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Reduction of Terphenyl Iron(II) Or Cobalt(II)halides in the Presence of Trimethylphosphine: An Unusual Triple Dehydrogenation of an Alkyl Group
Dalton Transactions
  • Chengbao Ni
  • Bobby D. Ellis
  • Troy A. Stich
  • James C. Fettinger
  • Gary J. Long, Missouri University of Science and Technology
  • R. David Britt
  • Philip P. Power
Abstract

The reduction of {ArFeBr}2 (Ar = terphenyl) with KC8 in the presence of excess PMe3 afforded the Fe(i) complex 3,5-Pr i2-Ar′Fe(PMe3) (1) (Ar′-3,5-Pr i2 = C6H-2,6-(C6H 3-2,6-Pri2)-3,5-Pri2), which has a structure very different from the previously reported, linear Cr(i) species 3,5-Pri2-Ar*Cr(PMe3) (3,5-Pr i2-Ar* = C6H-2,6-(C6H 2-2,4,6-Pri3)2-3,5-Pr i2) and features a strong Fe-η6-aryl interaction with the flanking aryl ring of the terphenyl ligand. In sharp contrast, the reduction of {ArCoCl}2 (Ar = 3,5-Pri2-Ar′ and Ar′) afforded the allyl complexes Co(η3-{1-(H2C)2C-C6H 3-2-(C6H2-2,4-Pri2-5-(C6H3-2,6-Pri2))-3-Pri})(PMe3)3 (4) and Co(η3-{1-(H2C)2C-C6H 3-2-(C6H4-3-(C6H3-2,6- Pri2))-3-Pri})(PMe3)3 (5) formed by an unusual triple dehydrogenation of an isopropyl group. It is proposed that the reduction initially generates an intermediate 3,5-Pr i2-Ar′Co(PMe3), which is similar in structure to 1, followed by 3,5-Pri2-Ar′Co(PMe 3) decomposition to a cobalt hydride intermediate and dehydrogenation of the isopropyl group via remote C-H activation induced by PMe3 complexation. Complexes 1, 4, and 5 were characterized by X-ray crystallography. In addition, 1 was studied by NMR and EPR spectroscopy; 4 and 5 were characterized by NMR spectroscopy.

Department(s)
Chemistry
Sponsor(s)
National Science Foundation (U.S.)
Keywords and Phrases
  • Cobalt compounds,
  • Dehydrogenation,
  • Nuclear magnetic resonance,
  • X-ray crystallography
Document Type
Article - Journal
Document Version
Citation
File Type
text
Language(s)
English
Rights
© 2009 Royal Society of Chemistry, All rights reserved.
Publication Date
5-1-2009
Publication Date
01 May 2009
Disciplines
Citation Information
Chengbao Ni, Bobby D. Ellis, Troy A. Stich, James C. Fettinger, et al.. "Reduction of Terphenyl Iron(II) Or Cobalt(II)halides in the Presence of Trimethylphosphine: An Unusual Triple Dehydrogenation of an Alkyl Group" Dalton Transactions (2009) ISSN: 1477-9226
Available at: http://works.bepress.com/gary-long/290/