Electrooxidation of [(η5-C5H5)Fe(CO)2]2 as a probe of the nucleophilic properties of ionic liquid anions

Torriero, Angel A. J., Shiddiky, Muhammad J. A., Bullock, John P., Boas, John F., MacFarlane, Douglas R. and Bond, Alan M. 2010, Electrooxidation of [(η5-C5H5)Fe(CO)2]2 as a probe of the nucleophilic properties of ionic liquid anions, Inorganic chemistry, vol. 49, no. 5, pp. 2502-2511, doi: 10.1021/ic9025238.

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Title Electrooxidation of [(η5-C5H5)Fe(CO)2]2 as a probe of the nucleophilic properties of ionic liquid anions
Author(s) Torriero, Angel A. J.ORCID iD for Torriero, Angel A. J. orcid.org/0000-0001-8616-365X
Shiddiky, Muhammad J. A.
Bullock, John P.
Boas, John F.
MacFarlane, Douglas R.
Bond, Alan M.
Journal name Inorganic chemistry
Volume number 49
Issue number 5
Start page 2502
End page 2511
Total pages 10
Publisher American Chemical Society
Place of publication San Diego, Calif.
Publication date 2010-02-01
ISSN 0020-1669
Summary The oxidative electrochemistry of [CpFe(CO)2]2, 1 (Cp = [η5-C5H5]–), was examined in detail in ionic liquids (ILs) composed of ions of widely varying Lewis acid−base properties. Cyclic voltammetric responses were strongly dependent on the nucleophilic properties of the IL anion, but all observations are consistent with the initial formation of 1+ followed by attack from the IL anion. In [NTf2]–-based ILs ([NTf2]– = bis(trifluoromethylsulfonyl)amide), the process shows nearly ideal chemical reversibility as the reaction between 1+ and [NTf2]– is very slow. This is highly significant, as 1+ is known to be highly susceptible to nucleophilic attack and its stability indicates a remarkable lack of coordinating ability of these ILs. In 1-methyl-3-butylimidazolium hexafluorophosphate, [bmim][PF6], the oxidation of 1 is still largely reversible, but there is more pronounced evidence of [PF6]– coordination. In contrast, 1 exhibits an irreversible two-electron oxidation process in a dicyanamide-based IL. This overall oxidation process is thought to proceed via an ECE mechanism, details of which are presented. Rate constants were estimated by fitting the experimental data to digital simulations of the proposed mechanism. The use of [NTf2]–-based ILs as a supporting electrolyte in CH2Cl2 was examined by using this solvent/electrolyte as a medium in which to perform bulk electrolyses of 1 and 1*, the permethylated analogue [Cp*Fe(CO)2]2 (Cp* = [η5-C5(CH3)5]–). These cleanly yielded the corresponding binuclear radical-cation species, 1+ and 1*+, which were subsequently characterized by electron paramagnetic resonance (EPR) spectroscopy. In addition to the above oxidation studies, the reduction of 1 was studied in each of the ILs; differences in cathodic peak potentials are attributed, in part, to ion-pairing effects. This study illustrates the wide range of electrochemical environments available with ILs and demonstrates their utility for the investigation of the redox properties of metal carbonyls and other organometallic compounds.
Language eng
DOI 10.1021/ic9025238
Field of Research 030604 Electrochemistry
030102 Electroanalytical Chemistry
Socio Economic Objective 970103 Expanding Knowledge in the Chemical Sciences
HERDC Research category C1.1 Refereed article in a scholarly journal
Copyright notice ©2010, American Chemical Society
Persistent URL http://hdl.handle.net/10536/DRO/DU:30038943

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