Journal article
C–H bond activation versus ring cleavage in the gas phase ion-molecule reactions of Nb + and Ta + with toluene and picoline
International journal of mass spectrometry, Vol.182, pp.197-201
03/01/1999
DOI: 10.1016/S1387-3806(98)14246-X
Abstract
The reactions of Nb
+ and Ta
+ with toluene and picoline and their deuterium-labelled analogues were studied in a Fourier transform ion cyclotron resonance mass spectrometer. Methyl substitution completely changes the reactivities relative to benzene and pyridine. Both metals react to dehydrogenate toluene exclusively. In contrast to benzene, no ring cleavage is observed in the Ta
+/toluene reaction. A simple explanation for this difference in reactivities is proposed based on the relative energies of the Hückel orbitals of benzene and toluene. The (
b
1) symmetric antibonding orbital is higher in energy for toluene. Population of this orbital is necessary for formation of the metallanorbornadiene intermediate and does not occur at thermal energies. Reaction with ring labelled toluene-
d
5 shows exclusive H
2 or D
2 elimination in reaction with Nb
+ and H
2, HD, and D
2 elimination in reaction with Ta
+. Reactions with the picolines show both dehydrogenation and ring cleavage. Isotope labelling studies show facile H/D scrambling occurs in the intermediate ion-molecule complexes with HCN and DCN both eliminated from the methyl-
d
3-2-picoline and 4-picoline. The metals react with picoline and pyridine by different mechanisms. The isotope labelling results suggest a metal-hydrido-azepinium structure for the intermediate complex.
Details
- Title: Subtitle
- C–H bond activation versus ring cleavage in the gas phase ion-molecule reactions of Nb + and Ta + with toluene and picoline
- Creators
- Steven W. Buckner - Columbus State UniversityR.Marshall Pope - University of North Carolina at Chapel Hill
- Resource Type
- Journal article
- Publication Details
- International journal of mass spectrometry, Vol.182, pp.197-201
- Publisher
- Elsevier B.V
- DOI
- 10.1016/S1387-3806(98)14246-X
- ISSN
- 1387-3806
- eISSN
- 1873-2798
- Language
- English
- Date published
- 03/01/1999
- Academic Unit
- Medicine Administration
- Record Identifier
- 9984632125402771
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