Electron delocalization in mixed-valence butadienediyl-bridged diruthenium complexes
Electron delocalization in mixed-valence butadienediyl-bridged diruthenium complexes
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DOI：
10.1007/s10008-005-0689-z
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发表时间：
2005-09
影响因子：
2.5
通讯作者：
J. Maurer;R. Winter;B. Sarkar;S. Záliš
中科院分区：
文献类型：
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作者：
J. Maurer;R. Winter;B. Sarkar;S. Záliš
本文报道了丁二烯二基桥接的二钌配合物[{Ru(PPh3)2(CO)Cl}2(μ-C4H4)](1)、[{Ru(PEt3)3(CO)Cl}2(μ-C4H4)](2)和[{Ru(PPh3)2(CO)Cl(NC5H4COOEt-4)}2(μ-C4H4)](3)的电化学和光谱电化学研究。所有这些配合物在两个连续的单电子步骤中被氧化，间隔315到680 mV，取决于共配体。第一种氧化是化学和电化学可逆的过程，而第二种氧化在室温下从几乎可逆变为不可逆。我们已经生成并研究了混合价态单位，并观察到CO波段漂移约25 cm−1，并且在约720至800和430至450 nm的可见区出现了新的波段。进入近红外的低能量带被指定为电荷共振（或价间电荷转移）吸收，并用于估计电子耦合参数hab。我们的研究指出2+的价态离域行为，以及1+和3+的近离域行为。然而，从溶液谱的耦合模式可以明显看出，即使是具有最小电位分裂的配合物，在较长的ESR时间尺度上也是完全离域的。在完全氧化和1+的超细分裂的情况下，IR波段的整体偏移表明了桥接c4h4配体上的电荷和自旋离域。利用DFT方法进行量子化学计算也解决了这个问题。在每个氧化水平下的几何优化揭示了C-C键模式的反转，从短-长-短转变为长-短-长变化，并且在指示阶段呈双碳（碳）结构。所有光谱特征，如红外波段位移，平均值和张量各向异性的计算完全再现。
We report electrochemical and spectroelectrochemical investigations on the butadienediyl-bridged diruthenium complexes [{Ru(PPh3)2(CO)Cl}2(μ-C4H4)] (1), [{Ru(PEt3)3(CO)Cl}2(μ-C4H4)] (2), and [{Ru(PPh3)2(CO)Cl(NC5H4COOEt-4)}2(μ-C4H4)] (3). All these complexes are oxidized in two consecutive one-electron steps separated by 315 to 680 mV, depending on the co-ligands. The first oxidation is a chemically and electrochemically reversible process whereas the second varies from nearly reversible to irreversible at room temperature. We have generated and investigated the mixed-valence monocations and observed CO band shifts of ca 25 cm−1and the appearance of new bands in the visible regime at ca 720 to 800 and 430 to 450 nm. The lower-energy band which tails into the near infrared has been assigned as a charge-resonance (or intervalence charge-transfer) absorption and used to estimate the electronic coupling parameterHAB. Our investigations point to valence delocalization for2+, and nearly delocalized behavior for1+and3+. Even the complex with the smallest potential splitting is, however, fully delocalized on the longer ESR timescale, as is evident from the coupling pattern of the solution spectrum. Overall IR band shifts on full oxidation and the hyperfine splittings for1+argue for charge and spin delocalization onto the bridging C4H4ligand. This issue has also been addressed by quantum chemical calculations employing DFT methods. Geometry optimizations at each oxidation level reveal inversion of the C–C bond pattern from a short–long–short to a long–short–long alteration and a bis(carbenic) structure at the dication stage. All spectroscopic features such as IR band shifts, averageg-values andg-tensor anisotropies are fully reproduced by the calculations.