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Synthesis and characterisation of halide, separated ion pair, and hydride cyclopentadienyl iron bis(diphenylphosphino)ethane derivatives

Evans, David J.; Liddle, Stephen T.; Patel, Dipti; Blake, Alexander J.; Cornish, Andrew D.; Davies, E. Stephen; Lewis, William; McMaster, Jonathan; Steven, Lindsey; Wooles, Ashley

Authors

David J. Evans

Stephen T. Liddle

Dipti Patel

Alexander J. Blake

Andrew D. Cornish

E. Stephen Davies

William Lewis

Jonathan McMaster

Lindsey Steven

Ashley Wooles

Abstract

Treatment of anhydrous FeX₂ (X = Cl, Br, I) with one equivalent of bis(diphenylphosphino)ethane (dppe) in refluxing THF afforded analytically pure white (X = Cl), light green (X = Br), and yellow (X = I) [FeX₂(dppe)]n (X = Cl, I; Br, II; I, III). Complexes I–III are excellent synthons from which to prepare a range of cyclopentadienyl derivatives. Specifically, treatment of I–III with alkali metal salts of C₅H₅ (Cp, series 1), C₅Me₅ (Cp*, series 2), C₅H₄SiMe₃ (Cp′, series 3), C₅H₃(SiMe₃)₂ (Cp′′, series 4), and C₅H₃(But)₂ (Cptt, series 5) afforded [Fe(Cp†)(Cl)(dppe)] 1Cl–5Cl, [Fe(Cp†)(Br)(dppe)] 1Br–5Br, and [Fe(Cp†)(I)(dppe)] 1I–5I (Cp† = Cp, Cp*, Cp′, Cp′′, or Cptt). Dissolution of 1I–5I in acetonitrile, or treatment of 1Cl–5Cl with Me₃SiI in acetonitrile (no halide exchange reactions were observed in other solvents) afforded the separated ion pair complexes [Fe(Cp†)(NCMe)(dppe)][I] 1SIP–5SIP. Attempts to reduce 1Cl–5Cl, 1Br–5Br, and 1I–5I with a variety of reductants (Li-Cs, KC₈, Na/Hg) were unsuccessful. Treatment of 1Cl–5Cl with LiAlH₄ gave the hydride derivatives [Fe(Cp†)(H)(dppe)] 1H–5H. This report provides a systematic account of reliable methods of preparing these complexes which may find utility in molecular wire and metal–metal bond chemistries. The complexes reported herein have been characterised by X-ray diffraction, NMR, IR, UV/Vis, and Mössbauer spectroscopies, cyclic voltammetry, density functional theory calculations, and elemental analyses, which have enabled us to elucidate the electronic structure of the complexes and probe the variation of iron redox properties as a function of varying the cyclopentadienyl or halide ligand.

Journal Article Type Article
Publication Date Jul 17, 2015
Journal Dalton transactions
Print ISSN 1477-9226
Electronic ISSN 1477-9234
Publisher Royal Society of Chemistry
Peer Reviewed Peer Reviewed
Volume 44
Issue 31
Pages 14159-14177
Institution Citation Evans, D. J., Liddle, S. T., Patel, D., Blake, A. J., Cornish, A. D., Davies, E. S., …Wooles, A. (2015). Synthesis and characterisation of halide, separated ion pair, and hydride cyclopentadienyl iron bis(diphenylphosphino)ethane derivatives. Dalton transactions : an international journal of inorganic chemistry / RSoC, 44(31), 14159-14177. https://doi.org/10.1039/c5dt00704f
DOI https://doi.org/10.1039/c5dt00704f
Keywords Halide; Ion pair; Hydride cyclopentadienyl iron bis(diphenylphosphino)ethane derivatives
Publisher URL http://pubs.rsc.org/en/Content/ArticleLanding/2015/DT/c5dt00704f#!divAbstract
Additional Information Authors' accepted manuscript of article published in: Dalton transactions, 2015, v.44, issue 31

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