Oxidized Styrylruthenium–Ferrocene Conjugates: From Valence Localization to Valence Tautomerism
Oxidized Styrylruthenium–Ferrocene Conjugates: From Valence Localization to Valence Tautomerism
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DOI：
10.1002/ejic.201600776
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发表时间：
2017-01
影响因子：
2.3
通讯作者：
Christopher Hassenrück;Philipp Mücke;Johanna Scheck;S. Demeshko;R. Winter
中科院分区：
文献类型：
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作者：
Christopher Hassenrück;Philipp Mücke;Johanna Scheck;S. Demeshko;R. Winter
我们报告了二茂铁基苯乙烯基钌缀合物 FcC6H4CH=CHRu(CO)(PiPr3)2(L)，其中钌烯基位点的电子密度通过共配体 L（L = Cl、acac、hfac 或 dpvm）的变化而改变。对三种衍生物的晶体学研究提供了围绕乙烯基-亚苯基和亚苯基-二茂铁基键旋转的构象自由度的快照。所有四种配合物都会经历两次连续的、可逆的单电子氧化，其电势取决于配体 L。根据红外光谱电化学，电子较少的氯和 hfac 配合物的第一次氧化强烈偏向二茂铁基位点。然而，acac复合物的自由基阳离子以两个平衡价互变异构体（VT）形式存在：Fc+C6H4CH=CH{Ruacac}Fc[C6H4CH=CH{Ruacac}]+ ({Ruacac = Ru(CO)(PiPr3)2(acac))，其中正电荷要么位于二茂铁基位点，要么离域在苯乙烯基钌部分上。变温 EPR 和穆斯堡尔光谱表明，二茂铁化合价互变异构体在低 T 下占主导地位。红外光谱中单独的 Ru(CO) 谱带的位置和相对强度的显着溶剂依赖性揭示了环境对两个 VT 相对稳定性的影响，而 acac 复合物的自由基阳离子的突出近红外谱带的强负溶剂化显色性则证明了潜在的激励。
We report on ferrocenyl styryl ruthenium conjugates FcC6H4CH=CHRu(CO)(PiPr3)2(L) where the electron density at the ruthenium alkenyl site is modified by the variation of coligand L (L = Cl, acac, hfac, or dpvm). Crystallographic studies on three derivatives provide snapshots of the conformational degrees of freedom for rotation around the vinyl-phenylene and the phenylene-ferrocenyl linkages. All four complexes undergo two consecutive, reversible one-electron oxidations, whose potentials depend on the ligand L. According to IR spectroelectrochemistry, the first oxidation of the less electron-rich chloro and hfac complexes is strongly biased towards the ferrocenyl site. The radical cation of the acac complex, however, exists as two equilibrating valence tautomers (VTs) Fc+C6H4CH=CH{Ruacac}Fc[C6H4CH=CH{Ruacac}]+ ({Ruacac = Ru(CO)(PiPr3)2(acac)), where the positive charge is either localized at the ferrocenyl site or delocalized over the styryl ruthenium moiety. Variable-temperature EPR and Mossbauer spectroscopy reveal that the ferrocenium valence tautomer dominates at low T. A marked solvent-dependence on the position and relative intensities of the separate Ru(CO) bands in the IR spectra reveals environmental effects on the relative stabilities of the two VTs, while the strong negative solvatochromism of the prominent near IR band of the radical cation of the acac complex argues for a sizable (intervalence) charge-transfer component of the underlying excitation.