On the Mechanism of Fe+-Induced Hydrogen Migrations in Gaseous Octyne/Iron(I) Complexes

Christian Schulze, Helmut Schwarz, David A. Peake, Michael L. Gross

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54 Scopus citations

Abstract

The study of D-labeled isomeric octynes provides a detailed insight into the gas-phase chemistry of this prototypic hydrocarbon with bare Fe+. The results not only clearly establish that ^-hydrogen transfer is indeed involved in many major decomposition routes, thus providing firm experimental evidence for this often invoked reaction, but also serve as evidence for some unprecedented reactions. Among these reactions is a site-specific 1,2-dehydrogenation of Fe(2-octyne)+, which serves as a further example for “remote functionalization” proceeding via metallacycles. Another of these reactions is the loss of ethylene from the C(1)/C(2) of Fe(4-octyne)+, where, if described in terms of the traditional sequence of oxidative addition/0-hydrogen transfer/reductive elimination, the 0-hydrogen transfer to the metal ion is not reversible nor does the reaction constitute the rate-determining step of the overall process. More likely is a process in which a metallacycle is involved. Evidence is presented that the metal ion not only inserts into the activated propargylic C-C bond but also inserts into the homopropargylic, to some extent, and even less activated C-C bonds. Ethylene loss from Fe(4-octyne)+complexes is associated with an isotope effect of kH/kD=1.1 per deuterium. The rarely observed 0-alkyl migrations are not involved in the gas-phase chemistry of Fe(octyne)+complexes.

Original languageEnglish
Pages (from-to)2368-2374
Number of pages7
JournalJournal of the American Chemical Society
Volume109
Issue number8
DOIs
StatePublished - Apr 1 1987

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