Iron tricarbonyl α-diimine complexes: Synthesis, characterization, and electronic structure based on X-ray crystal structures
Iron tricarbonyl α-diimine complexes: Synthesis, characterization, and electronic structure based on X-ray crystal structures
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DOI：
10.1016/j.poly.2021.115168
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发表时间：
2021-04-30
期刊：
影响因子：
2.6
通讯作者：
Carroll, Maria E.
中科院分区：
文献类型：
--
作者：
Brown, Julia A.;Chaparro, Alexandra L.;Carroll, Maria E.
合成了一系列α-二亚胺三羰基铁配合物Fe（（Ar）DAB（Me））（CO）（3），其中α-二亚胺配体上的芳基取代基不同：（Ar）DAB（Me）= Ar-N=C（Me）-（Me）C=NAAr; 2aAr = C6 H5; 2bAr = 3，5-（CH 3）（2）C6 H3; 2cAr = 2，4，6-（CH 3）（3）C6 H2; 2d Ar = 3，5-Cl_2C_6H_3），并用H ~（-1）和C ~（-13）NMR对配合物进行了表征。化合物2a-d的红外光谱在2040 - 1950 cm（-1）之间显示出三个羰基伸缩峰，并且所有四种化合物都可以在-1.8--2.8 V vs.Cp2Fe/Cp 2Fe+之间被两个电子还原。nu（CO）和还原电位的差异与α-二亚胺芳基取代基的供电子能力的差异有关。通过单晶X射线衍射实验确定了化合物2a-d的结构，化合物2a、B和d具有畸变四方锥结构，而化合物2c具有畸变三角双锥结构。为了评估化合物2a-d中α-二亚胺配体的氧化态，我们合成并晶体学表征了一系列含有四种α-二亚胺配体的中性形式的化合物。在化合物2a-d中，平均C-N键长为1.332（1）埃，平均骨架C-C键长为1.403（2）埃，而在中性配体中分别为1.279（1）埃和1.520（3）埃。C-N键的延长和C-C键的缩短指示α-二亚胺配体的还原。因此，化合物2a-d最好描述为含有键合到自由基阴离子α-二亚胺配体的Fe（I）中心。(C)2021爱思唯尔有限公司保留所有权利。
A series of iron tricarbonyl alpha-diimine complexes, Fe((Ar)DAB(Me))(CO)(3), were synthesized, in which the identity of the aryl substituent on the alpha-diimine ligand was varied ((Ar)DAB(Me) = Ar-N=C(Me)-(Me)C=NAAr; 2a Ar = C6H5; 2b Ar = 3,5-(CH3)(2)C6H3; 2c Ar = 2,4,6-(CH3)(3)C6H2; 2d Ar = 3,5-Cl2C6H3), and the complexes were characterized by H-1 and C-13 NMR spectroscopy. The IR spectra of compounds 2a-d exhibit three carbonyl stretches between 2040 and 1950 cm(-1), and all four compounds can be reduced by two electrons at potentials between -1.8 and -2.8 V vs. Cp2Fe/Cp2Fe+. The differences in nu(CO) and reduction potentials are related to the differences in electron donating abilities of the alpha-diimine aryl substituents. The structures of 2a-d were determined by single crystal X-ray diffraction experiments; compounds 2a, b, and d have distorted square pyramidal structures, whereas, compound 2c is distorted trigonal bipyramidal. In order to assess the oxidation state of the alpha-diimine ligand in compounds 2a-d, we synthesized and crystallographically characterized a series of compounds that contain the neutral forms of the four alpha-diimine ligands. In compounds 2a-d, the average C-N bond lengths are 1.332(1) A and average backbone C-C bond lengths are 1.403(2) angstrom, compared to 1.279(1) angstrom and 1.520(3) angstrom, respectively, in the neutral ligands. The lengthening of the C-N bonds and shortening of the C-C bonds are indicative of reduction of the alpha-diimine ligands. Therefore, compounds 2a-d are best described as containing Fe(I) centers bonded to radical anionic alpha-diimine ligands. (C) 2021 Elsevier Ltd. All rights reserved.