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Study of the influence of PPh3 used as capping ligand or as reaction modifier for hydroformylation reaction involving Rh NPs as precatalyst
Applied Catalysis A: General ( IF 5.5 ) Pub Date : 2017-08-10 , DOI: 10.1016/j.apcata.2017.08.009
Marco A.S. Garcia , Mahmoud Ibrahim , Jean C.S. Costa , Paola Corio , Elena V. Gusevskaya , Eduardo N. dos Santos , Karine Philippot , Liane M. Rossi

The presence of capping ligands on the surface of metal nanoparticles (NPs) has been recognized to be a key factor for the control of their size and shape as well as for their stabilization, but their influence on the NP behavior in catalysis is far from being well-understood. Here, we investigated the performance of Rh NPs stabilized by tetraoctylammonium bromide (Rh-TOAB NPs) when applied as precatalyst for hydroformylation reaction. An ehnancement of the catalytic activity was clearly observed after adding monophosphines as a reaction modifier. More interestingly, a much higher effect was observed when a phosphine was directly used as capping ligand for the synthesis of the Rh particles, i.e. in the absence of TOAB. Indeed, triphenylphosphine-stabilized Rh NPs (Rh-PPh3 NPs) were found to be a unique precursor for hydroformylation active catalytic species, leading to higher activity attributed to the existence of a strong phosphine-rhodium interaction in this case. The Rh-PPh3 NPs appeared less affected when adding poisoning ligands in catalytic reaction than the Rh-TOAB NPs PPh3 system which deactivates in the presence of CS2. In addition, a large excess (20 equiv. per Rh atom) of PPh3 was necessary to activate the Rh-TOAB NPs, similarly to the amount typically used in homogeneous catalytic systems. In the contrary, one equiv. of PPh3 (per Rh atom) was enough to prepare Rh-PPh3 NPs, which are more active and more stable against CS2 poisoning. All together our results evidence that a direct interaction of PPh3 ligand at the surface of Rh NPs plays an important role on their behavior in hydroformylation catalysis.



中文翻译:

PPh 3用作封端配体或反应改性剂对以Rh NPs为前催化剂的加氢甲酰化反应影响的研究

金属纳米颗粒(NPs)表面上存在封端配体已被认为是控制其尺寸和形状以及稳定性的关键因素,但它们对催化中NP行为的影响远非如此。完全了解。在这里,我们研究了四辛基溴化铵(Rh-TOAB NPs)用作加氢甲酰化反应的预催化剂时稳定的Rh NPs的性能。加入单膦类作为反应改性剂后,可以明显观察到催化活性的增强。更有趣的是,观察到高得多的效果时的膦直接用作封端配体对Rh粒子的合成,。在没有TOAB的情况下。实际上,三苯基膦稳定的Rh NPs(Rh-PPh 3已发现NPs是加氢甲酰化活性催化物种的独特前体,在这种情况下由于存在强烈的膦-铑相互作用而导致更高的活性。与在CS 2存在时会失活的Rh-TOAB NPs PPh 3体系相比,在催化反应中添加中毒配体时,Rh-PPh 3 NP受到的影响较小。另外,与均相催化体系中通常使用的量类似,需要大量过量的PPh 3(每个Rh原子20当量)来活化Rh-TOAB NP。相反,一个当量。PPh 3的数量(每个Rh原子)足以制备Rh-PPh 3 NP,它们对CS 2具有更高的活性和稳定性中毒。所有我们的结果共同证明,Rh NPs表面PPh 3配体的直接相互作用对其加氢甲酰化催化的行为起重要作用。

更新日期:2017-08-10
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