Homogeneous Catalytic Carbonylation of Nitroaromatics. 4. Preparation and Characterization of Ruthenium Radical Cations

Stephen J. Sherlock, David C. Boyd, Bahram Moasser, Wayne L Gladfelter

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Abstract

The neutral bis(phosphine) tricarbonyl complexes Ru(PR3)2(CO)3 (R = phenyl, benzyl, p-tolyl, cyclohexyl) and M[1,2-bis(diphenylphosphino)ethane](CO)3 (M = Ru, Fe) were found to undergo 1-electron oxidations giving the highly reactive 17-electron radical cations. The E1/2 values for the reversible oxidations of Ru(PR3)2(CO)3 were determined by using cyclic voltammetry and showed the expected dependence on phosphine basicity. Chemical oxidation of these complexes using ferrocenium salts generated species that were stable enough at -40 °C to characterize by using infrared and electron paramagnetic resonance spectroscopies. The infrared absorptions in the vCO region of a given cation appeared at least 100 cm-1 higher in energy compared to that of the neutral starting complex. The EPR spectra of the radical cations exhibited a broad 1:2:1 triplet with hyperfine coupling to phosphorus atoms of ≈20 G. Reagents such as organonitroso compounds, NO2, triphenylmethane, tri-n-butyltin hydride, methylene chloride, tri-n-butyltin chloride, and chloranil were found to react with the radical cations. The presence of the chelating ligand 1,2-bis(diphenylphosphino)ethane (dppe) made the neutral complex of either iron or ruthenium easier to oxidize and the corresponding radical cation far more reactive than the bis(phosphine) complexes. Evidence was found supporting the formation of the dimer [Ru(dppe)(CO)3]22+.

Original languageEnglish (US)
Pages (from-to)3626-3632
Number of pages7
JournalInorganic Chemistry
Volume30
Issue number19
DOIs
StatePublished - Sep 1 1991

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