Catalytic Properties of the Dioxomolybdenum Siloxide MoO2(OSiPh3)2 and its 2,2'-Bipyridine Adduct MoO2(OSiPh3)2(bpy)

Molecules

Sofia M. Bruno¹  Bernardo Monteiro¹  Maria Salete Balula¹  Catarina Lourenço¹  Anabela A. Valente¹  Martyn Pillinger¹  Paulo Ribeiro-Claro¹ 

[1] Department of Chemistry, CICECO, University of Aveiro, 3810-193 Aveiro, Portugal

关键词: Dioxomolybdenum(VI) complexes;    siloxide ligands;    Lewis base adducts;    2;    2'-bipyridine;    olefin epoxidation;   

DOI  :  10.3390/11040298

来源: mdpi

【 摘 要 】

The tetrahedral triphenylsiloxy complex MoO₂(OSiPh₃)₂ (1) and its Lewis base adduct with 2,2'-bipyridine, MoO₂(OSiPh₃)₂(bpy) (2), were prepared and characterised by IR/Raman spectroscopy, and thermogravimetric analysis. Both compounds catalyse the epoxidation of cis-cyclooctene at 55 ºC using tert-butylhydroperoxide (t-BuOOH) is decane as the oxidant, giving 1,2-epoxycyclooctane as the only product. The best results were obtained in the absence of a co-solvent (other than the decane) or in the presence of 1,2-dichloroethane, while much lower activities were obtained when hexane or acetonitrile were added. With no co-solvent, catalyst 1 (initial activity 272 mol·mol_Mo^‑1·h^‑1 for a catalyst:substrate: oxidant molar ratio of 1:100:150 is much more active than 2 (initial activity 12 mol·mol_Mo^–1·h^–1. The initial reaction rates showed first order dependence with respect to the initial concentration of olefin. With respect to the initial amount of oxidant, the rate order dependence for 1 (1.9) was higher than that for 2 (1.6). The dependence of the initial reaction rate on reaction temperature and initial amount of catalyst was also studied for both catalysts. The lower apparent activation energy of 1 (11 kcal·mol^–1) as compared with 2 (20 kcal·mol^–1) is in accordance with the higher activity of the former.

【 授权许可】

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