کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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66883 | 48456 | 2010 | 8 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: Factors influencing recyclability of Co(III)-salen catalysts in the hydrolytic kinetic resolution of epichlorohydrin Factors influencing recyclability of Co(III)-salen catalysts in the hydrolytic kinetic resolution of epichlorohydrin](/preview/png/66883.png)
The recyclability of Co(III)-salen catalysts, where salen is defined by (R,R)-N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediamine, for the hydrolytic kinetic resolution (HKR) of racemic epichlorohydrin is a strong function of the counterion of the Co(III)-salen catalyst. The nature of the counterion determines whether the HKR reaction follows primarily a bimetallic or monometallic reaction path, which significantly affects catalyst recyclability. For example, Co(III)-salen initially containing the nucleophilic Cl− counterion catalyzes the HKR of epichlorohydrin according to a bimetallic reaction path but loses activity upon recycle, as Cl− is replaced with OH− during the reaction. In contrast, a Co(III)-salen catalyst containing non-nucleophilic SbF6− counterion catalyzes the reaction according to a monometallic reaction path and is quite stable during multiple recycles, albeit at a low rate with less selectivity. A mixed catalyst system with Co(III)-salen initially containing Cl− to which Co(III)-salen with SbF6− is later added demonstrates high activity and high stability to recycling. Additional experiments with Co(III)-salen initially containing the acetate counterion reveal a progressive decline in activity with multiple recycles even after regeneration with acetic acid between runs, suggesting a destructive role of the regeneration process.
The recyclability of Co(III)-salen catalysts for the hydrolytic kinetic resolution of racemic epichlorohydrin is a strong function of the counterion of the Co(III)-salen catalyst. The nature of the counterion determines whether the HKR reaction follows primarily a bimetallic or monometallic reaction path, which significantly affects catalyst recyclability.Figure optionsDownload high-quality image (41 K)Download as PowerPoint slide
Journal: Journal of Molecular Catalysis A: Chemical - Volume 316, Issues 1–2, 1 February 2010, Pages 8–15