Mn(I)-Induced 1,6-Demethanation across the CC Triple Bond of Linear Alkynes in the Gas Phase. A Case for the Generation of Manganese Cycloalkynes?

Article abstract of DOI:10.1021/ja00209a010

Complexes of Mn(alkynes)⁺ were generated in the gas phase and found to exhibit a reactivity which is even richer than that of the analogous Fe(alkyne)⁺ species.Among the many unimolecular dissociations, the Mn⁺-induced demethanation of 4-octyne is of particular interest.The study of isotopomers and the effects of alkyl chain lengths reveals the operation of an unprecedented 1,6-elimination mode across the CC triple bond, and the experimental results may be explained by invoking the intermediate generation of the as yet unknown metallacycloalkynes.The implications of the unexpected, rich gas-phase ion chemistry of Mn⁺ with regard to theoretical models are discussed.