174291-50-0Relevant articles and documents
Instability of the oxidation catalysts [OsIII(tpy)(bpy)(py)] 3+ and [OsIII(bpy)3]3+ in alkaline solution
Lebeau, Estelle L.
, p. 83 - 89 (2004)
The Os(III) complexes [OsIII(tpy)(bpy)(py)]3+ and [OsIII(bpy)3]3+ (bpy: 2,2′-bipyridine, py: pyridine, tpy: 2,2′,2″-terpyridine) are unstable toward self-reduction in alkaline solution. Product analysis performed by using UV-Vis spectroscopy, cyclic voltammetry, HPLC and GC show that ca. 90% of the reduced product that appears is the unmodified polypyridyl complex of Os(II), [Os II(tpy)(bpy)(py)]2+ or [OsII(bpy) 3]2+. The remaining 10% of the products are accounted for by other Os(II) complexes, including several which appear to have undergone varying degrees of ligand oxidation or substitution. Another product of the reduction of [OsIII(tpy)(bpy)(py)]3+ in basic solution has been identified as [OsII(tpy)(bpy)(OH2)]2+ which results from metal reduction and concomitant pyridine ligand loss. No O2 was detected as a product of the base-catalyzed self-reduction reaction. The Os(III) complexes are stable towards self-reduction and ligand loss in the dark in acetonitrile or aqueous solutions buffered below pH = 6. The rates observed for the self-reduction processes are sufficiently rapid at pH values above 7 that useful catalytic rate data cannot be obtained in basic solution unless the substrate of interest is sufficiently reactive and is present in large excess. Triple mixing, pH jump techniques have successfully been employed to observe reaction rates under strongly alkaline conditions.
Mechanistic implications of proton transfer coupled to electron transfer
Lebeau,Binstead,Meyer
, p. 10535 - 10544 (2007/10/03)
The kinetics of electron transfer for the reactions cis-[RuIV(bpy)2(py)(O)]2+ + H+ + [OsII(bpy)3]2+ ? cis-[RuIII(bpy)2(py)(OH)]2+ + [OsIII/
Electron-transfer reactions of manganese(II) and -(III) polyamino carboxylate complexes in aqueous media
Macartney, Donal H.,Thompson, David W.
, p. 2195 - 2199 (2008/10/08)
The kinetics of electron-transfer reactions involving the manganese(II) and -(III) complexes of ethylenediaminetetraacetate (edta4-) and trans-1,2-cyclohexanediaminetetraacetate (cdta4-) have been investigated in aqueous media. The cross-reactants employed in this study are osmium and cobalt tris(polypyridine) complexes, IrCl62-, and nickel polyaza complexes. The cross-reaction kinetic data have been correlated in terms of the Marcus relationship for outer-sphere electron-transfer reactions, and a self-exchange rate constant of 0.7 ± 0.4 M-1 s-1 was derived for the Mn(edta)(OH2)2-/- and Mn(cdta)(OH2)2-/- couples at 25°C. Deviations from this correlation were observed for the metal tris(polypyridine) complexes (reduced rate constants attributed to poor orbital overlap and hydrophobic/hydrophilic repulsions) and for a nickel(II) dioxime species, Ni(Hdiox)+ (enhanced reactivity related to a hydrogen-bonded precursor). The self-exchange rate constant is discussed in terms of the inner-sphere reorganization barriers to the exchange of an antibonding dσ* electron.
