Coordination and redox chemistry of substituted-polypyridyl complexes of ruthenium
Coordination and redox chemistry of substituted-polypyridyl complexes of ruthenium
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DOI：
10.1021/ic9512587
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发表时间：
1996-07-03
影响因子：
4.6
通讯作者：
Meyer, TJ
中科院分区：
文献类型：
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作者：
Dovletoglou, A;Adeyemi, SA;Meyer, TJ
[Ru（tpy）（acac）（Cl）]，[Ru（tpy）（acac）（H_2O）]（PF_6）（tpy = 2，2 '，2“-三联吡啶，acacH = 2，4戊二酮）[Ru（tpy）（C2 O 4）（H2O）]（C2 O 42- =二价阴离子），[Ru（tpy）（dppene）（Cl）]（PF 6）（dppene = cis-1，2-bis（diphenylphosphino）ethylene），[Ru（tpy）（dppene）（H2O）]（PF 6）（2），[Ru（tpy）（C2O4）（py）]，[Ru（tpy）（acac）（py）]（ClO4），[Ru（tpy）（acac）（NO2）]，合成了[Ru（tpy）（acac）（NO）]（PF_6）（2）和[Ru（tpy）（PSCS）Cl]（PSCS = 1-吡咯烷二硫代氨基甲酸根阴离子），并用循环伏安法、红外光谱和紫外可见光谱对其进行了表征。[Ru（tpy）（acac）（NO2）]（+）在循环伏安时间标度上相对于配位NO2-的氧化是稳定的。亚硝酰基[Ru（tpy）（acac）（NO）]（2+）福尔斯落在较早的v（NO）（1914 cm（-1）在KBr中）和E（1/2）之间的相关性上，对于第一次基于亚硝酰基的还原0.02 V vs SSCE。草酸根配体从[Ru-II（tpy）（C2 O 4）（H2O）]中失去，得到[Ru（tpy）（H2O）（3）]（2+）。水溶液配合物的Ru（III/II）和Ru（IV/III）对具有pH依赖性。在pH 7.0时，[Ru-III（tpy）（acac）（OH）]（+）/[Ru-II（tpy）（acac）（H2O）]（+）的E（1/2）值为0.43 V，[Ru-IV（tpy）-（acac）（O）]（+）/[Ru-III（tpy）（acac）（OH）]（+）的E（1/2）值为0.80 V，[Ru-III（tpy）（C2O4）（OH）]/[Ru-II（tpy）（C2O4）（H2O）]为0.16 V，[Ru-IV（tpy）（C2O4）（O）]/[Ru-III（tpy）（C2O4）（OH）]为0.45 V。E（1/2）与PH的曲线图定义了各种氧化态的稳定区域以及水和羟基形式的pK（a）值。这些测量结果表明，C2 O 42-和acac（-）是电子给Ru-III相对于bpy。与21个相关的聚吡啶对的氧化还原电位的比较揭示了配体变化对Ru（IV/III）和Ru（III/II）对的电位的影响以及它们之间的差异，Δ E（1/2）。大部分的影响出现在Ru（III/II）对。Δ E（1/2）与Lever等人定义的一组配体参数之和之间存在线性相关，Σ E（i）（L（i）），对于络合物系列，但在Δ E（1/2）接近-0.11 V和σ E（i）（L（i））= 1.06 V处斜率有显著变化。Δ E（1/2）VS σ E（i）（L（i））曲线的外推表明，可能存在Ru（III）相对于还原成Ru（IV）不稳定的配体环境。和Ru（II）。这将使双电子RuIVO/（RuOH 2）-O-II电对比单电子（RuO）-O-IV/（RuOH）-O-III电对更强地氧化。
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 W-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 v(NO) (1914 cm(-1) in KBr) and E(1/2) for the first nitrosyl-based reduction 0.02 V vs SSCE. Oxalate ligand is lost from [Ru-II(tpy)(C2O4)(H2O)] to give [Ru(tpy)(H2O)(3)](2+). The Ru(III/Il) and Ru(IV/III) couples of the aqua complexes are pH dependent. At pH 7.0, E(1/2) values are 0.43 V vs NHE for [Ru-III(tpy)(acac)(OH)](+)/[Ru-II(tpy)(acac)(H2O)](+), 0.80 V for [Ru-IV(tpy)-(acac)(O)](+)/[Ru-III(tpy)(acac)(OH)](+), 0.16 V for [Ru-III(tpy)(C2O4)(OH)]/[Ru-II(tpy)(C2O4)(H2O)] and 0.45 V for [Ru-IV(tpy)(C2O4)(O)]/[Ru-III(tpy)(C2O4)(OH)]. Plots of E(1/2) vs PH define regions of stability for the various oxidation states and the pK(a) values of aqua and hydroxo forms. These measurements reveal that C2O42- and acac(-) are electron donating to Ru-III 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, Delta E(1/2). The majority of the effect appears in the Ru(III/II) couple. A linear correlation exists between Delta E(1/2) and the sum of a set of ligand parameters defined by Lever et al., Sigma E(i)(L(i)), for the series of complexes, but there is a dramatic change in slope at Delta E(1/2) approximate to -0.11 V and Sigma E(i)(L(i)) = 1.06 V. Extrapolation of the plot of Delta E(1/2) VS Sigma E(i)(L(i)) 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/(RuOH2)-O-II couple more strongly oxidizing than the one-electron (RuO)-O-IV/(RuOH)-O-III couple.