resumo
The oxidative decarbonylation of the eta(3)-allyl dicarbonyl complexes [Mo(eta(3)-C3H5)Cl(CO)(2)(L)] (L = 2,2'-bipyridine (bipy) (1), 4,4'-di-tert-butyl-2,2'-bipyridine (di-tBu-bipy) (2)) by reaction with aqueous tert-butylhydroperoxide (TBHP) or H2O2 gave the following compounds in good to excellent yields: the oxo-bridged dimers [MoO2Cl(L)](2)O (L = bipy (3), di-tBu-bipy (6)) using TBHP(10 equiv.)/CH3CN/r.t.; the molybdenum oxide/bipyridine hybrid material {[MoO3(bipy)][MoO3(H2O)]}(n) (4) and the octanuclear complex [Mo8O24(di-tBu-bipy)(4)] (7) using TBHP(50 equiv.)/H2O/70 degrees C; the oxodiperoxo complexes MoO(O-2)(2)(L) (L = bipy (5), di-tBu-bipy (8)) using H2O2(10 equiv.)/CH3CN/r.t. The structure of 7.x (solvent) (where solvent = CH2Cl2 and/or diethyl ether) was determined by single crystal X-ray diffraction. Despite possessing the same windmill-type complex as that described previously for 7.10CH(2)Cl(2), the crystal structure of 7.x(solvent) is unique due to differences in the crystal packing. Compounds 1-8 were examined as catalysts or catalyst precursors for the epoxidation of cyclooctene using aqueous TBHP or H2O2 as oxidant at 55 or 70 degrees C. Reactions were performed without co-solvent or with the addition of water, ethanol or acetonitrile. Cyclooctene oxide was always the only reaction product. Solids recovered after 24 h reaction at 70 degrees C were identified by FT-IR spectroscopy as the hybrid 4 from (1,3-5)/TBHP, complex 5 from (1,3-5)/H2O2, and complex 8 from (2,6-8)/H2O2. With TBHP as oxidant, the highest epoxide yields (for 24 h reaction at 70 degrees C) were obtained using excess H2O as solvent (28-38% for 1,3-5; 87-98% for 2,6-8), while with H2O2 as oxidant, the highest epoxide yields were obtained using CH3CN as solvent (54-81% for 3-8).
palavras-chave
TERT-BUTYL HYDROPEROXIDE; BOND-VALENCE PARAMETERS; PI-ALLYL COMPLEXES; CRYSTAL-STRUCTURE; TUNGSTEN COMPLEXES; OLEFIN EPOXIDATION; NITROGEN DONOR; OXO MOLYBDENUM; LIGANDS; MO
categoria
Chemistry
autores
Gamelas, CA; Gomes, AC; Bruno, SM; Paz, FAA; Valente, AA; Pillinger, M; Romao, CC; Goncalves, IS
nossos autores
Ana Catarina Costa Gomes Alves
Investigador Auxiliar
Anabela Tavares Aguiar Valente
Investigador Principal
Filipe Alexandre Almeida Paz
Investigador Principal
Isabel Maria de Sousa Gonçalves
Professor associado
Martyn Pillinger
Investigador Principal
Sofia M. Bruno
Investigador Auxiliaragradecimentos
We are grateful to the Fundacao para a Ciencia e a Tecnologia (FCT), the Programa Operacional Ciencia e Inovacao (POCI) 2010, Orcamento do Estado (OE), and Fundo Europeu de Desenvolvimento Regional (FEDER) for general funding, and for financial support (FCT) towards the purchase of the single-crystal diffractometer. The NMR spectrometers are part of The National NMR Network (REDE/1517/RMN/2005), supported by POCI 2010 and the FCT. The FCT and the European Social Fund are acknowledged for a post-doctoral grant to S. M. B (SFRH/BPD/46473/2008). CICECO is acknowledged for financial support (including a post-doctoral research grant to A. C. G.) through the project entitled