Premium
Activation of aromatic rings by early transition metal ions in the gas phase. Implications for the metal‐catalyzed [2 + 2 + 2] cycloaddition of alkynes and nitriles
Author(s) -
Pope R. Marshall,
Buckner Steven W.
Publication year - 1993
Publication title -
organic mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0030-493X
DOI - 10.1002/oms.1210281238
Subject(s) - cycloaddition , catalysis , aromaticity , transition metal , gas phase , metal , chemistry , ion , metal ions in aqueous solution , photochemistry , inorganic chemistry , organic chemistry , molecule
The reactions of a series of monocyclic and bicyclic arenes with early transition metal ions (Sc + , Y + , Nb + and Ta + ) and their oxides and dioxides were studied in a Fourier transform ion cyclotron resonance mass spectrometer. Ring cleavage of the nitrogen‐containing heterocycles results in loss of HCN as the dominant pathway. Thermochemical considerations, secondary reactions and correlations with solution cyclotrimerization reactions indicate that the MC 4 H 4 + product is a metallacyclopentadiene. Based on correspondence between the reactivities of a series of early metals with their valence electron counts, the reactivities of quinoline and isoquinoline and the decomposition behavior of the products, a metallacycloheptatriene intermediate is proposed for the heteroaromatic ring cleavage reaction. These results are compared to metal complexes in solution which catalyze the [2 + 2 + 2] cyclotrimerization of alkynes and nitriles.