Coordination and Redox Chemistry of Substituted-Polypyridyl Complexes of Ruthenium
- 1 January 1996
- journal article
- Published by American Chemical Society (ACS) in Inorganic Chemistry
- Vol. 35 (14) , 4120-4127
- https://doi.org/10.1021/ic9512587
Abstract
The complexes [Ru(tpy)(acac)(Cl)], [Ru(tpy)(acac)(H2O)](PF6) (tpy = 2,2‘,2‘‘-terpyridine, acacH = 2,4 pentanedione) [Ru(tpy)(C2O4)(H2O)] (C2O42- = oxalato dianion), [Ru(tpy)(dppene)(Cl)](PF6) (dppene = cis-1,2-bis(diphenylphosphino)ethylene), [Ru(tpy)(dppene)(H2O)](PF6)2, [Ru(tpy)(C2O4)(py)], [Ru(tpy)(acac)(py)](ClO4), [Ru(tpy)(acac)(NO2)], [Ru(tpy)(acac)(NO)](PF6)2, and [Ru(tpy)(PSCS)Cl] (PSCS = 1-pyrrolidinedithiocarbamate anion) have been prepared and characterized by cyclic voltammetry and UV−visible and FTIR spectroscopy. [Ru(tpy)(acac)(NO2)]+ is stable with respect to oxidation of coordinated NO2- on the cyclic voltammetric time scale. The nitrosyl [Ru(tpy)(acac)(NO)]2+ falls on an earlier correlation between ν(NO) (1914 cm-1 in KBr) and E1/2 for the first nitrosyl-based reduction 0.02 V vs SSCE. Oxalate ligand is lost from [RuII(tpy)(C2O4)(H2O)] to give [Ru(tpy)(H2O)3]2+. The Ru(III/II) and Ru(IV/III) couples of the aqua complexes are pH dependent. At pH 7.0, E1/2 values are 0.43 V vs NHE for [RuIII(tpy)(acac)(OH)]+/[RuII(tpy)(acac)(H2O)]+, 0.80 V for [RuIV(tpy)(acac)(O)]+/[RuIII(tpy)(acac)(OH)]+, 0.16 V for [RuIII(tpy)(C2O4)(OH)]/[RuII(tpy)(C2O4)(H2O)], and 0.45 V for [RuIV(tpy)(C2O4)(O)]/[RuIII(tpy)(C2O4)(OH)]. Plots of E1/2 vs pH define regions of stability for the various oxidation states and the pKa values of aqua and hydroxo forms. These measurements reveal that C2O42- and acac- are electron donating to RuIII relative to bpy. Comparisons with redox potentials for 21 related polypyridyl couples reveal the influence of ligand changes on the potentials of the Ru(IV/III) and Ru(III/II) couples and the difference between them, ΔE1/2. The majority of the effect appears in the Ru(III/II) couple. A linear correlation exists between ΔE1/2 and the sum of a set of ligand parameters defined by Lever et al., ΣEi(Li), for the series of complexes, but there is a dramatic change in slope at ΔE1/2 ≈ −0.11 V and ΣEi(Li) = 1.06 V. Extrapolation of the plot of ΔE1/2 vs ΣEi(Li) suggests that there may be ligand environments in which Ru(III) is unstable with respect to disproportionation into Ru(IV) and Ru(II). This would make the two-electron RuIVO/RuIIOH2 couple more strongly oxidizing than the one-electron RuIVO/RuIIIOH couple.Keywords
This publication has 46 references indexed in Scilit:
- Redox and spectral properties of the four-electron oxidant trans-aquadioxo(terpyridine)ruthenium(2+) diperchlorateInorganic Chemistry, 1992
- Oxidation of hydroquinones by ruthenium complexes [(bpy)2(py)RuIV(O)]2+ and [(bpy)2(py)RuIII(OH)]2+. Proton-coupled electron transferJournal of the American Chemical Society, 1992
- Cyclometallation ofN, N-dimethyl-3-furancarbothioamide with palladium(II), platinum(II), ruthenium(II) and rhodium(III)Transition Metal Chemistry, 1990
- The synthesis, characterization, and reactivity of a novel nitroruthenium(III) complexJournal of the American Chemical Society, 1988
- First synthesis of a nitro complex of ruthenium(III), as a key intermediate in the oxidation of nitro ligand to give both nitrosyl and nitrato ligandsInorganic Chemistry, 1986
- Instability of the oxidation catalysts ([(bpy)2(py)Ru(O)]2+) and oxo(1,10-phenanthroline)(2,2',2"-terpyridine) ruthenium(2+) ([(trpy)(phen)Ru(O)]2+) in basic solutionInorganic Chemistry, 1985
- Kinetics and mechanism of oxidation of aromatic hydrocarbons by Ru(trpy)(bpy)O2+Journal of the American Chemical Society, 1982
- Oxidation of the ligand in nitro complexes of ruthenium(III)Inorganic Chemistry, 1980
- Reversible electron transfer in ruthenium nitrosyl complexesInorganic Chemistry, 1977
- New complexes of ruthenium(II) with triphenylphosphine and other ligandsJ. Chem. Soc. A, 1969