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Electronic Structure–Reactivity Relationship on Ruthenium Step-Edge Sites from Carbonyl 13C Chemical Shift Analysis
The Journal of Physical Chemistry Letters ( IF 5.7 ) Pub Date : 2018-05-31 00:00:00 , DOI: 10.1021/acs.jpclett.8b01332
Lucas Foppa 1 , Keishi Yamamoto 1 , Wei-Chih Liao 1 , Aleix Comas-Vives 1 , Christophe Copéret 1
Affiliation  

Ru nanoparticles are highly active catalysts for the Fischer–Tropsch and the Haber–Bosch processes. They show various types of surface sites upon CO adsorption according to NMR spectroscopy. Compared to terminal and bridging η1 adsorption modes on terraces or edges, little is known about side-on η2 CO species coordinated to B5 or B6 step-edges, the proposed active sites for CO and N2 cleavage. By using solid-state NMR and DFT calculations, we analyze 13C chemical shift tensors (CSTs) of carbonyl ligands on the molecular cluster model for Ru nanoparticles, Ru624-CO)2(CO)136-C6Me6), and show that, contrary to η1 carbonyls, the CST principal components parallel to the C–O bond are extremely deshielded in the η2 species due to the population of the C–O π* antibonding orbital, which weakens the bond prior to dissociation. The carbonyl CST is thus an indicator of the reactivity of both Ru clusters and Ru nanoparticles step-edge sites toward C–O bond cleavage.

中文翻译:

羰基13 C化学位移分析在钌台阶边缘位点上的电子结构-反应性关系

钌纳米颗粒是费-托和哈伯-博世过程的高活性催化剂。根据NMR光谱,它们在CO吸附时显示出各种类型的表面位点。相比于终端和桥接η 1种上露台或边缘吸附模式,知之甚少侧上η 2个配位至B CO物种5或B 6步的边缘,对CO和N所提出的活性位点2切割。通过使用固态NMR和DFT计算,我们分析13上的Ru纳米颗粒的分子簇模型羰基配体的c。化学位移张量(技术服务小组),钌6(η 24 -CO)2(CO)13(η 6 -C 66),和显示,相反至η 1个羰基,该CST主成分平行于C-O键在η都极为去屏蔽2种由于的C-Oπ人口*反键轨道,在离解之前会弱化键。因此,羰基CST是Ru团簇和Ru纳米颗粒台阶边缘位点对C-O键断裂的反应性指标。
更新日期:2018-05-31
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