resumo
Mono-substituted and sandwich-type copper substituted polyoxoanions ([PW11CuO39](5-) and [Cu-4(H2O)(2)(PW9O34)(2)](10-)) were studied as catalysts for the epoxidation of cyclooctene and geraniol, using the green oxidant H2O2, with the. results suggesting good efficiency at room temperature. High selectivity and reasonable conversion data were found after the first minutes of reaction. The copper centre may be responsible for this performance and our on-going research focuses in the preparation of new materials incorporating copper into polyoxometalates (POMs). In this context, we have also isolated a new crystalline dimeric sandwich-type polyoxocoppertungstate {H-7 (05)[Cu3WO(H2O)(CuW9O34)(Cu0.6W9O34)]}(7.75-) . This compound was isolated as potassium salt and structurally characterized by FTIR and single-crystal X-ray diffraction (XRD). The polyoxoanion is composed by the [CuW9O34](12-) and [Cu0.6W9O34](12.8-) anionic fragments, Joined to,ether by a rhomb-like arrangement of three Cu2+ and one W6+ metallic centres, all exhibiting octahedral coordination geometries.
palavras-chave
HYDROGEN-PEROXIDE; ALKENE OXIDATION; TUNGSTOPHOSPHATES; ANIONS; SALTS
categoria
Engineering; Materials Science
autores
Balula, SS; Cunha-Silva, L; Santos, ICMS; Paz, FAA; Rocha, J; Nogueira, HIS; Cavaleiro, AMV
nossos autores
Ana Maria Vieira Silva Viana Cavaleiro
Professor Catedrático
Filipe Alexandre Almeida Paz
Investigador Principal
Helena Isabel Seguro Nogueira
Professor Auxiliar com Agregação
Isabel Cristina Maia da Silva Santos Vieira
Investigador Júnior
João Rocha
Prof. Catedráticoagradecimentos
We are grateful to FCT (MCTES, Portugal) for their general financial support under the POCTI programme (supported by FEDER) and for the grants SFRH/BPD/14410/2003 (to S.S.B.), SFRH/BPD/11647/2002 (to L.C.-S.) and SFRH/BPD/14613/2003 (to I.C.M.S.S.)