Electronic Structure and Magnetic Properties of a Titanium(II) Coordination Complex
Electronic Structure and Magnetic Properties of a Titanium(II) Coordination Complex
复制标题
钛(II)配位络合物的电子结构和磁性
DOI：
10.1021/acs.inorgchem.0c00311
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发表时间：
2020
影响因子：
4.6
通讯作者：
Telser, Joshua
中科院分区：
文献类型：
--
作者：
Zolnhofer, Eva M.;Wijeratne, Gayan B.;Jackson, Timothy A.;Fortier, Skye;Heinemann, Frank W.;Meyer, Karsten;Krzystek, J.;Ozarowski, Andrew;Mindiola, Daniel J.;Telser, Joshua
稳定的配合物的钛（3d 2）是相对罕见的，但感兴趣的低氧化态钛配合物作为潜在的催化剂和有机合成试剂的应用程序作为配体。具体而言，由氧化还原非活性配体支持的高自旋TiIII离子由于这种软离子的还原能力而仍然非常罕见。在这些配合物中，有反式-[TiCl_2（tmeda）_2]，其中tmeda =N，N，N′，N′-四甲基乙烷-1，2-二胺。Gambarotta及其同事在大约30年前首次报道了这种复合物，但当时它没有光谱特征，量子化学理论（QCT）的理论研究也不可行。作为我们在低氧化态的早期过渡金属配合物的兴趣的一部分，我们已经重新审视了这个复杂的，并报告了一个修改后的合成和低温（100 K）晶体结构，略有不同，从最初报道在环境温度下。我们已经使用了磁强计，高频和场EPR（HFEPR），和可变温度可变场磁圆二色性（VTVH-MCD）光谱来表征transzetrans-[TiCl 2（tmeda）2]。这些技术产生了以下S = 1的自旋哈密顿参数：D= −5.23（1）cm-1，E= −0.88（1）cm-1，（E/D= 0.17），g= [1.86（1），1.94（2），1.77（1）]。这些信息与MCD的电子跃迁相结合，被用作经典配体场理论（LFT）和详细QCT研究的输入，后者包括密度泛函理论（DFT）和从头算方法。这些计算方法很少应用于顺磁性的前过渡金属配合物，特别是那些与S> 1/2。我们的研究提供了一个完整的图片，这个复杂的电子结构，可以放入上下文与其他几个高自旋和单核钛物种的特点。
Stable coordination complexes of TiII(3d2) are relatively uncommon, but are of interest as synthons for low oxidation state titanium complexes for application as potential catalysts and reagents for organic synthesis. Specifically, high-spin TiIIions supported by redox-inactive ligands are still quite rare due to the reducing power of this soft ion. Among such TiIIcomplexes istrans-[TiCl2(tmeda)2], where tmeda =N,N,N′,N′-tetramethylethane-1,2-diamine. This complex was first reported by Gambarotta and co-workers almost 30 years ago, but it was not spectroscopically characterized and theoretical investigation by quantum chemical theory (QCT) was not feasible at that time. As part of our interest in low oxidation state early transition metal complexes, we have revisited this complex and report a modified synthesis and a low temperature (100 K) crystal structure that differs slightly from that originally reported at ambient temperature. We have used magnetometry, high-frequency and -field EPR (HFEPR), and variable-temperature variable-field magnetic circular dichroism (VTVH-MCD) spectroscopies to characterizetrans-[TiCl2(tmeda)2]. These techniques yield the followingS= 1 spin Hamiltonian parameters for the complex:D= −5.23(1) cm–1,E= −0.88(1) cm–1, (E/D= 0.17),g= [1.86(1), 1.94(2), 1.77(1)]. This information, in combination with electronic transitions from MCD, was used as input for both classical ligand-field theory (LFT) and detailed QCT studies, the latter including both density functional theory (DFT) andab initiomethods. These computational methods are seldom applied to paramagnetic early transition metal complexes, particularly those withS> 1/2. Our studies provide a complete picture of the electronic structure of this complex that can be put into context with the few other high-spin and mononuclear TiIIspecies characterized to date.