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)(2)Cl-2 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 degrees ' = 1.086 V vs NHE) and then to an amidoruthenium(IV) (E degrees ' = 0.928 V) or imidoruthenium(IV) (E degrees ' = 1.083 V) complex, depending upon the solution pH (pK(a) = 2.62 for the amidoruthenium(IV) species). At higher potentials (E-pa = 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 (E-pc = -0.2 V in 1.0 M H2SO4).