Unexpected CNN-to-CC Ligand Rearrangement in Pincer–Ruthenium Precatalysts Leads to a Base-Free Catalyst for Ester Hydrogenation,Organometallics

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Unexpected CNN-to-CC Ligand Rearrangement in Pincer–Ruthenium Precatalysts Leads to a Base-Free Catalyst for Ester Hydrogenation
Organometallics ( IF 2.5 ) Pub Date : 2019-07-22 , DOI: 10.1021/acs.organomet.9b00373
Linh Le ₁ , Jiachen Liu ₁ , Tianyi He ₁ , Jack C. Malek ₁ , Tia N. Cervarich ₁ , John C. Buttner ₁ , John Pham ₁ , Jason M. Keith ₁ , Anthony R. Chianese ₁

Affiliation

We report the conversion of a series of CNN–pincer–ruthenium complexes Ru(CNN)HCl(CO) to a CC-chelated form Ru(CC)(PR₃)₂H(CO) on reaction with sodium tert-butoxide and monodentate phosphines. When the phosphine is triphenylphosphine, cis-phosphine complexes form at room temperature, which convert to the trans isomer at elevated temperatures. When the phosphine is tricyclohexylphosphine, only the trans-phosphine isomer is observed. The CC-chelated complexes are active catalysts for the hydrogenation of esters, without the need for added base. The ligand structure–activity relationship in the series of CC-chelated complexes mirrors that in the precursor CNN-Ru complexes, potentially indicating a common catalytic mechanism. Density functional theory calculations establish a plausible mechanism for the CNN-to-CC rearrangement and demonstrate that this rearrangement is potentially reversible under the conditions of ester hydrogenation catalysis.

中文翻译：

cer-钌预催化剂中CNN到CC的配体意外重排导致酯加氢的无碱催化剂

我们报告了一系列CNN-钳子-钌络合物Ru（CNN）HCl（CO）与叔丁醇钠和单齿钠反应转化为CC螯合形式的Ru（CC）（PR ₃）₂ H（CO）。膦。当膦是三苯基膦时，在室温下形成顺式膦配合物，其在升高的温度下转化为反式异构体。当膦是三环己基膦时，只有反式观察到-膦异构体。CC螯合的络合物是酯加氢的活性催化剂，无需添加碱。CC螯合配合物系列中的配体结构与活性之间的关系反映了前体CNN-Ru配合物中的配体结构与活性之间的关系，这潜在地表明了一种共同的催化机理。密度泛函理论计算建立了CNN到CC重排的合理机制，并证明了这种重排在酯加氢催化条件下是可逆的。

更新日期：2019-07-22

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