Redox transformations of bis(2,2′-bipyridine)(1-methyl-1-pyridin-2- yl-ethylamine)ruthenium(II)

Justin Neill, Anna S. Nam, Kevin M. Barley, Benjamin Meza, David N. Blauch

Research output: Contribution to journalArticlepeer-review

Abstract

The amineruthenium(II) complex Ru(bpy)2(mpea)2+ has been prepared by the direct reaction of 1-methyl-1-pyridin-2-yl-ethylamine (mpea) with Ru(bpy)2Cl2 in ethanol/water and isolated as the hexafluorophosphate salt. Electrochemical analysis of this complex shows that it undergoes sequential one-electron oxidations to an amidoruthenium(III) intermediate (E°′ = 1.086 V vs NHE) and then to an amidoruthenium(IV) (E°′ = 0.928 V) or imidoruthenium(IV) (E°′ = 1.083 V) complex, depending upon the solution pH (pKa = 2.62 for the amidoruthenium(IV) species). At higher potentials (Epa = 1.5 V in 1.0 M H2SO4), the amido- or imidoruthenium(IV) species is irreversibly oxidized to the corresponding nitrosoruthenium(II) complex. The mechanism for this transformation appears, on the basis of b3lyp/cpcm/cep-31g(d) computations, to proceed through an imidoruthenium(V) intermediate, which is rapidly attacked by water to yield a Ru(II)-bound hydroxylamine radical, which is readily oxidized and deprotonated to produce the nitrosoruthenium(II) complex. The nitrosoruthenium(II) complex is quantitatively reduced to the original [Ru(bpy)2(mpea)]2+ complex at relatively negative potentials (Epc = -0.2 V in 1.0 M H2SO4).

Original languageEnglish (US)
Pages (from-to)5314-5323
Number of pages10
JournalInorganic Chemistry
Volume47
Issue number12
DOIs
StatePublished - Jun 16 2008
Externally publishedYes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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