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  Electronic Structure of Bis(imino)pyridine Iron Dichloride, Monochloride, and Neutral Ligand Complexes:  A Combined Structural, Spectroscopic, and Computational Study

Bart, S. C., Chlopek, K., Bill, E., Bouwkamp, M. W., Lobkovsky, E., Neese, F., et al. (2006). Electronic Structure of Bis(imino)pyridine Iron Dichloride, Monochloride, and Neutral Ligand Complexes:  A Combined Structural, Spectroscopic, and Computational Study. Journal of the American Chemical Society, 128(42), 13901-13912. doi:10.1021/ja064557b.

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 Creators:
Bart, Suzanne C.1, Author
Chlopek, Krzysztof2, Author              
Bill, Eckhard2, Author              
Bouwkamp, Marco W.1, Author
Lobkovsky, Emil1, Author
Neese, Frank2, Author              
Wieghardt, Karl2, Author              
Chirik, Paul J.1, Author
Affiliations:
1Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, ou_persistent22              
2Research Department Wieghardt, Max Planck Institute for Bioinorganic Chemistry, Max Planck Society, ou_3023881              

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 Abstract: The electronic structure of a family of bis(imino)pyridine iron dihalide, monohalide, and neutral ligand compounds has been investigated by spectroscopic and computational methods. The metrical parameters combined with Mössbauer spectroscopic and magnetic data for (iPrPDI)FeCl2 (iPrPDI = 2,6-(2,6-iPr2C6H3N=CMe)2C5H3N) established a high-spin ferrous center ligated by a neutral bis(imino)pyridine ligand. Comparing these data to those for the single electron reduction product, (iPrPDI)FeCl, again demonstrated a high-spin ferrous ion, but in this case the SFe = 2 metal center is antiferromagnetically coupled to a ligand-centered radical (SL = 1/2), accounting for the experimentally observed S = 3/2 ground state. Continued reduction to (iPrPDI)FeLn (L = N2, n = 1,2; CO, n = 2; 4-(N,N-dimethylamino)pyridine, n = 1) resulted in a doubly reduced bis(imino)pyridine diradical, preserving the ferrous ion. Both the computational and the experimental data for the N,N-(dimethylamino)pyridine compound demonstrate nearly isoenergetic singlet (SL = 0) and triplet (SL = 1) forms of the bis(imino)pyridine dianion. In both spin states, the iron is intermediate spin (SFe = 1) ferrous. Experimentally, the compound has a spin singlet ground state (S = 0) due to antiferromagnetic coupling of iron and the ligand triplet state. Mixing of the singlet diradical excited state with the triplet ground state of the ligand via spin−orbit coupling results in temperature-independent paramagnetism and accounts for the large dispersion in 1H NMR chemical shifts observed for the in-plane protons on the chelate. Overall, these studies establish that reduction of (iPrPDI)FeCl2 with alkali metal or borohydride reagents results in sequential electron transfers to the conjugated π-system of the ligand rather than to the metal center.

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Language(s): eng - English
 Dates: 2006-06-272006-10-01
 Publication Status: Published in print
 Pages: 12
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1021/ja064557b
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Title: Journal of the American Chemical Society
  Other : JACS
  Abbreviation : J. Am. Chem. Soc.
Source Genre: Journal
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Publ. Info: Washington, DC : American Chemical Society
Pages: - Volume / Issue: 128 (42) Sequence Number: - Start / End Page: 13901 - 13912 Identifier: ISSN: 0002-7863
CoNE: https://pure.mpg.de/cone/journals/resource/954925376870