Khusniyarov Marat M, Bill Eckhard, Weyhermüller Thomas, Bothe Eberhard, Harms Klaus, Sundermeyer Jörg, Wieghardt Karl
Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany.
Chemistry. 2008;14(25):7608-22. doi: 10.1002/chem.200800546.
The four-coordinate iron complexes, [Fe(III)(pda(2-))(pda(.-))] (1) and AsPh(4)[Fe(II)(pda(2-))(2)] (2) were synthesized and fully characterized; pda(2-) is the closed-shell ligand N,N'-bis(pentafluorophenyl)-o-phenylenediamido(2-), and pda(.-) represents its one-electron-oxidized pi-radical anion. Single-crystal X-ray diffraction studies of 1 and 2 performed at 100(2) K reveal a distorted tetrahedral coordination environment at the iron centers, as a result of the intramolecular pi-pi interactions between C(6)F(5) rings. The electronic structures of 1 and 2 were unambiguously determined by a combination of (57)Fe Mössbauer and electronic spectroscopy, magnetic susceptibility measurements, X-ray crystallography, and DFT calculations. Compound 1 contains an intermediate-spin Fe(III) ion (S(Fe)=3/2) strongly antiferromagnetically coupled to a pi-ligand radical (S(R)=1/2) yielding an S(t)=1 ground state. Complex 2 possesses a high-spin Fe(II) center (S(Fe)=2) with two closed-shell dianionic ligands. Complexes 1 and 2 are members of the redox series Fe(pda)(2) with n=0 for 1 and n=2- for 2. The anion n=1- has been reported previously in the coordination salt [Fe(dad)(3)][Fe(pda)(2)] (3; dad=N,N'-bis(phenyl)-2,3-dimethyl-1,4-diaza-1,3-butadiene). A complicated temperature-dependent electronic structure has been observed for this salt. Here, DFT calculations performed on 3 confirm the previous assignments of spin- and oxidation-states. Thus, Fe(pda)(2) (n=0, 1-, 2-) constitutes an electron-transfer series, which has also been established by cyclic voltammetry; the mono- and dications (n=1+ and 2+) are also accessible in solution, but have not been further investigated. The (57)Fe Mössbauer spectra of Fe(pda)(2) species in 1 and 3 show extremely large quadrupole splitting constants due to addition of the valence and covalence contributions that have been confirmed by DFT calculations.
合成并全面表征了四配位铁配合物[Fe(III)(pda(2-))(pda(.-))] (1)和AsPh(4)[Fe(II)(pda(2-))(2)] (2)；pda(2-)是闭壳层配体N,N'-双(五氟苯基)-邻苯二胺基(2-)，pda(.-)代表其一电子氧化的π-自由基阴离子。在100(2) K下对1和2进行的单晶X射线衍射研究表明，由于C(6)F(5)环之间的分子内π-π相互作用，铁中心的配位环境呈扭曲的四面体。通过(57)Fe穆斯堡尔谱和电子光谱、磁化率测量、X射线晶体学以及密度泛函理论(DFT)计算相结合，明确确定了1和2的电子结构。化合物1包含一个中间自旋的Fe(III)离子(S(Fe)=3/2)，与一个π-配体自由基(S(R)=1/2)强烈反铁磁耦合，产生S(t)=1的基态。配合物2具有一个高自旋的Fe(II)中心(S(Fe)=2)和两个闭壳层二价阴离子配体。配合物1和2是氧化还原系列Fe(pda)(2)的成员，对于1，n = 0，对于2，n = 2-。阴离子n = 1-先前已在配位盐[Fe(dad)(3)][Fe(pda)(2)] (3；dad = N,N'-双(苯基)-2,3-二甲基-1,4-二氮杂-1,3-丁二烯)中报道。已观察到该盐具有复杂的温度依赖性电子结构。在此，对3进行的DFT计算证实了先前对自旋态和氧化态的归属。因此，Fe(pda)(2) (n = 0, 1-, 2-)构成一个电子转移系列，这也已通过循环伏安法得到证实；单阳离子和二阳离子(n = 1+和2+)在溶液中也可获得，但尚未进一步研究。1和3中Fe(pda)(2)物种的(57)Fe穆斯堡尔谱显示出极大的四极分裂常数，这是由于价态和共价贡献的加和，已通过DFT计算得到证实。
