Halide-bridged arsine- and phosphine-capped diruthenium complexes, [(R3As)3Ru(µ-X)3Ru(AsR3)3]+ and [(R3P)3Ru(µ-X)3Ru(PR3)3]+ (X = Cl or Br), as precursors to confacial mixed-valence ruthenium ‘blues’: spectroelectrochemical studies spanning the binuclear oxidation states II,II, II,III and III,III
Halide-bridged arsine- and phosphine-capped diruthenium complexes, [(R3As)3Ru(µ-X)3Ru(AsR3)3]+ and [(R3P)3Ru(µ-X)3Ru(PR3)3]+ (X = Cl or Br), as precursors to confacial mixed-valence ruthenium ‘blues’: spectroelectrochemical studies spanning the binuclear oxidation states II,II, II,III and III,III
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DOI：
10.1039/a705675c
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发表时间：
1997
期刊：
影响因子：
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通讯作者：
B. Yeomans;D. Humphrey;G. Heath
中科院分区：
文献类型：
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作者：
B. Yeomans;D. Humphrey;G. Heath
研究了一系列六种叔arsin包封的双核配合物[L3Ru（µ-X）3RuL3][CF3SO3] (L = AsMe3， AsMe2Ph或AsMePh2； X = Cl或Br)，以及一系列纯pr3包封的类似物和混合配体配合物[(Ph3P)(Me3As)2Ru（µ-Cl）3Ru(AsMe3)2(PPh3)][CF3SO3]。先前被忽视的砷封顶化合物与它们的磷化氢同系物有着明确的电化学行为。逐步可逆氧化将Ru2II、II闭合壳d6d6 （=12-e）的静息态与d5d6 （11-e）和d5d5 （10-e）的能级连接起来，所有的混价[L3Ru（µ-X）3RuL3]2+可以通过在CH2Cl2中在-60℃下的电生成来表征。出乎意料的是，Ru2II，III砷配合物与L = NH3或H2O的经典钌“蓝”非常相似。对于这样的价离域系统，可见光区通常包含一个强烈的σ→σ*波段（强烈蓝色的来源）和一个更弱的近红外δπ*→σ*波段。然后可以用νσ→σ*直接监测{RuX3Ru}2+芯内的键合。我们更熟悉的PR3盖顶的混合价化合物的明显不同的光谱外观一直是一个长期存在的难题，但是这里组装的20个电生成的11-e双核系统具有各种AsR3或PR3末端配体，它们都是离域的，并且显然属于一个连续的电子行为，金属-金属相互作用稳步减少。总的来说，νσ→σ*在17000 cm-1到5000 cm-1以下的相当大范围内下降，配体的排列顺序如下：L = NH3（和1,4,7-三甲基-1,4,7-三氮杂环壬烷）> H2O > Cl, Br（即非卤化物）> AsR3 > PR3和µ-Cl >µ-Br。这些变化与轴向g张量的g∥和g⊥分量的系统趋势密切相关，也与从1.2 V缩小到0.45 V的逐步氧化电位之间的差距密切相关。对于PR3配合物，νσ→σ*的减小伴随着强度向δπ*→σ*波段的逐渐转移。混合价AsMe3/µ-Cl和PMe3/µ-Cl体系的Ru··Ru分离值分别为2.9和3.0 A，明显高于[(NH3)3Ru（µ-Cl）3Ru(NH3)3]2+的结晶值2.75 A。AsR3-和pr3 -二聚体之间的几何差异是取代基R基团和{µ- x3}阵列之间选择性拥挤的意外结果。目前的Ru2II，III体系在电子上与含有pr3的锇体系不同，例如[(Et3P)3Os（µ-Cl）3Os(PEt)3]2+，后者显示出更大的可见/近红外光谱偏差。
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 –60 °C. Unexpectedly, the Ru2II,III arsine complexes strongly resemble the classical ruthenium ‘blues’ where L = NH3 or H2O. For such valence-delocalised systems the visible region ordinarily contains an intense σ → σ* band (the source of the intense blue colour) together with a much weaker, near-infrared δπ* → σ* band. Bonding within the {RuX3Ru}2+ core can then be monitored directly by νσ→σ*. 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 metal–metal interaction. In all, νσ→σ* declines over a considerable range from 17 000 to below 5000 cm–1, 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 νσ→σ* is accompanied by progressive intensity transfer to the δπ* → σ* band. The anticipated Ru · · · Ru separation is of the order of 2.9 and 3.0 A for the mixed-valence AsMe3/µ-Cl and PMe3/µ-Cl systems respectively, markedly longer than the crystallographic value of 2.75 A 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.