Synthesis and catalytic properties in olefin epoxidation of dioxomolybdenum(vi) complexes bearing a bidentate or tetradentate salen-type ligand

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• 作者：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. Gonç ; alves
• 关键词：Molybdenum ; Oxide complexes ; Salen-type ligands ; Pyrrole derivatives ; Epoxidation
• 刊名：Journal of Molecular Catalysis A ; Chemical
• 出版年：2007
• 期刊代码：57_13811169
• 类别：ch
• 出版时间：1 June 2007
• 卷：270
• 期：1-2
• 页码：185-194
• 文件大小：407 K

摘要

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.