Zacharopoulos Nikolaos, Schnakenburg Gregor, Panagopoulou Eleni I, Thomaidis Nikolaos S, Philippopoulos Athanassios I
Laboratory of Inorganic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis Zografou, 15771 Athens, Greece.
Institut für Anorganische Chemie, Rheinische Friedrich-Wilhelms-Universität Bonn, Gerhard-Domagk-Straße 1, D-53121 Bonn, Germany.
Molecules. 2025 Jul 11;30(14):2945. doi: 10.3390/molecules30142945.
Searching for new and efficient transfer hydrogenation catalysts, a series of new organometallic ruthenium(II)-arene complexes of the formulae [Ru(η--cymene)(L)Cl][PF] (-) and [Ru(η--cymene)(L)Cl][Ru(η--cymene)Cl] (-) were synthesized and fully characterized. These were prepared from the reaction of pyridine-quinoline and biquinoline-based ligands (L) with [Ru(η--cymene)(μ-Cl)Cl], in 1:2 and 1:1, metal (M) to ligand (L) molar ratios. Characterization includes a combination of spectroscopic methods (FT-IR, UV-Vis, multi nuclear NMR), elemental analysis and single-crystal X-ray crystallography. The pyridine-quinoline organic entities encountered, were prepared in high yield either via the thermal decarboxylation of the carboxylic acid congeners, namely 2,2'-pyridyl-quinoline-4-carboxylic acid (), 8-methyl-2,2'-pyridyl-quinoline-4-carboxylic acid (), 6'-methyl-2,2'-pyridyl-quinoline-4-carboxylic acid () and 8,6'-dimethyl-2,2'-pyridyl-quinoline-4-carboxylic acid (), affording the desired ligands , and , or by the classical Friedländer condensation, to yield 4,6'-dimethyl-2,2'-pyridyl-quinoline () and 4-methyl-2,2'-pyridyl-quinoline (), respectively. The solid-state structures of complexes -, and were determined showing a distorted octahedral coordination geometry. The unit cell of contains two independent molecules (Ru-), (Ru'-) in a 1:1 ratio, due to a slight rotation of the arene ring. All complexes catalyze the transfer hydrogenation of acetophenone, using 2-propanol as a hydrogen donor in the presence of KOPr. Among them, complexes and bearing methyl groups at the 8 and 4 position of the quinoline moiety, convert acetophenone to 1-phenylethanol quantitatively, within approximately 10 min with final TOFs of 1600 h. The catalytic performance of complexes -, towards the transfer hydrogenation of -substituted acetophenone derivatives and benzophenone, ranges from moderate to excellent. An inner-sphere mechanism has been suggested based on the detection of ruthenium(II) hydride species.
为寻找新型高效的转移氢化催化剂，合成并全面表征了一系列通式为[Ru(η⁶ - 对异丙基苯)(L)Cl][PF₆]⁻和[Ru(η⁶ - 对异丙基苯)(L)Cl][Ru(η⁶ - 对异丙基苯)Cl]⁻的新型有机金属钌(II)-芳烃配合物。这些配合物由吡啶 - 喹啉和联喹啉基配体(L)与[Ru(η⁶ - 对异丙基苯)(μ - Cl)Cl]按金属(M)与配体(L)的摩尔比1:2和1:1反应制备而成。表征方法包括多种光谱方法(傅里叶变换红外光谱、紫外 - 可见光谱、多核核磁共振)、元素分析和单晶X射线晶体学。所遇到的吡啶 - 喹啉有机实体，通过羧酸同系物的热脱羧反应，即2,2'-吡啶基 - 喹啉 - 4 - 羧酸、8 - 甲基 - 2,2'-吡啶基 - 喹啉 - 4 - 羧酸、6'-甲基 - 2,2'-吡啶基 - 喹啉 - 4 - 羧酸和8,6'-二甲基 - 2,2'-吡啶基 - 喹啉 - 4 - 羧酸，以高产率制备得到所需配体，或者通过经典的Friedländer缩合反应，分别得到4,6'-二甲基 - 2,2'-吡啶基 - 喹啉和4 - 甲基 - 2,2'-吡啶基 - 喹啉。配合物 - 、 和 的固态结构经测定显示出扭曲的八面体配位几何构型。 的晶胞中由于芳烃环的轻微旋转，包含两个以1:1比例的独立分子(Ru - )、(Ru'- )。所有配合物在KOPr存在下，以2 - 丙醇作为氢供体催化苯乙酮的转移氢化反应。其中，在喹啉部分的8位和4位带有甲基的配合物 和 ，在约10分钟内将苯乙酮定量转化为1 - 苯乙醇，最终的转化频率为1600 h⁻¹。配合物 - 对α - 取代苯乙酮衍生物和二苯甲酮的转移氢化反应的催化性能从中等至优异不等。基于氢化钌(II)物种的检测提出了一种内球机制。
