Striking Doping Effects on Thermal Methane Activation Mediated by the Heteronuclear Metal Oxides [XAlO₄]^.+ (X=V, Nb, and Ta)

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• 作者：Dr. Xiao-Nan Wu ; Prof. Dr. Jilai Li ; Dr. Maria Schlangen ; Dr. Shaodong Zhou ; Dr. Patricio Gonzá ; lez-Navarrete and Prof. Dr. Helmut Schwarz
• 刊名：Chemistry - A European Journal
• 出版年：2017
• 出版时间：January 18, 2017
• 年：2017
• 卷：23
• 期：4
• 页码：788-792
• 全文大小：1436K
• ISSN：1521-3765

文摘

The thermal reactivity of the heteronuclear metal-oxide cluster cations [XAlO₄]^.+ (X=V, Nb, and Ta) towards methane has been studied by using mass spectrometry in conjunction with quantum mechanical calculations. Experimentally, a hydrogen-atom transfer (HAT) from methane is mediated by all the three oxide clusters at ambient conditions. However, [VAlO₄]^.+ is unique in that this cluster directly transforms methane into formaldehyde. The absence of this reaction for the Nb and Ta analogues demonstrates a striking doping effect on the chemoselectivity in the conversion of methane. Mechanistic aspects of the two reactions have been elucidated by quantum-chemical calculations. The HAT reactivity can be attributed to the significant spin density localized at the terminal oxygen atom (O_t^.−) of the cluster ions, while the ionic/covalent character of the Lewis acid–base unit [X−O_b] plays a crucial role for the generation of formaldehyde. The mechanistic insight derived from this combined experimental/computational investigation may provide guidance for a more rational design of catalysts.