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首页> 外文期刊>Catalysis science & technology >Mechanistic study of C-H bond activation by O-2 on negatively charged Au clusters: alpha,beta-dehydrogenation of 1-methyl-4-piperidone by supported Au catalysts dagger
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Mechanistic study of C-H bond activation by O-2 on negatively charged Au clusters: alpha,beta-dehydrogenation of 1-methyl-4-piperidone by supported Au catalysts dagger

机译：机械研究的碳氢键活化坐坐带负电荷的非盟集群:α,beta-dehydrogenation1-methyl-4-piperidone支持非盟的催化剂匕首

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摘要

Au nanoparticles supported on the manganese oxide octahedral molecular sieve OMS-2 can efficiently catalyze alpha,beta-dehydrogenation of beta-N-substituted saturated ketones using O-2 as the terminal oxidant. However, despite the utility of this reaction, the active sites and the reaction mechanism remain unclear. Here, the reaction mechanism for the Au/OMS-2-catalyzed aerobic alpha,beta-dehydrogenation of 1-methyl-4-piperidone was investigated mainly by using density functional theory (DFT) calculations. From control experiments under various reaction conditions, we found that O-2 plays an important role in the alpha,beta-dehydrogenation over Au nanoparticles. Thus, we attempted to clarify the mechanism for the alpha,beta-dehydrogenation of 1-methyl-4-piperidone on Au nanoparticle catalysts by DFT calculations using Au cluster models. The reaction was found to cleave the C-H-alpha and C-H-beta bonds in that order. An O-2 molecule adsorbed on the negatively charged Au cluster caused by charge transfer from OMS-2 was found to be sufficiently activated to abstract the H-alpha atom in the 1-methyl-4-piperidone substrate. This indirect H-alpha abstraction by the activated O-2 was energetically more favorable than direct H-alpha abstraction by the Au cluster. The subsequent H-beta abstraction was found to be promoted by adsorbed oxygen species (i.e., HOO, OH, and O) formed after the H-alpha abstraction. The reaction mechanism proposed in this study provides general insight into the aerobic C-H bond activation by supported Au catalysts.
机译：Au纳米锰氧化物上的支持八面体分子筛OMS-2可以有效催化α,beta-dehydrogenationbeta-N-substituted饱和酮使用0 2终端氧化剂。网站和效用的这个反应,活跃反应机理尚不清楚。非盟/ OMS-2-catalyzed反应机制有氧α,beta-dehydrogenation1-methyl-4-piperidone是主要是通过调查使用密度泛函理论(DFT)计算。各种反应条件,我们发现0 2中发挥着重要作用α,beta-dehydrogenation Au纳米颗粒。因此,我们试图澄清的机制α,beta-dehydrogenation1-methyl-4-piperidone Au纳米粒子上催化剂通过DFT计算使用非盟集群模型。在这个顺序C-H-alpha和C-H-beta债券。0 2分子吸附在带负电荷从OMS-2盟集群由电荷转移引起的被发现充分激活抽象的h - alpha原子1-methyl-4-piperidone衬底。激活0 2 h - alpha抽象的比直接h - alpha大力更有利抽象的非盟集群。被发现由hβ抽象吸附氧物种(例如,HOO,哦,和O)h - alpha抽象后形成的。反应机理提出了研究提供一般的洞察有氧碳氢键激活债券支持非盟的催化剂。

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