resumo
A new organosilica hybrid mesoporous material (HM) containing phosphane oxide surface groups was prepared via the "dual" organosilane templated co-condensation of 4-bis-(triethoxysilyl)benzene and (diphenylphosphanyl)propyltriethoxysilane, followed by post-synthesis oxidation of the phosphane surface groups. The HM material was used to immobilise the [Mo(O)(2)Cl(2)] complex. The resultant material (HM-Mo) is an active and selective catalyst in the liquid-phase epoxidation of olefins [cis-cyclooctene, (R)-(+)-limonene, trans-2-octene, 1-octene] with tBuOOH at 55 degrees C and gives comparable epoxide yields to those observed for the free complex [MoCl(2)(O)(2){OP(CH(2)CH(3))(Ph)(2)}(2)] (1), under similar reaction conditions: the crystal structure of complex 1 remains the same after reaction with tBuOOH. The oxidant is essentially consumed in the HM-Mo or 1 catalysed epoxidation of the olefin. In the case of limonene (possesses endo- and exocyclic C=C bonds), the molar ratio of 1,2-epoxy-p-menth-8-ene/1,2-8,9-diepoxy-p-menthane at ca. 90% conversion (reached after 24 h reaction) is ca. 5 and 10 for 1 and HM-Mo, respectively, indicating a favourable regioselectivity towards the epoxidation of the endocyclic C1-C2 double bond, especially in the case of the heterogeneous catalyst.
palavras-chave
MESOPOROUS MCM-41 MATERIALS; INORGANIC HYBRID MATERIALS; TERT-BUTYL HYDROPEROXIDE; PHOSPHINE OXIDE LIGANDS; HETEROGENEOUS CATALYSTS; ALKENE EPOXIDATION; CRYSTAL-STRUCTURES; COMPLEXES BEARING; LEWIS-BASE; MOLYBDENUM(VI)
categoria
Chemistry
autores
Castro, A; Alonso, JC; Valente, AA; Neves, P; Brandao, P; Felix, V; Ferreira, P
nossos autores
Anabela Tavares Aguiar Valente
Investigador Principal
Patrícia dos Santos Neves
Investigador Auxiliar
Paula Celeste da Silva Ferreira
Investigador Coordenador
Paula Cristina Ferreira da Silva Brandão
Investigador Auxiliar
Vítor Félix
Professor Associado com AgregaçãoGrupos
G1 - Materiais Porosos e Nanossistemas
G2 - Materiais Fotónicos, Eletrónicos e Magnéticos
G4 - Materiais Renováveis e Economia Circular
G6 - Materiais Virtuais e Inteligência Artificial
agradecimentos
The authors are grateful to the Programa Operacional Ciencia e Inovacao/2010, the Fundo Europeu de Desenvolvimento Regional and the Fundacao para a Ciencia e a Tecnologia for financial support (POCI/CTM/55648/2004 and PPCDT/CTM/55648/2004).