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Anodic Electrochemistry of Multiferrocenyl Phosphine and Phosphine Chalcogenide Complexes in Weakly Nucleophilic Electrolytes
journal contribution
posted on 2005-01-03, 00:00 authored by Frédéric Barrière, Rein U. Kirss, William E. GeigerThe anodic electrochemistry of several compounds containing two or three ferrocenyl
moieties linked by a phosphine or phosphine chalcogenide group has been studied in
dichloromethane containing [NBu4][TFAB], where TFAB is the tetrakis(perfluoroaryl)borate
anion, [B(C6F5)4]-. In two cases, namely [CpFe(C5H4)]3P (3) and [CpFe(C5H4)]2PO(Ph) (6),
the first one-electron-oxidation product is stable on the cyclic voltammetric (CV) time scale
and subsequent oxidations at more positive potentials are also observed. The oxidations of
[CpFe(C5H4)]2PPh (2) and [CpFe(C5H4)]3PSe (7) are not reversible, and their monocations
undergo follow-up reactions that are first-order and second-order, respectively, in the neutral
compound. The results are consistent with a model in which the initial oxidation always
involves a largely ferrocenyl-based HOMO which, nevertheless, has significant phosphine
or phosphine chalcogenide character, allowing radical-type reactions, including dimerizations,
at the linking group. The traditional nonaqueous supporting electrolyte anions such as [PF6]-
and [BF4]- are shown to be responsible for many of the earlier difficulties in interpreting
the anodic electrochemistry of this oft-studied class of compounds.