Mechanistic Aspects of the Reaction of Anionic Iron(0)-Olefin Complexes with Organic Halides. Detection and Characterization of Paramagnetic Organometallic Intermediates

Dale H. Hill, Masood A. Parvez, Ayusman Sen

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48 Scopus citations

Abstract

The scope and the mechanism of the reactions of [CpFe(COD)] [Li(TMEDA) (Cp = C5H5-; COD = 1, 5-cyclooctadiene; TMEDA = Me2NCH2CH2NMe2), 1, with a number of organic monohalides and geminal dihalides were investigated. With monohalides organic coupling products were observed, and, in particular, the coupling and cross-coupling of benzyl and allyl halides were studied in detail. The addition of 1 equiv of benzyl halide to 1 in benzene resulted in the initial formation of [CpFe(COD)(CH2Ph)], 7. The predominant pathway involved an initial one-electron transfer from [CpFe(COD)]- to PhCH2X to form PhCH2- and [CpFe(COD)]˙. PhCH2- quickly disproportionated to form PhCH2X˙ and X-. The benzyl radical then added to [CpFe(COD)]˙. Once formed [CpFe-(COD)(CH2Ph)] reacted with TMEDA in a disproportionate reaction to form 0.5 equiv of the paramagnetic compound, [(TMEDA)Fe(CH2Ph)2], 3, and 0.5 equiv of FeCp2. When additional benzyl (or allyl) halide was added, it reacted with [(TMEDA)Fe(CH2Ph)2] to form the coupled (or cross-coupled) product. This coupling reaction involved the intermediacy of benzyl (and allyl) radicals, and the experimental results were consistent with the product being formed by the coupling of two radicals in solution.

Original languageEnglish (US)
Pages (from-to)2889-2901
Number of pages13
JournalJournal of the American Chemical Society
Volume116
Issue number7
DOIs
StatePublished - Apr 1 1994

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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