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线性、富电子、同核稀土金属茂及其氧化还原活性。

Linear, Electron-Rich, Homoleptic Rare Earth Metallocene and Its Redox Activity.

机构信息

Department of Chemistry, Michigan State University, 578 South Shaw Lane, East Lansing, Michigan 48824, United States.

出版信息

Inorg Chem. 2023 Feb 6;62(5):2095-2104. doi: 10.1021/acs.inorgchem.2c03735. Epub 2023 Jan 23.

Abstract

The first homoleptic sandwich complex of dibenzocyclooctatetraene (dbCOT), representing a large cyclooctatetraene (COT) ligand with two fused benzene moieties, for any metal was accessed through salt metathesis of YCl with KdbCOT in the presence of 2.2.2-cryptand. Single-crystal X-ray diffraction analysis on red-brown [K(crypt-222)][Y(dbCOT)], , revealed a remarkably linear anionic yttrocene complex featuring a centroid-yttrium-centroid angle of 180.0°. The anionic moiety adopts a pseudo geometry, where the carbon atoms of the central COT ring exhibit a staggered geometry. In total, 36 π-electrons are stored on both dbCOT anions, rendering it the largest isolated sandwich complex containing only fused aromatic rings. The solution-state structure of was probed through a series of techniques involving cyclic voltammetry, UV-vis, and 1D and 2D nuclear magnetic resonance (NMR) spectroscopy, including Y NMR. The density functional theory (DFT) and natural bond orbital (NBO) analysis uncovered an ionic bonding interaction between the (dbCOT) ligands and Y ion. NICS calculations support the experimentally observed aromatic character of , despite the deviation from planarity found in the dbCOT moieties. The cyclic voltammograms allude to the accessibility of a radical oxidation state, dbCOT, based on a quasi-reversible feature. Excitingly, the chemical one-electron reduction of through exposure to potassium graphite yielded a paramagnetic molecule, which was detected by electron paramagnetic resonance (EPR) techniques. Notably, this EPR spectrum is the first one for any sandwich complex containing a COT radical. Remarkably, is thermally stable, and its isolation may provide access to mono- and multinuclear complexes comprising heavier metals with applications in small-molecule activation, single-molecule magnetism, and molecular nanowires.

摘要

首次获得了二苯并环辛四烯(dbCOT)的首个同配位夹心配合物,该配合物代表了一种带有两个稠合苯环的大环辛四烯(COT)配体,所用金属为 Y 盐通过与 KdbCOT 的盐交换反应制得,反应在 2.2.2-穴醚存在的条件下进行。单晶 X 射线衍射分析显示,红色-棕色[K(crypt-222)][Y(dbCOT)],为一个具有显著线性的镱阳离子配合物,其中心离子-镱-中心离子夹角为 180.0°。阴离子部分采用拟 sp2 杂化轨道,其中中心 COT 环上的碳原子呈现交错式几何构型。总的来说,两个 dbCOT 阴离子共储存了 36 个 π 电子,使其成为仅含有稠合芳环的最大孤立夹心配合物。通过一系列技术(包括循环伏安法、紫外-可见光谱法以及一维和二维核磁共振(NMR)光谱法,包括 Y NMR)探测了[K(crypt-222)][Y(dbCOT)]在溶液状态下的结构。密度泛函理论(DFT)和自然键轨道(NBO)分析揭示了(dbCOT)配体与 Y 离子之间存在离子键相互作用。NICS 计算支持了尽管在 dbCOT 部分发现了偏离平面的情况,但该配合物具有实验观测到的芳香性。循环伏安图暗示了基于准可逆特征,可能存在自由基氧化态 dbCOT。令人兴奋的是,通过暴露于钾石墨使[K(crypt-222)][Y(dbCOT)]发生化学单电子还原,得到了顺磁性分子,这可以通过电子顺磁共振(EPR)技术检测到。值得注意的是,这是第一个具有 COT 自由基的夹心配合物的 EPR 谱。此外,[K(crypt-222)][Y(dbCOT)]具有热稳定性,其分离可能为包含较重金属的单核和多核配合物的制备提供了途径,这些配合物可应用于小分子活化、单分子磁体和分子纳米线等领域。

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