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

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.

Citation

Evans, D. J., Liddle, S. T., Patel, D., Blake, A. J., Cornish, A. D., Davies, E. S., Lewis, W., McMaster, J., Steven, L., & 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, 44(31), 14159-14177. https://doi.org/10.1039/c5dt00704f

• Journal Article Type: Article
• Acceptance Date: Jul 7, 2015
• Online Publication Date: Jul 17, 2015
• Publication Date: Jul 17, 2015
• Deposit Date: Aug 11, 2015
• Publicly Available Date: Nov 23, 2017
• 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
• DOI: https://doi.org/10.1039/c5dt00704f
• Keywords: Halide; Ion pair; Hydride cyclopentadienyl iron bis(diphenylphosphino)ethane derivatives
• Public URL: https://hull-repository.worktribe.com/output/377625
• 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
• Contract Date: Nov 23, 2017