Mechanistic Variants in Methane Activation Mediated by Gold(I) Supported on Silicon Oxide Clusters
Mechanistic Variants in Methane Activation Mediated by Gold(I) Supported on Silicon Oxide Clusters
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氧化硅簇负载的金 (1) 介导的甲烷活化机制变化
DOI：
10.1002/chem.201803432
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
He S.-G.
中科院分区：
文献类型：
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作者：
Chen Y.-M.;Wang L.-N.;Chen J.-J.;Chen Q.;Jiang L.-X.;Zhao Y.-X.;Ding Xun-Lei;He S.-G.
在凝聚相研究中，阳离子金经常被认为是活化甲烷的合适的活性物种。然而，目前还远不清楚协调部位如何操纵这些物种的活动。在这里，通过锚定不同大小的Au离子氧化硅团簇载体，利用质谱学结合量子化学计算阐明了AuI−Oxs对特定位置的甲烷的活化。对于具有不同反应效率的四个甲烷C−H键中的一个选择性地激活甲烷的四个C−H键之一的簇状阴离子Au(SiO_2)NO_ (n=1-3)，发现了一个意想不到的机械开关：通过氧化加成机制(均解过程)锚定在AuSiO_3−或AuSi2O_5−簇上的两配位金离子(AuI， 2f)的效率很低，而通过Lewis酸/碱对机制(AuI，−)负载的单配位金离子(AuI，Alf)的效率很高。 1f⋅⋅⋅O2−，一种异解过程)。氧配体对Au原子5d轨道能级的精细调控是AuI、 2f和Aui、 1f物种之间机理差异的主要原因。在严格的分子水平上对AuI-−-Oxs反应活性的机理理解可以用来阐明不同氧化物载体上固定的金的不同活性。
Cationic gold has been frequently identified as a suitable reactive species for activating methane in condensed‐phase studies. However, it is far from clear how the coordination site manipulates the activity of such species. Herein, by anchoring AuIon silicon oxide cluster supports of variable sizes, the site‐specific methane activation by AuI−Oxhas been clarified by mass spectrometry in conjunction with quantum chemistry calculations. An unexpected mechanistic switch in C−H activation was identified for the cluster anions Au(SiO2)nO−(n=1–3) that selectively activate one of the four C−H bonds of methane with different reaction efficiencies: a low efficiency was observed for the two‐fold‐coordinated gold ion (AuI, 2f), which was anchored on an AuSiO3−or AuSi2O5−cluster, through an oxidative addition mechanism (a homolytic process), and high efficiency was observed for the one‐fold‐coordinated gold ion (AuI, 1f), which was supported on an AuSi3O7−cluster, through Lewis acid/base pairs mechanism (AuI, 1f⋅⋅⋅O2−, a heterolytic process). Fine regulation of the 5d orbital level of the Au atom by the oxygen ligands accounted for the mechanistic difference between AuI, 2fand AuI, 1fspecies. The mechanistic understanding of the reactivity of AuI−Oxat a strictly molecular level can be used to clarify the dissimilar activity of gold anchored on different oxide supports.