Inorganic Chemistry, Institute of Chemistry and Biochemistry, Free University Berlin, 14195 Berlin, Germany.
Inorganic Chemistry, Department of Chemistry and Pharmacy, Friedrich-Alexander-University Erlangen-Nürnberg, 91058 Erlangen, Germany.
Science. 2016 Aug 12;353(6300):678-82. doi: 10.1126/science.aaf6362.
Ferrocene and its decamethyl derivative [Cp2Fe] are the most common standards for nonaqueous electrochemical investigations because of their well-defined and only mildly solvent-dependent reversible Fe(II)/Fe(III) redox couple. Higher oxidation states have only rarely been studied. We report the isolation and crystallographic and spectroscopic characterization of surprisingly stable Fe(IV) salts of the Cp*2Fe dication, produced by oxidation of [Cp2Fe] with AsF5, SbF5, or ReF6 in neat sulfur dioxide as well as XeF in neat hydrogen fluoride. The Sb2F11(-) salt exhibits a metallocene with the expected mutually parallel arrangements of the Cp* rings, whereas the As2F11(-), AsF6(-), SbF6(-), and ReF6(-) salts manifest tilt angles ranging from 4° to 17°. Both (57)Fe Mössbauer spectroscopy and superconducting quantum interference device magnetization studies reveal identical d-orbital splitting with an S = 1, (3)E ground state based on the 3d electronic configuration e2g (3)a1g (1) of all Cp*2Fe salts.
二茂铁及其十甲基衍生物 [Cp2Fe] 是最常用的非水电化学研究标准物质，因为它们具有定义明确且仅略微依赖于溶剂的可逆 Fe(II)/Fe(III) 氧化还原对。较高的氧化态很少被研究。我们报告了 Cp*2Fe 二阳离子的惊人稳定的 Fe(IV) 盐的分离、晶体学和光谱学表征，这些盐是通过 AsF5、SbF5 或 ReF6 在纯二氧化硫中以及在纯氟化氢中的 XeF 氧化 [Cp2Fe] 而产生的。Sb2F11(-) 盐表现出预期的 Cp* 环相互平行排列的茂金属，而 As2F11(-)、AsF6(-)、SbF6(-) 和 ReF6(-) 盐则表现出从 4°到 17°的倾斜角度。(57)Fe Mössbauer 光谱和超导量子干涉器件磁化研究都表明，所有 Cp*2Fe 盐都具有相同的 d 轨道分裂，基于 3d 电子构型 e2g(3)a1g(1)，具有 S = 1、(3)E 基态。
