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Striking Doping Effects on Thermal Methane Activation Mediated by the Heteronuclear Metal Oxides [ X AlO 4 ] .+ ( X =V, Nb, and Ta)
Author(s) -
Wu XiaoNan,
Li Jilai,
Schlangen Maria,
Zhou Shaodong,
GonzálezNavarrete Patricio,
Schwarz Helmut
Publication year - 2017
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201605226
Subject(s) - heteronuclear molecule , chemistry , reactivity (psychology) , oxide , methane , ionic bonding , inorganic chemistry , metal , density functional theory , catalysis , cluster (spacecraft) , ion , computational chemistry , molecule , organic chemistry , medicine , alternative medicine , pathology , computer science , programming language
The thermal reactivity of the heteronuclear metal‐oxide cluster cations [ X AlO 4 ] .+ ( 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, [VAlO 4 ] .+ 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.