A series of six tertiary-arsine-capped binuclear complexes, [L3Ru(µ-X)3RuL3][CF3SO3] (L = AsMe3, AsMe2Ph or AsMePh2; X = Cl or Br) together with a full range of purely PR3-capped analogues and the mixed-ligand complex [(Ph3P)(Me3As)2Ru(µ-Cl)3Ru(AsMe3)2(PPh3)][CF3SO3] have been characterised. The previously neglected arsine-capped compounds share the well defined electrochemical behaviour of their phosphine congeners. Stepwise reversible oxidations connect the Ru2II,II closed-shell d6d6 (=12-e) resting state with the d5d6 (11-e) and d5d5 (10-e) levels, and all the mixed-valence [L3Ru(µ-X)3RuL3]2+ species can be characterised through electrogeneration in CH2Cl2 at â60 °C. Unexpectedly, the Ru2II,III arsine complexes strongly resemble the classical ruthenium âbluesâ where L = NH3 or H2O. For such valence-delocalised systems the visible region ordinarily contains an intense Ï â Ï* band (the source of the intense blue colour) together with a much weaker, near-infrared δÏ* â Ï* band. Bonding within the RuX3Ru}2+ core can then be monitored directly by νÏâÏ*. The distinctly different spectral appearance of the more familiar PR3-capped mixed-valence compounds has been a long-standing puzzle, but the twenty electrogenerated 11-e binuclear systems assembled here with various AsR3 or PR3 terminal ligands are all delocalised, and clearly belong within a continuum of electronic behaviour with steadily decreasing metalâmetal interaction. In all, νÏâÏ* declines over a considerable range from 17 000 to below 5000 cmâ1, with the ligands ranked as follows: L = NH3 (and 1,4,7-trimethyl-1,4,7-triazacyclononane) > H2O > Cl, Br (i.e. nonahalides) > AsR3 > PR3 and µ-Cl > µ-Br. These changes are well correlated with systematic trends in the g⥠and g⥠components of the axial g tensor, and also with the gap between the stepwise oxidation potentials which shrinks from 1.2 to 0.45 V. For the PR3 complexes the decrease in νÏâÏ* is accompanied by progressive intensity transfer to the δÏ* â Ï* band. The anticipated Ru · · · Ru separation is of the order of 2.9 and 3.0 Ã
for the mixed-valence AsMe3/µ-Cl and PMe3/µ-Cl systems respectively, markedly longer than the crystallographic value of 2.75 Ã
in [(NH3)3Ru(µ-Cl)3Ru(NH3)3]2+. The geometric distinction between the AsR3- and PR3-capped dimers is an unexpected consequence of selective crowding between the substituent R groups and the µ-X3} array. The present Ru2II,III systems are electronically distinct from their PR3-containing osmium counterparts, such as [(Et3P)3Os(µ-Cl)3Os(PEt)3]2+, which show still greater visible/near-infrared spectral deviations.
一系列由次胂基封端的双核配合物, [L3Ru(µ-X)3RuL3][CF3SO3] (L = AsMe3, AsMe2Ph 或 AsMePh2; X = Cl 或 Br), 以及一系列纯由 PR3 封端的类似物和混合
配体配合物 [(Ph3P)(Me3As)2Ru(µ-Cl)3Ru(AsMe3)2(PPh3)][CF3SO3] 已被表征。之前被忽视的胂基封端配合物与他们的膦同类物具有良好的电
化学行为。分步可逆氧化过程将 Ru2II,II 闭壳层 d6d6 (=12-e) 基态与 d5d6 (11-e) 和 d5d5 (10-e) 能级连接起来, 所有混合价态的 [L3Ru(µ-X)3RuL3]2+ 物种都可以通过在
CH2Cl2 中于 -60 °C 下电
化学产生来表征。出乎意料的是, Ru2II,III 胂配合物与经典的
钌 "蓝" 配合物 (其中 L = NH3 或
H2O) 非常相似。对于这种价态离域的系统, 可见光区域通常包含一个强烈的 σ → σ* 带 (产生强烈的蓝色) 以及一个较弱的近红外 δπ* → σ* 带。 RuX3Ru}2+ 核心的键合可以通过 νσ-σ* 直接监测。更熟悉的 PR3 封端混合价态配合物的截然不同的光谱外观长期以来一直是一个谜, 但这里组装的二十个电
化学产生的 11-e 双核系统, 与各种 AsR3 或 PR3 终端
配体都是离域的, 并且显然属于电子行为的连续统,
金属-
金属相互作用逐渐减弱。所有 νσ-σ* 从 17000 到低于 5000 cm-1 都有明显的下降,
配体排序如下: L = NH3 (以及
1,4,7-三甲基-1,4,7-三氮杂环壬烷) > > Cl, Br (即非卤化物) > AsR3 > PR3 以及 µ-Cl > µ-Br。这些变化与轴向 g 张量的 g‖ 和 g⊥ 分量中的系统性趋势很好地相关, 并且与分步氧化电位的间隙从 1.2 缩小到 0.45 V 也很好地相关。对于 PR3 配合物, νσ-σ* 的减少伴随着逐渐向 δπ* → σ* 带的强度转移。预期的 Ru···Ru 分离大约为 2.9 和 3.0 Å 分别对应 AsMe3/µ-Cl 和 PMe3/µ-Cl 混合价态系统, 明显长于 [(NH3)3Ru(µ-Cl)3Ru(NH3)3]2+ 中的晶体学值 2.75 Å。 AsR3- 和 PR3- 封端的二聚体在几何上的区别是由于取代基 R 组和 µ-X3} 阵列之间的选择性拥挤产生的意外后果。当前的 Ru2II,III 系统在电子上与包含 PR3 的
锇同类物不同, 例如 [(Et3P)3Os(µ-Cl)3Os(PEt)3]2+, 它们在可见/近红外光谱上的偏差更大。