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

INOR 604

David Blauch, dablauch@davidson.edu1, Justin Neill, jln9m@cms.mail.virginia.edu2, Anna Nam, annam@davidson.edu1, Kevin M. Barley, bobarley@davidson.edu1, and Benjamin Meza, mezabp@vcu.edu3. (1) Department of Chemistry, Davidson College, Box 7120, Davidson, NC 28035, (2) Department of Chemistry, University of Virginia, Charlottesville, VA 22904, (3) Virginia Commonwealth University, Richmond, VA 23284
The amineruthenium(II) complex Ru(bpy)2(mpea)2+ has been prepared by 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 it undergoes sequential one-electron oxidations to an amidoruthenium(III) intermediate (Eo' = 1.086 V vs NHE) and then an amidoruthenium(IV) (Eo' = 0.928 V) or imidoruthenium(IV) (Eo' = 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 attacked by water to yield a RuIII-N-OH2 species that is readily oxidized and deprotonated to yield the nitrosoruthenium(II) product. Cyclic voltammetry, coulometry, and UV-vis spectroscopy show the nitrosoruthenium(II) complex is quantitatively reduced to the starting Ru(bpy)2(mpea)2+ at relatively negative potentials (Epc = -0.2 V in 1.0 M H2SO4).
 

Inorganic Electrochemistry
7:00 PM-10:00 PM, Tuesday, August 21, 2007 BCEC -- Exhibit Hall - B2, Poster

Division of Inorganic Chemistry

The 234th ACS National Meeting, Boston, MA, August 19-23, 2007