K10-montmorillonite as support for a cationic manganese(III)-salen complex

• Autor(a) principal: Kuźniarska-Biernacka,Iwona
• Data de Publicação: 2009
• Outros Autores: Pereira,Clara, Carvalho,Ana P., Pires,João, Freire,Cristina
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Journal of the Brazilian Chemical Society (Online)
• Texto Completo: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532009000700017
• topic: K10-montmorillonite; alkene epoxidation; catalyst support; manganese(III)-salen

A commercial K10-montmorillonite was used as support for the immobilization of a cationic manganese(III)-salen complex. The catalytic behavior of the resulting material was tested in the enantioselective epoxidation of three different alkenes, viz.: styrene, α-methylstyrene and 6-cyano-2,2-dimethylchromene, at 0 ºC, using three different oxidant systems: m-chloroperoxybenzoic acid (m-CPBA) and N-methylmorpholine (NMO) as co-oxidant, iodosylbenzene (PhIO) and sodium hypochlorite. All samples, before and after the catalytic studies, were characterised by nitrogen adsorption at -196 ºC, DRX, FTIR and chemical analysis, in order to evaluate the influence of the substrate/oxidant system on catalyst integrity. The catalytic results demonstrated a strong influence of the substrate and oxidant system on the enantiomeric excess (%ee) values. In some cases, these values were comparable to those in the corresponding homogeneous phase reactions. The results also highlighted the importance of optimizing the oxidant systems, since they may lead to the disruption of the complex from the support, and the consequent catalyst deactivation.