Electrochemical-Electron Spin Resonance Investigation of Reactions of 17-Electron Iron Carbonyl Radical Cation Complexes

R. N. Bagchi, A. M. Bond, C. L. Heggie, T. L. Henderson, E. Mocellin, R. A. Seikel

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Abstract

In situ electrochemical oxidation of Fe(CO)3(PPh3)2 in dichloromethane in the cavity of an electron spin resonance (ESR) spectrometer, having variable-temperature capabilities and a microprocessor-based data acquisition system, enables the formation and decay of the 17-electron cation radical [Fe(CO)3(PPh3)2]+ to be studied. Electrolysis at platinum electrodes shows that [Fe(CO)3(PPh3)2]+ is relatively stable in noncoordinating solvents in the absence of oxygen and light. At silver and mercury electrodes, [Fe(CO)3(PPh3)2]+, while also being the stable product of electrolysis, is generated via silver and mercury intermediates, which are also light sensitive. [Fe(CO)3(PPh3)2]+ reacts with acetone (or acetonitrile) in a second-order process to produce transient solvent-substituted cation radical species that participate in a series of reactions to produce Fe(CO)3(PPh3)2 and iron(II) compounds. These reactions appear to parallel those reported previously with anionic ligands. The reaction of [Fe(CO)3(PPh3)2]+ with PPh3, AsPh3, SbPh3, Fe(CO)4PPh3, Fe(CO)3(AsPh3)2, Fe(CO)4AsPh3, Fe-(CO)3(SbPh3)2, or Fe(CO)4SbPh3 in dichloromethane is stoichiometric and rapid, producing Fe(CO)3(PPh3)2 and other species. Evidence for dimer formation as an intermediate is inferred from the ESR data with some of these reactions. Subsequent radical and molecular reactions lead to identification of Fe(CO)3(PPh3)2Cl at -35 °C, with chloride being obtained from the solvent dichloromethane.

Original languageEnglish
Pages (from-to)3007-3012
Number of pages6
JournalInorganic Chemistry
Volume22
Issue number21
DOIs
Publication statusPublished - Oct 1983
Externally publishedYes

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