The di- and trinuclear ferrocene species Li[Fc-BPh2-Fc] (Li[9]) and Li2[Fc-BPh2-fc-BPh2-Fc] (Li2[10]) have been investigated with regard to their electrochemical properties and the degree of intervalence charge-transfer after partial oxidation. Li[9] shows two distinct one-electron redox waves for its chemically equivalent ferrocenyl substituents in the cyclic voltammogram (E1/2 = −0.38 V, −0.64 V; vs. FcH/FcH+). The corresponding values of Li2[10] are E1/2 = −0.45 V (two-electron process) and −1.18 V. All these redox events are reversible at r. t. on the time scale of cyclic voltammetry. X-ray crystallography on the mixed-valent FeII2FeIII complex Li(12-c-4)2[10] reveals the centroid–centroid distance between the cyclopentadienyl rings of each of the terminal ferrocenyl substituents (3.329 Å) to be significantly smaller than in the central 1,1′-ferrocenediyl fragment (3.420 Å). This points towards a charge-localized structure (on the time scale of X-ray crystallography) with the central iron atom being in the FeIII state. Mößbauer spectroscopic measurements on Li(12-c-4)2[10] lend further support to this interpretation. Spectroelectrochemical measurements on Li[9] and Li2[10] in the wavelength range between 300–2800 nm do not show bands interpretable as intervalence charge-transfer absorptions for the mixed-valent states. All data accumulated so far lead to the conclusion that electronic interaction between the individual Fe atoms in Li[9] and Li2[10] occurs via a through-space pathway and/or is electrostatic in nature.
研究人员对
二茂铁的二核和三核物种 Li[Fc-BPh2-Fc] (Li[9])和 Li2[Fc-BPh2-fc-BPh2-Fc] (Li2[10])进行了研究,探讨了它们的电
化学特性以及部分氧化后的间隔电荷转移程度。在循环伏安图中,Li[9] 的
化学等价
二茂铁取代基显示出两个不同的单电子氧化还原波(E1/2 = -0.38 V,-0.64 V;vs. FcH/FcH+)。Li2[10] 的相应值为 E1/2 = -0.45 V(双电子过程)和-1.18 V。所有这些氧化还原事件在循环伏安时间尺度上都是可逆的。混合价 FeII2FeIII 复合物 Li(12-c-4)2[10] 的 X 射线晶体学显示,每个末端
二茂铁取代基的
环戊二烯环之间的中心距(3.329 Å)明显小于中心 1,1′-
二茂铁片段的中心距(3.420 Å)。这表明该物质具有电荷定位结构(在 X 射线晶体学的时间尺度上),中心
铁原子处于 FeIII 态。对 Li(12-c-4)2[10] 的莫氏鲍尔光谱测量进一步支持了这一解释。在 300-2800 纳米波长范围内对 Li[9] 和 Li2[10] 进行的分光电
化学测量并未显示可解释为混合价态的间隔电荷转移吸收带。迄今为止积累的所有数据都表明,Li[9] 和 Li2[10] 中单个
铁原子之间的电子相互作用是通过空间途径和/或静电性质发生的。