Universität zu Köln

Li, Jilai ORCID: 0000-0002-3363-9164, Zhou, Shaodong ORCID: 0000-0003-3048-4678, Zhang, Jun, Schlangen, Maria ORCID: 0000-0002-8783-6788, Weiske, Thomas ORCID: 0000-0003-4756-2548, Usharani, Dandamudi, Shaik, Sason and Schwarz, Helmut ORCID: 0000-0002-3369-7997 (2016). Electronic Origins of the Variable Efficiency of Room-Temperature Methane Activation by Homo- and Heteronuclear Cluster Oxide Cations [XYO2](+) (X, Y = Al, Si, Mg): Competition between Proton-Coupled Electron Transfer and Hydrogen-Atom Transfer. J. Am. Chem. Soc., 138 (25). S. 7973 - 7982. WASHINGTON: AMER CHEMICAL SOC. ISSN 1520-5126

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Abstract

The reactivity of the homo- and heteronuclear oxide clusters [XYO2](+) (X, Y = Al, Si, Mg) toward methane was studied using Fourier transform ion cyclotron resonance mass spectrometry, in conjunction with high-level quantum mechanical calculations. The most reactive cluster by both experiment and theory is [Al2O2](center dot+). In its favorable pathway, this cluster abstracts a hydrogen atom by means of proton-coupled electron transfer (PCET) instead of following the conventional hydrogen-atom transfer (HAT) route. This mechanistic choice originates in the strong Lewis acidity of the aluminum site of [Al2O2](center dot+), which cleaves the C-H bond heterolytically to form an Al-CH3 entity, while the proton is transferred to the bridging oxygen atom of the cluster ion. In addition, a comparison of the reactivity of heteronuclear and homonuclear oxide clusters [XYO2](+) (X, Y = Al, Si, Mg) reveals a striking doping effect by aluminum. Thus, the vacant s-p hybrid orbital on Al acts as an acceptor of the electron pair from methyl anion (CH3-) and is therefore eminently important for bringing about thermal methane activation by PCET. For the Al-doped cluster ions, the spin density at an oxygen atom, which is crucial for the HAT mechanism, acts here as a spectator during the course of the PCET mediated C-H bond cleavage. A diagnostic plot of the deformation energy vis-a-vis the barrier shows the different HAT/PCET reactivity map for the entire series. This is a strong connection to the recently discussed mechanism of oxidative coupling of methane on magnesium oxide surfaces proceeding through Grignard-type intermediates.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Li, Jilai UNSPECIFIED orcid.org/0000-0002-3363-9164 UNSPECIFIED Zhou, Shaodong UNSPECIFIED orcid.org/0000-0003-3048-4678 UNSPECIFIED Zhang, Jun UNSPECIFIED UNSPECIFIED UNSPECIFIED Schlangen, Maria UNSPECIFIED orcid.org/0000-0002-8783-6788 UNSPECIFIED Weiske, Thomas UNSPECIFIED orcid.org/0000-0003-4756-2548 UNSPECIFIED Usharani, Dandamudi UNSPECIFIED UNSPECIFIED UNSPECIFIED Shaik, Sason UNSPECIFIED UNSPECIFIED UNSPECIFIED Schwarz, Helmut UNSPECIFIED orcid.org/0000-0002-3369-7997 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-271973
DOI:	10.1021/jacs.6b03798
Journal or Publication Title:	J. Am. Chem. Soc.
Volume:	138
Number:	25
Page Range:	S. 7973 - 7982
Date:	2016
Publisher:	AMER CHEMICAL SOC
Place of Publication:	WASHINGTON
ISSN:	1520-5126
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language H BOND ACTIVATION; CHARGE-TRANSFER REACTIONS; GAS-PHASE ACTIVATION; C-H; THERMAL-ACTIVATION; TRANSFER MECHANISMS; EXCHANGE REACTIONS; MAGNESIUM-OXIDE; METAL-COMPLEXES; REACTIVITY Multiple languages Chemistry, Multidisciplinary Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/27197