abstract
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.
keywords
SCHIFF-BASE LIGANDS; CIS-DIOXO COMPLEXES; MOLYBDENUM; DERIVATIVES; TRIDENTATE; MECHANISM; OXIDATION; N,N'-ETHYLENEBIS(SALICYLIDENEIMINE); DIOXOTUNGSTEN(VI); DICHLORO
subject category
Chemistry
authors
Bruno, SM; Balula, SS; Valente, AA; Paz, FAA; Pillinger, M; Sousa, C; Klinowski, J; Freire, C; Ribeiro-Claro, P; Goncalves, IS
our authors
Anabela Tavares Aguiar Valente
Principal Researcher
Filipe Alexandre Almeida Paz
Principal Researcher
Isabel Maria de Sousa Gonçalves
Associate Professor
Martyn Pillinger
Principal Researcher
Paulo Ribeiro-Claro
Associate Professor with Aggregation