One-pot synthesis of symmetric and asymmetric p-quinone ligands and unprecedented substituent induced reactivity in their dinuclear ruthenium complexes.
One-pot synthesis of symmetric and asymmetric p-quinone ligands and unprecedented substituent induced reactivity in their dinuclear ruthenium complexes.
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对称和不对称对醌配体的一锅合成以及前所未有的取代基在其双核钌配合物中诱导反应性。
作者：
David Schweinfurth;H. S. Das;Fritz Weisser;Denis Bubrin;B. Sarkar
化合物2-[2-(三氟甲基)-苯胺基]-5-羟基-1,4-苯醌(L(1))、2,5-二-[2-(三氟甲基)-苯胺基]-1,4-苯醌(L(2))、2-[2-(甲硫基)-苯胺基]-5-羟基-1,4-苯醌(L(3))，和通过将2,5-二羟基-1,4-苯醌与相应的胺在回流乙酸中进行一锅合成，高产率地制备了2,5-二-[2-(甲硫基)-苯胺基]-1,4-苯醌(L(4))。这种简单且“绿色”的合成方法以一种罕见、简单的一步过程提供了生物学相关的不对称对醌，例如 L(1) 和 L(3)。所提出的合成路线是通用的，可用于生成各种氮原子上具有不同取代基的分子。 L(2) 和 L(4) 的结构表征显示了分子“上部”和“下部”部分的电子离域，从而显示了电荷分离物质在正确描述此类分子中的重要性。这些配体与 [Cl(η(6)-Cym)Ru(μ-Cl)(2)Ru(η(6)-Cym)Cl] (Cym = p-Cymene = 1-异丙基-4-甲基-苯) 在碱存在下发生反应，导致形成络合物 [{Cl(η(6)-Cym)Ru}(2)(μ-L(-2H)(1))] (1), [{Cl(η(6)-Cym)Ru}(2)(μ-L(-2H)(2))] (2)、[{Cl(η(6)-Cym)Ru}(2)(μ-L(-2H)(3))] (3) 和 [{Cl(η(6)-Cym)Ru}(2)(μ-L(-2H)(4))] (4)。 2和4的结构表征显示了氯原子的罕见顺配位。 3和4中的SMe基团不与钌中心配位，因此桥连配体以双齿形式起作用。这些配合物中的氯原子与 CH(3)CN 中的 AgClO(4) 的抽象结果预期形成溶剂取代的配合物 [{(CH(3)CN)(η(6)-Cym)Ru}(2)(μ-L(-2H)(1))][ClO(4)](2) (5[ClO(4)](2)) 和[{(CH(3)CN)(η(6)-Cym)Ru}(2)(μ-L(-2H)(2))][ClO(4)](2) (6[ClO(4)](2)) 与配体，其中氮取代基上没有额外的供体原子。在 3 和 4 的情况下，相同的氯化物提取反应导致前所未有的取代基诱导的 Cym 配体释放，产生 [(CH(3)CN)(η(6)-Cym)Ru(μ-L(-2H)(3))Ru(CH(3)CN)(3)][ClO(4)](2) (7[ClO(4)](2)) 形式的复合物和[{(CH(3)CN)(3)Ru}(2)(μ-L(-2H)(4))][ClO(4)](2) (8[ClO(4)](2))，其中 SMe 基团现在与金属中心配位。对于含有不对称桥连配体的复合物 3，仅在含有额外 SMe 供体的一侧观察到 Cym 释放，从而证明了此类供体取代基对于观察到的反应性的必要性。氯化物提取时钌中心路易斯酸度的增加是导致 SMe 配位和配体系统刚性的原因，并且它们伴随的未能以钢琴凳配置所需的“fac”方式配位导致最终 Cym 释放。然后桥配体在 8[ClO(4)](2) 中以双子午线方式配位，导致双钳型配位。这些观察结果通过 8[ClO(4)](2) 的结构分析得到验证。结果显示了 L(3) 和 L(4) 等配体的潜在半不稳定特性。报道了 8[ClO(4)](2) 的电化学和光谱研究，并提出了 CH(3)CN 分子的取代反应，以表明 8[ClO(4)](2) 作为其他反应的多功能前体的用途。
The compounds 2-[2-(trifluoromethyl)-anilino]-5-hydroxy-1,4-benzoquinone (L(1)), 2,5-di-[2-(trifluoromethyl)-anilino]-1,4-benzoquinone (L(2)), 2-[2-(methylthio)-anilino]-5-hydroxy-1,4-benzoquinone (L(3)), and 2,5-di-[2-(methylthio)-anilino]-1,4-benzoquinone (L(4)) were prepared in high yields by reacting 2,5-dihydroxy-1,4-benzoquinone with the corresponding amines in a one-pot synthesis in refluxing acetic acid. This straightforward and "green" synthesis delivers biologically relevant asymmetric p-quinones such as L(1) and L(3) in a rare, simple, one-step process. The proposed synthetic route is general and can be applied to generate a variety of such molecules with different substituents on the nitrogen atoms. Structural