Synthesis and Electrochemical Properties of Tetranuclear Di-μ-oxo-bis[di-μ-phenolatodiiron(III)] Complexes
作者：Yuji Miyazato、Masaaki Ohba、Hiroshi Sakiyama、Hisashi Ōkawa
DOI：10.1246/bcsj.80.1534
日期：2007.8.15
A series of tetrairon(III) complexes of di-μ-oxo-bis[di-μ-phenolatodiiron(III)] core, [Fe2(L)(L′)}2(μ-O)2](PF6)2 (1–11), where L2− is the phenol-based macrocyclic compartmental ligand and (L′)− is acetate, monochloroacetate, dichloroacetate, trifluoroacetate, pentafluoropropionate, benzoate, p-nitrobenzoate, pentafluorobenzoate, diethyl phosphate, diphenyl phosphate, or diethyldithiophosphate for 1–11, respectively, were synthesized. X-ray crystallographic studies for 4, 7, and 9 indicated that two Fe2(L)(L′)} units were connected by two oxo bridges to afford a tetranuclear di-μ-oxo-bis[di-μ-phenolatodiiron(III)] core. Cyclic voltammograms of 1–11 in acetonitrile showed a quasi-reversible or irreversible reduction wave between −332 and −620 mV (vs. Ag/Ag+), which were attributed to a two-electron process involving the Fe4III,III,III,III/Fe4II,II,III,III. The Fe4III,III,III,III/Fe4II,II,III,III potential shifted positive with a decrease in the electron-donating ability of the end-cap ligand, and a good linear correlation was found between the potentials and the pKa values of HL′. The Fe4II,II,III,III species were generated in acetonitrile by electrochemical reduction and showed broad intervalence transition bands in the range of 900–1500 nm.
一系列四铁(III)复合物，具有二-μ-氧-双[二-μ-酚酸亚铁(III)]核心，[Fe2(L)(L′)}2(μ-O)2](PF6)2 (1–11)，其中L2−为基于酚的宏环分隔配体，(L′)−分别为醋酸、单氯醋酸、二氯醋酸、三氟乙酸、五氟丙酸、苯酸、对硝基苯酸、五氟苯酸、二乙基磷酸酯、二苯磷酸酯或二乙基二硫酸盐。对于4、7和9的X射线晶体学研究表明，两个Fe2(L)(L′)}单元通过两个氧桥相连，从而形成四核二-μ-氧-双[二-μ-酚酸亚铁(III)]核心。在乙腈中，1–11的循环伏安图显示在−332到−620 mV（相对于Ag/Ag+）之间存在一个准可逆或不可逆的还原波，这归因于涉及Fe4III,III,III,III/Fe4II,II,III,III的两个电子过程。随着末端配体电子给予能力的减小，Fe4III,III,III,III/Fe4II,II,III,III的电位向正方向偏移，同时发现电位与HL′的pKa值之间存在良好的线性相关。在乙腈中通过电化学还原生成Fe4II,II,III,III物种，并在900-1500 nm范围内显示出宽泛的间接转移带。
