Utilize este identificador para referenciar este registo: http://hdl.handle.net/10400.1/3224
Título: Dichloro and dimethyl dioxomolybdenum(VI)–diazabutadiene complexes as catalysts for the epoxidation of olefins
Autor: Moreira, José A.
Valente, Anabela A.
Pillinger, Martyn
Nunes, Carla D.
Gonçalves, Isabel S.
Lopes, André D.
Romão, Carlos C.
Kuhn, Fritz E.
Data: 2004
Editora: RSC Publishing - Royal Society of Chemistry
Citação: Moreira, José A.; Valente, Anabela A.; Pillinger, Martyn; Nunes, Carla D.; Gonçalves, Isabel S.; Lopes, André D.; Romão, Carlos C.; Kuhn, Fritz E.Dichloro and dimethyl dioxomolybdenum(VI)–diazabutadiene complexes as catalysts for the epoxidation of olefins, New Journal of Chemistry, 2004, 28, 308-313, 2004.
Resumo: The dioxomolybdenum(VI) complex [MoO2Cl2{p-tolyl(CH3DAB)}] has been prepared in good yield by reaction of the solvent adduct MoO2Cl2(THF)2 with one equivalent of the bidentate ligand N,N-p-tolyl-2,3-dimethyl- 1,4-diazabutadiene. Treatment of the dichloro complex with the Grignard reagent CH3MgCl gives the dimethyl derivative [MoO2(CH3)2{p-tolyl(CH3DAB)}]. The complexes are highly active and selective catalysts for the homogeneous epoxidation of cyclooctene using tert-butyl hydroperoxide (TBHP) as the oxidant. In both cases, the initial activity is ca. 175 mol mol 1 Mo h 1 and cyclooctene oxide is obtained quantitatively within 4 h. It was possible to recover the dimethyl complex at the end of the reaction and reuse it in a second run with only a small decrease in activity. The complexes are also active and selective for the epoxidation of other olefins, such as 1-octene, 2-octene, cyclododecene and (R)-(þ)-limonene, with TBHP. The catalytic production of cyclooctene oxide was investigated in detail, varying either the reaction temperature or the initial concentrations of substrate, oxidant and catalyst precursor. Kinetic studies show that the catalyst precursor–oxygen donor complex formation is first-order in TBHP and in the metal complex [MoO2Cl2{p-tolyl(CH3DAB)}]. A specific rate of 3.2 mol 1 dm3 s 1 was found for catalyst formation at 25 C. Activation parameters for this reaction have also been measured (DH6¼ ¼ 48 3 kJ mol 1, DS6¼ ¼ 112 10 J mol 1 K 1).
Peer review: yes
URI: http://hdl.handle.net/10400.1/3224
DOI: http://dx.doi.org/10.1039/B311114H
ISSN: 1144-0546
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