Université Joseph Fourier Grenoble 1/CNRS, Département de Chimie Moléculaire, UMR-5250, Laboratoire de Chimie Inorganique Redox, Institut de Chimie Moléculaire de Grenoble FR-CNRS-2607, BP-53, 38041 Grenoble Cedex 9, France.
Dalton Trans. 2012 Oct 28;41(40):12586-94. doi: 10.1039/c2dt31222k.
The structural, spectroscopic, redox properties and also the reactivity toward S-alkylation of a new mononuclear N2S2 dithiolate Co(II) complex [CoL] (1), with H(2)L = 2,2'-(2,2'-bipyridine-6,6'-diyl)bis(1,1-diphenylethanethiol), have been investigated. The X-ray structure of 1 has revealed an unusual distorted square planar geometry for a Co(II) ion within a thiolate environment. The X-band EPR spectrum of displays a rhombic S = 1/2 signal consistent with a low spin configuration for the d(7) Co(II) ion with a large g-anisotropy (g(x) = 2.94, g(y) = 2.32 and g(z) = 2.01). By pulsed EPR experiments (HYSCORE), two weak hyperfine couplings (hfc) of 3.2 and 2.2 MHz have been measured and attributed respectively to protons and nitrogen nuclei of the bipyridine unit. In addition, another hyperfine coupling (hfc) of 7.5 MHz has been attributed to the cobalt ion. DFT calculations have successfully reproduced the (59)Co and (14)N hfc parameters. However, multiconfigurational ab initio calculations were required to predict the g-tensor of 1. The cyclic voltammogram (CV) displays two one-electron metal based processes: a quasi-reversible Co(III)/Co(II) oxidation wave at E(1/2) = -0.5 V vs. Fc(+)/Fc and a quasi-reversible Co(II)/Co(I) reduction wave at E(1/2) = -1.7 V. 1 reacts with CH(3)I, generating the mono S-methylated complex, [CoL(Me)I] (1(Me)). The X-band EPR spectrum of 1(Me) displays a typical signal of a high spin (S = 3/2) Co(II) species. An optimized structure of 1(Me), calculated by DFT, is consistent with its EPR and UV-visible spectra. Time dependent density functional theory (TD-DFT) calculations attribute the most prominent features observed in the electronic absorption spectra of 1 and 1(Me). The singly occupied MO (SOMO) of 1 shows a notable delocalization of the unpaired electron over the metal (85%) and the ligand, especially over the sulphur atoms (10.5%), indicating a certain degree of covalency for the Co-S bonds. In 1(Me), for two of the three SOMOs, the unpaired electron is notably delocalized over the metal (78.5 and 77.6%, respectively) and the ligand (12.5 and 7.8%, respectively over the sulphur of the thiolate function). For the third SOMO, the unpaired electron is mainly localized on the metal (92.2%). There is no electronic density spread on the sulphur atom of the thioether function in any of these SOMOs. The reactivity and the electronic properties of 1 are also compared with those of the analogous [ZnL] and [NiL] complexes.
研究了一种新的单核 N2S2 二硫代 Co(II) 配合物[CoL]（1）的结构、光谱、氧化还原性质以及对 S-烷基化的反应性，其中 H(2)L = 2,2'-(2,2'-联吡啶-6,6'-二基)双(1,1-二苯基乙硫醇)。1 的 X 射线结构揭示了 Co(II)离子在硫醇环境中呈现出异常的扭曲正方形平面几何形状。X 波段 EPR 谱显示出一个菱形 S = 1/2 信号，与 d(7)Co(II)离子的低自旋构型一致，具有较大的 g 各向异性（g(x) = 2.94，g(y) = 2.32 和 g(z) = 2.01）。通过脉冲 EPR 实验（HYSCORE），测量到两个弱的超精细耦合（hfc）分别为 3.2 和 2.2 MHz，并分别归因于联吡啶单元的质子和氮核。此外，另一个超精细耦合（hfc）为 7.5 MHz，归因于钴离子。DFT 计算成功地再现了(59)Co 和(14)N hfc 参数。然而，需要多组态从头算来预测 1 的 g 张量。循环伏安法（CV）显示了两个基于金属的单电子过程：Co(III)/Co(II)氧化波在 E(1/2) = -0.5 V 相对于 Fc(+)/Fc，Co(II)/Co(I)还原波在 E(1/2) = -1.7 V。1 与 CH(3)I 反应，生成单 S-甲基化配合物[CoL(Me)I]（1(Me)）。1(Me)的 X 波段 EPR 谱显示出典型的高自旋（S = 3/2）Co(II)物种信号。通过 DFT 计算得到的 1(Me)的优化结构与其 EPR 和 UV-可见光谱一致。时间相关密度泛函理论（TD-DFT）计算将 1 和 1(Me)在电子吸收光谱中观察到的最显著特征归因于。1 的单占据 MO（SOMO）显示出未配对电子在金属（85%）和配体上的显著离域，特别是在硫原子上（10.5%），表明 Co-S 键具有一定程度的共价性。在 1(Me)中，对于三个 SOMO 中的两个，未配对电子明显离域在金属（分别为 78.5%和 77.6%）和配体（分别为硫代硫醇功能的 12.5%和 7.8%）上。对于第三个 SOMO，未配对电子主要定域在金属上（92.2%）。在任何这些 SOMO 中，硫醚官能团上的硫原子上都没有电子密度分布。1 的反应性和电子性质也与类似的[ZnL]和[NiL]配合物进行了比较。
