Synthesis, characterisation and properties of ferrocenylalkylimidazolium salts

Nyamori, Vincent O.; Gumede, Mhleli; Bala, Muhammad D.

doi:10.1016/j.jorganchem.2010.01.019

Cited by 27 publications

(13 citation statements)

References 27 publications

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“…Compound 10 was isolated as oil, which could be due to a change in the size of the counter‐anion. It is well established that a good match in relative ionic size (cation‐to‐anion) is required for solidification and crystallization of ionic salts . Increasing the length of the alkyl chain on the imidazole from methyl to ethyl ( 12 and 8 ), did not significantly affect the melting point of the ferrocenylphenylimidazolium salts, but when the alkyl length was further lengthened to butyl a decrease in the melting point was observed, which is in agreement with reported literature data where it was attributed to increased degrees of freedom of the alkyl side chain R…”

Section: Resultssupporting

confidence: 90%

“…As a result, a lower electron density is experienced by the ferrocenyl centre, which makes oxidation relatively difficult. By using 1 H NMR chemical shifts, we have in the past probed the effect of increasing the size of the anion on the acidity of imidazole protons and found that, as the anionic size decreased, the chemical shifts of resonances in the 1 H NMR spectra shifted downfield . This confirmed that the size of the anion had an influence on electrostatic interactions between the imidazolium moiety and the ferrocenyl centre.…”

Section: Resultsmentioning

confidence: 81%

“…Syntheses of the two classes of salts reported herein, one containing a methylene and the other a phenyl group linking ferrocenyl to imidazolium moieties, were conducted via two different routes. The ferrocenylmethyleneimidazolium salts were synthesized following adaptation of our earlier reported procedure . In this procedure (Scheme ), ferrocenylmethyleneimidazole ( 2 ) was prepared from ferrocenylmethanol ( 1 ), which in turn was prepared by the reduction of ferrocenecarboxaldehyde with lithium aluminum hydride.…”

Section: Resultsmentioning

confidence: 99%

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Application of ferrocenylimidazolium salts as catalysts for the transfer hydrogenation of ketones

Ikhile

Bala

Nyamori

et al. 2013

Applied Organom Chemis

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Ferrocenylimidazolium salts with methylene and phenyl groups bridging the ferrocenyl and alkylimidazolium moieties were synthesized and characterized by spectroscopic and analytical methods. Crystal structures of two new compounds are also reported. Cyclic voltammetry was used to analyze the influence of the two bridging groups or spacers on electrochemical properties of the salts relative to the shifts in the formal electrode or peak potentials (E 0 or E 1/2 ) of the ferrocene/ferrocenium redox couple. Results from this study showed that all the salts exhibited higher electrode potentials relative to ferrocene, which is due to the electron-withdrawing effect of the imidazolium ion on the ferrocenyl moiety. Application of the salts as catalysts in transfer hydrogenation of ketones resulted in high conversion of saturated ketones to corresponding alcohols and turnover numbers as high as 1880. The catalysts were chemoselective towards reduction of the C ═ C bonds of conjugated 3-penten-2-one and 4-hexen-3-one to yield saturated ketones, while unconjugated 5-hexen-2-one was hydrogenated to an unsaturated alcohol.

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Section: Resultssupporting

confidence: 90%

Section: Resultsmentioning

confidence: 81%

Section: Resultsmentioning

confidence: 99%

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Application of ferrocenylimidazolium salts as catalysts for the transfer hydrogenation of ketones

Ikhile

Bala

Nyamori

et al. 2013

Applied Organom Chemis

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“…Thus, we synthesized 12a – i and 18a – o (Figure 1) as further alternatives. It should be mentioned that ferrocenyl‐alkylimidazolium salts with a methyl‐, butyl‐ and hexyl‐linker (see 18 with m = 1, 4, 6) between the ferrocenyl moiety and the imidazolium group have been reported by other groups 20b,20e,20g,29. However, in almost all cases, other counterions such as BF 4 – , PF 6 – , and SbF 6 – were used and the imidazole group was alkylated with a methyl‐, butyl‐, or octyl‐chain.…”

Section: Resultsmentioning

confidence: 93%

Synthesis and Characterization of New Ferrocene‐Containing Ionic Liquids

Gharib¹,

Hirsch²

2014

Eur J Org Chem

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A series of several new families of ferrocene‐containing imidazolium salts were synthesized by etherification of ferrocene methanol, acylation of ferrocene, and amide coupling of ferrocene carboxylic acid. The etherification was achieved by an acid‐catalyzed procedure and very good yields of between 86–93 % were obtained. Next to the nature of the linkage itself, the lengths of the alkyl chains linking the ferrocenyl moiety and the imidazolium group and the nature of the counterions were also varied. Interestingly, a γ‐effect can be observed for the ether compounds but this effect was only visible in 13C NMR spectroscopy. These new redox‐active ionic liquids were fully characterized by FTIR, 1H, 19F, and 13C NMR spectroscopy, and by MS, HRMS and elemental analysis.

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“…However, there are very few reports on electroactive ILs and there is a very narrow array of available structures and given that the design of a new RIL is hindered by a lack of knowledge of their structure-properties relationships [18][19][20][21][22][23][24]. In addition, the current library of RILs almost exclusively contains structures based on the modification of alkylimidazoliums, with some exceptions from reports on ferrocene-functionalized phosphonium IL [14,25] and metallocenium ILs [26,27].…”

Section: Introductionmentioning

confidence: 99%