resumo
The monomeric cis-dioxomolybdenum(VI)complexes [MoO(2)(oep-saldpen)] and [MoO(2)Cl(2)(oep-H(2)saldpen)], with a tetradentate [N(2)(imine)O(2)] and bidentate [N(2)(imine)] salen-type ligand functionalised with two pyrrole derivative pendant arms [oep-H(2)saldpen = 1,2-diphenylethylenebis(3-oxyethylpyrrole)salicylideneimine], were synthesised and characterised by (1)H NMR, IR and Raman spectroscopy. The solid-state structure of the free ligand oep-H(2)saldpen was determined by single crystal X-ray diffraction. Assignment of the vibrational spectra of the molybdenum complexes was supported by carrying out ab initio calculations for the possible isomers using [MoO(2)(salen)] and [MoO(2)Cl(2)(H(2)salen)] as model compounds [H(2)salen = N,N '-ethylenebis(salicylideneimine)]. The oep-saldpen complexes were examined as catalysts for the epoxidation of cyclooctene, (R)(+)-limonene, styrene, alpha-pinene, and cis and trans-beta-methylstyrene, with tert-butyl hydroperoxide as the oxidant. Both complexes exhibited high selectivity for the epoxidation reaction, with the bis(chloro) complex being always the more active of the two. (C) 2007 Elsevier B.V. All rights reserved.
palavras-chave
SCHIFF-BASE LIGANDS; CIS-DIOXO COMPLEXES; MOLYBDENUM; DERIVATIVES; TRIDENTATE; MECHANISM; OXIDATION; N,N'-ETHYLENEBIS(SALICYLIDENEIMINE); DIOXOTUNGSTEN(VI); DICHLORO
categoria
Chemistry
autores
Bruno, SM; Balula, SS; Valente, AA; Paz, FAA; Pillinger, M; Sousa, C; Klinowski, J; Freire, C; Ribeiro-Claro, P; Goncalves, IS
nossos autores
Ana Sofia Madureira Bruno
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