characterization of L(2) and L(4) shows electron delocalization across the "upper" and "lower" parts of the molecule, thus showing the importance of charge separated species in the proper description of such molecules. Reactions of these ligands with [Cl(η(6)-Cym)Ru(μ-Cl)(2)Ru(η(6)-Cym)Cl] (Cym = p-Cymene = 1-isopropyl-4-methyl-benzene) in the presence of a base result in the formation of complexes [{Cl(η(6)-Cym)Ru}(2)(μ-L(-2H)(1))] (1), [{Cl(η(6)-Cym)Ru}(2)(μ-L(-2H)(2))] (2), [{Cl(η(6)-Cym)Ru}(2)(μ-L(-2H)(3))] (3), and [{Cl(η(6)-Cym)Ru}(2)(μ-L(-2H)(4))] (4). Structural characterization of 2 and 4 shows a rare syn-coordination of the chloride atoms. The SMe groups in 3 and 4 are not coordinated to the ruthenium center, and the bridging ligands thus function in a bis-bidentate form. Abstraction of the chloride atoms in these complexes with AgClO(4) in CH(3)CN results in the expected formation of solvent substituted complexes [{(CH(3)CN)(η(6)-Cym)Ru}(2)(μ-L(-2H)(1))][ClO(4)](2) (5[ClO(4)](2)) and [{(CH(3)CN)(η(6)-Cym)Ru}(2)(μ-L(-2H)(2))][ClO(4)](2) (6[ClO(4)](2)) with the ligands where there are no additional donor atoms on the nitrogen substituents. The same chloride abstraction reaction in the cases of 3 and 4 leads to an unprecedented substituent induced release of the Cym ligand, resulting in complexes of the form [(CH(3)CN)(η(6)-Cym)Ru(μ-L(-2H)(3))Ru(CH(3)CN)(3)][ClO(4)](2) (7[ClO(4)](2)) and [{(CH(3)CN)(3)Ru}(2)(μ-L(-2H)(4))][ClO(4)](2) (8[ClO(4)](2)), where the SMe groups are now coordinated to the metal center. In the case of complex 3, which contains an asymmetric bridging ligand, Cym release is observed only at the side that contains an additional SMe donor, thus proving the necessity of such donor substituents for the observed reactivity. The increase in Lewis acidity at the ruthenium center on chloride abstraction is made responsible for SMe coordination and the rigidity of the ligand systems, and their concomitant failure to coordinate in a "fac" manner as is required for a piano stool configuration results in the eventual Cym release. The bridging ligand which then coordinates in a bis-meridional fashion in 8[ClO(4)](2) results in a bis-pincer type of coordination. These observations were validated by a structural analysis of 8[ClO(4)](2). The results show the potential hemilabile character of ligands such as L(3) and L(4). Electrochemical and spectroscopic investigations are reported on 8[ClO(4)](2), and substitution reactions of the CH(3)CN molecules are presented to show the use of 8[ClO(4)](2) as a versatile precursor for other reactions.