Synthesis and catalytic properties in olefin epoxidation of dioxomolybdenum(vi) complexes bearing a bidentate or tetradentate salen-type ligand |
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Authors: | Sofia M Bruno Salete S Balula Anabela A Valente Filipe A Almeida Paz Martyn Pillinger Carla Sousa Jacek Klinowski Cristina Freire Paulo Ribeiro-Claro Isabel S Gonalves |
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Institution: | aDepartment of Chemistry, CICECO, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal;bREQUIMTE, Departamento de Química, Faculdade de Ciências, Universidade do Porto, 4169-007 Porto, Portugal;cDepartment of Chemistry, University of Cambridge, Lensfield Road, CB2 1EW Cambridge, United Kingdom |
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Abstract: | The monomeric cis-dioxomolybdenum(VI) complexes MoO2(oep-saldpen)] and MoO2Cl2(oep-H2saldpen)], with a tetradentate N2(imine)O2] and bidentate N2(imine)] salen-type ligand functionalised with two pyrrole derivative pendant arms oep-H2saldpen = 1,2-diphenylethylenebis(3-oxyethylpyrrole)salicylideneimine], were synthesised and characterised by 1H NMR, IR and Raman spectroscopy. The solid-state structure of the free ligand oep-H2saldpen 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 MoO2(salen)] and MoO2Cl2(H2salen)] as model compounds H2salen = N,N′-ethylenebis(salicylideneimine)]. The oep-saldpen complexes were examined as catalysts for the epoxidation of cyclooctene, (R)-(+)-limonene, styrene, α-pinene, and cis and trans-β-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. |
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Keywords: | Molybdenum Oxide complexes Salen-type ligands Pyrrole derivatives Epoxidation |
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