume 249
issue 1-2
beginning page 166
ending page 171
digital object identifier (doi) 10.1016/j.molcata.2006.01.014
web of science category Chemistry, Physical
subject category Chemistry
unique article identifier WOS:000237173500023
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